MILITARY HMMWV - FMTV Sales, LLC

AM General Corporation

MILITARYHMMWV

M998A1 Series Vehicles

Component Testing and Troubleshooting

5715434

AM General CorporationTraining DepartmentP.O. Box 728408 South Byrkit StreetMishawaka, IN 46546-0728 USAPhone: (219) 258-6624Fax: (219) 254-2260

January 1995Revised October, 1996Copyright

®

1999, AM General Corporation

This publication, or parts thereof, may not be reproduced in any form, by any method, for any purpose without written permission from AM General Corporation.

Page I

ContentsSECTION 1 COOLING SYSTEM

A. FAN CLUTCH TEST PROCEDURE ..................................................................... 1-1B. FAN THERMOSTATIC SWITCH TESTING .......................................................... 1-1C. FAN CLUTCH SOLENOID RESISTANCE TEST .................................................. 1-2D. FAN CLUTCH VALVE PRESSURE TEST............................................................ 1-3E. FAN CLUTCH PRESSURE TEST ........................................................................ 1-3F. ATTACHING COOLANT PRESSURE TESTER.................................................... 1-4G. RADIATOR EXTERNAL PRESSURE LEAK TESTING ........................................ 1-5H. RADIATOR INTERNAL PRESSURE LEAK TESTING ......................................... 1-5I. HEAD GASKET LEAK TEST ................................................................................ 1-6J. COMPRESSION OR COMBUSTION LEAK TEST ............................................... 1-6K. TESTING THE PRESSURE CAP ......................................................................... 1-7L. READING THE GAGE .......................................................................................... 1-9M. FAN SHROUD ADJUSTMENT ........................................................................... 1-10N. ENGINE COOLING SYSTEM FLOW OIL/COOLANT ....................................... 1-10O. ENGINE NORMAL OIL FLOW SCHEMATIC...................................................... 1-11

SECTION 2 AIR INTAKE AND EXHAUST SYSTEMS

A. MANOMETER INTAKE RESTRICTION TEST ..................................................... 2-1B. ENGINE STOPS DURING NORMAL OPERATION ............................................. 2-1

SECTION 3 FUEL SYSTEM

A. 6.2L V8 DIESEL ENGINE ..................................................................................... 3-1B. DIAGNOSING ABNORMAL ENGINE OPERATION ............................................. 3-2C. BLACK OR WHITE SMOKE COMING FROM EXHAUST .................................... 3-4D. BLUE SMOKE COMING FROM EXHAUST ........................................................ 3-5E. DIESEL ENGINE KNOCK .................................................................................... 3-5F. ENGINE HARD STARTING (HOT) ....................................................................... 3-5G. ENGINE HARD STARTING (COLD) ..................................................................... 3-5H. FUEL SYSTEM FLOW SCHEMATIC.................................................................... 3-7I. TROUBLESHOOTING AND TESTING ................................................................. 3-9J. ELECTRICAL FUEL SOLENOID CHECK ............................................................ 3-9K. COLD ADVANCED SOLENOID CHECK .............................................................. 3-9L. CHECKING HOUSING PRESSURE COLD ADVANCE SWITCH ........................ 3-9M. FUEL INJECTION PUMP TEST ........................................................................... 3-9N. UNDERSTANDING DIESEL FUEL ..................................................................... 3-10O. TYPICAL FUEL PROPERTIES ......................................................................... 3-11P. ENGINE CRANKING SPEED TEST................................................................... 3-11Q. FUEL PUMP PRESSURE TEST ........................................................................ 3-11R. FUEL FILTER...................................................................................................... 3-12S . FUEL ECONOMY ............................................................................................... 3-12

Page II

SECTION 3 FUEL SYSTEM (Continued)

T. FUEL FILTER PRESSURE TEST....................................................................... 3-12U. FUEL FILTER FLOW TEST ................................................................................ 3-13V. FUEL TANK CONTAMINATION TEST ................................................................ 3-13W. FUEL INJECTION PUMP TEST ......................................................................... 3-13X. FUEL INJECTOR NOZZLE TEST (TEST STAND) ............................................. 3-15Y. FUEL INJECTOR NOZZLE TEST (IN VEHICLE) ............................................... 3-16Z. 6.2L INJECTION NOZZLE RETURN HOSE ...................................................... 3-16AA. FUEL SOLENOID TEST - ENGINE CRANKS BUT WILL NOT START .............. 3-17BB. COLD ADVANCE SOLENOID-SWITCH TEST ................................................... 3-18CC. INJECTION PUMP AIR PRESSURE TEST ....................................................... 3-19DD. INJECTOR LINE LENGTH ................................................................................. 3-19EE. WATER IN INJECTOR PUMP ............................................................................ 3-19FF. FUEL RETURN VALVE TEST ............................................................................. 3-20GG. FUEL SHUTOFF SOLENOID TEST (Figure 3-9) ............................................... 3-20HH. DIESEL FUEL QUALITY .................................................................................... 3-21JJ. DIESEL FUEL CONTAMINATION ...................................................................... 3-22KK. DIESEL FUEL SYSTEM CLEANING PROCEDURE.......................................... 3-23LL. CLEANING PROCEDURE: GASOLINE IN FUEL .............................................. 3-24MM. FUEL FLOW TEST ............................................................................................. 3-24NN. VACUUM TEST FUEL LIFT PUMP INLET ........................................................ 3-25OO. MECHANICAL FUEL PUMP TESTS .................................................................. 3-25

SECTION 4 ENGINE

A. GENERAL ENGINE DATA .................................................................................... 4-1B. MANOMETER - BLOW-BY TEST ......................................................................... 4-2C. GLOW PLUG TIP REMOVAL (DAMAGED OR BROKEN).................................... 4-2D. ENGINE INJECTION PUMP TIMING PROCEDURES

USING KENT-MOORE TACH-N-TIME METER .................................................... 4-3a. Connecting Power Leads ................................................................................ 4-4b. Enter Offset Chart ........................................................................................... 4-5c. Injection Pump Timing Adjustment .................................................................. 4-6d. Engine Injection Pump Timing ......................................................................... 4-7

E. ENGINE INJECTION PUMP TIMING PROCEDURESUSING SNAP-ON LUMY/MAG II TIMING ............................................................ 4-8a. Accessories Included with the MT-1480 .......................................................... 4-9b. Display Codes ............................................................................................... 4-10c. Operator Tips................................................................................................. 4-11c. Equipment Tips ............................................................................................. 4-11e. Checking Cranking Speed............................................................................. 4-12f. Hookup Procedures and Testing Tips ............................................................ 4-12g. Diesel Engine Timing .................................................................................... 4-13h. Injection Pump Timing Adjustment LUMY/MAG II ......................................... 4-14i. Cranking RPM Test........................................................................................ 4-16j. Enter Offset Chart ......................................................................................... 4-17

F. USE OF TORQUE COMPUTER......................................................................... 4-18

Page III

SECTION 4 ENGINE (Continued)

G. ENGINE COMPRESSION TEST ........................................................................ 4-19H. CHECK FOR ENGINE MECHANICAL OR HYDRAULIC SEIZURE................... 4-20I. PRE-CHAMBER CRACKS ................................................................................. 4-20J. NOISY VALVES & VALVE SPRING CHECK ....................................................... 4-21K. VALVE LIFTER DIAGNOSIS .............................................................................. 4-21L. V-8 DIESEL HEAD GASKET LEAKAGE ........................................................... 4-22M. LEAKING CYLINDER HEAD GASKET .............................................................. 4-22N. DIESEL HEAD GASKET PRE-INSTALLATION INSPECTION ........................... 4-23

SECTION 5 BRAKES

A. WHAT IS HYDRO-BOOST? ................................................................................. 5-1B. WHY HYDRO-BOOST?........................................................................................ 5-1C. HYDRO-BOOST II ................................................................................................ 5 - 2D. TROUBLESHOOTING .......................................................................................... 5-3E. SEAL LEAKSF. HYDRO-BOOST DIAGNOSIS .............................................................................. 5-6

a. Booster Functional Test ................................................................................... 5-6b. Leakdown Test ................................................................................................. 5-9

G. PARKING BRAKE LIGHT SWITCH TEST ............................................................ 5-9H. BLEEDING THE HYDRO-BOOST SYSTEM ...................................................... 5-10I. BRAKE FLUID .................................................................................................... 5-10

SECTION 6 TRANSMISSION

A. MODULATOR MAINTENANCE AND ADJUSTMENT .......................................... 6-1B. TRANSMISSION OIL PRESSURE TESTS .......................................................... 6-2C. TRANSMISSION CONTROL VALVE AND GOVERNOR PRESSURE TEST ....... 6-6D. TRANSMISSION ROAD TEST ............................................................................. 6-7E. TRANSMISSION DETENT SOLENOID RESISTANCE TEST .............................. 6-7F. TRANSMISSION KICK-DOWN SWITCH TEST & ADJUSTMENT....................... 6-8G. TRANSMISSION MALFUNCTIONS ..................................................................... 6-9

Malfunction 1. No 1-2 Upshift or Delayed Upshift .............................................. 6-9Malfunction 2. 1-2 Shift or Slips ........................................................................ 6-10Malfunction 3. 1-2 Shift Firm or Rough............................................................. 6-11Malfunction 4. No 2-3 Upshift or Delayed Ups ................................................. 6-11Malfunction 5. 2-3 Shift Soft or Slips ................................................................ 6-11Malfunction 6. 2-3 Shift Firm or Rough............................................................. 6-12Malfunction 7. No Engine Braking - Second Gear ............................................ 6-12Malfunction 8. No Engine Braking - First Gear ................................................. 6-12Malfunction 9. No Detent Downshifts ............................................................... 6-13Malfunction 10. No Drive or Drive Slips .............................................................. 6-13Malfunction 11. No Reverse or Reverse Slips .................................................... 6-13Malfunction 12. Vehicle Moves in Neutral ........................................................... 6-14Malfunction 13. Transmission Noisy ................................................................... 6-14

Page IV

SECTION 6 TRANSMISSION (Continued)

H. TORQUE CONVERTER END PLAY CHECK ..................................................... 6-14J. TORQUE CONVERTER LEAK TEST ................................................................. 6-16

SECTION 7 ALIGNMENT PROCEDURES

A. TOE-IN/FRONT WHEEL CHECK AND INSPECTION ........................................ 7-1a. Preliminary Inspectionb. Ball Joint Inspection .......................................................................................... 7-2c. Idler Arm Inspection .......................................................................................... 7-3d. Toe-In Check ..................................................................................................... 7-6e. Toe-In Adjustment ............................................................................................. 7-9

B. TOE-OUT REAR WHEEL CHECK ADJUSTMENT ............................................ 7-10a. Preliminary Inspection ................................................................................... 7-10b. Toe-Out Check .............................................................................................. 7-11c. Toe-Out Adjustment....................................................................................... 7-14

C. STEERING STOP CHECK & ADJUSTMENT .................................................... 7-15a. Removal ........................................................................................................ 7-15b. Installation ..................................................................................................... 7-15c. Adjustment .................................................................................................... 7-15

D. CASTER & CAMBER CHECK ANDADJUSTMENT PROCEDURES ......................................................................... 7-17a. Caster and Camber Check ............................................................................ 7-17b. Caster and Camber Adjustment .................................................................... 7-18

SECTION 8 JACKING PROCEDURES

A. RAISING CORNER OF VEHICLE ........................................................................ 8-2B. LOWERING CORNER OF VEHICLE ................................................................... 8-2C. RAISING FRONT OF VEHICLE ........................................................................... 8-2D. LOWERING FRONT OF VEHICLE....................................................................... 8-2E. RAISING REAR OF VEHICLE .............................................................................. 8-4F. LOWERING REAR OF VEHICLE ......................................................................... 8-4G. RAISING ENTIRE VEHICLE ................................................................................ 8-4H. LOWERING ENTIRE VEHICLE ............................................................................ 8-4

SECTION 9 POWER STEERING

A. POWER STEERING TEST & BLEEDING ............................................................ 9-1

SECTION 10 TRANSFER CASE

A. TRANSFER CASE HOUSING STUDS............................................................... 10-1B. TRANSFER CASE TOWING INSTRUCTIONS .................................................. 10-1

Page V

SECTION 11 DIFFERENTIALS

A. AXLE AND DIFFERENTIAL OPERATION.......................................................... 11-1B. OPERATING PRINCIPLE ................................................................................... 11-2

SECTION 12 ELECTRICAL SYSTEM

A. BATTERY SHUNT TEST AND REPLACEMENT.................................................... 12-1B. STARTER TESTING ............................................................................................... 12-1C. BATTERY CIRCUIT CHECKS ................................................................................ 12-3D. 6.2L ENGINE GLOW PLUG SYSTEM ................................................................... 12-4

a. Glow Plug System Continues To Cycle After Engine Is Warmed Up............. 12-5b. Checking glow plug internal resistance using Multimeter.............................. 12-5

E. COLD START ADVANCE DOES NOT FUNCTION PROPERLY ............................ 12-7F. NIEHOFF 100 AMP ALTERNATOR TESTING . ...................................................... 12-8

a. On Vehicle Test .............................................................................................. 12-8b. Preliminary Checks ....................................................................................... 12-8c. Test Setup ..................................................................................................... 12-9d. Test Procedure ............................................................................................ 12-10e. Static Checks: Partially Disassembled Alternator ....................................... 12-11f. Field Coil Test .............................................................................................. 12-11g. Electrical Continuity Check.......................................................................... 12-12h. Diode Heatsink Test..................................................................................... 12-12i. Stator Tests.................................................................................................. 12-13

I. PROTECTIVE CONTROL BOX TESTING............................................................. 12-15J. LIGHT TESTING ................................................................................................... 12-17K. HIGH BEAM SELECTOR SWITCH TESTING .................................................... 12-19L. STOPLIGHTS INOPERATIVE OR DO NOT OPERATE PROPERLY .................. 12-20M. TURN SIGNALS INOPERATIVE OR DO NOT OPERATE PROPERLY............... 12-20N. ONE OR MORE TRAILER LIGHTS INOPERATIVE (VEHICLE LIGHTING SYSTEM FUNCTIONS NORMALLY) .............................. 12-23O. WARN 6000 POUND , 24 VDC WINCH

ELECTRICAL TROUBLESHOOTING PROCEDURES ................................... 12-25a. Power Supply .............................................................................................. 12-25b. Grounding.................................................................................................... 12-25c. Electronic Current Limiter (ECL) ................................................................. 12-26d. Thermal Switch ........................................................................................... 12-27e. M o t o r ................................................................................................ 12-28

SECTION 13 TIME DELAY MODULE OPERATION

A. TIME DELAY MODULE OPERATION................................................................. 13-2B. TIME DELAY MODULE OPERATION................................................................. 13-3C. TIME DELAY MODULE OPERATION................................................................. 13-4D. TIME DELAY MODULE OPERATION................................................................. 13-5

Page VI

SECTION 13 TIME DELAY MODULE OPERATION (Continued)

E. TIME DELAY MODULE OPERATION................................................................. 13-6F. TIME DELAY MODULE OPERATION................................................................. 13-7G. TIME DELAY MODULE TESTING ...................................................................... 13-8

a. Description .................................................................................................... 13-8b. On-Vehicle Testing......................................................................................... 13-9Four Prong Connector ........................................................................................ 13-9Two Prong Connector ......................................................................................... 13-9

H. BENCH TESTING............................................................................................. 13-10

1

Section 1. Cooling System

SECTION 1COOLING SYSTEM

Figure 1-1. Fan Thermostatic Switch Testing Hookup.

A. FAN CLUTCH TEST PROCEDURE

With engine off, attempt to turn fan by hand. Iffan can be turned independently of clutch,replace or repair fan drive.

B. FAN THERMOSTATIC SWITCHTESTING (Figure 1-1)

1. With engine running disconnect engineharness leads 458A (1) and 458B (2) from

fan thermostatic switch harness leads (3)located on the left side of the water crossoverpipe (4). Fan should engage and operate.

2. With engine running momentarily connectengine harness leads 458A & 458B together.Fan should disengage.

FAN THERMOSTATIC(TEMP.) SWITCH

24 VOLTPOWERSOURCE

458 458A

458B458(N.C.)

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HMMWV Component Testing and Troubleshooting

Page 1-2

C. FAN CLUTCH SOLENOIDRESISTANCE TEST (Figure 1-2)

Test for clutch control valve solenoid resistance.Using a multimeter, check resistance between

Figure 1-2. Fan Clutch Solenoid Resistance Test Hookup.

connector terminals (1). Check resistance bothways. Resistance should be 58 ohms to 78ohms both ways. If not, replace drive solenoidand hydraulic control valve assembly and checkfor operation while engine is running.

FAN THERMOSTATIC(TEMP.) SWITCH

24 VOLTPOWERSOURCE

KICK-DOWNSWITCH

TIME DELAYMODULE

FAN CLUTCHSOLENIOD

FANCLUTCH

HYDRAULICCONTROL VALVE(Closes @ 30 PSI)

(Opens @ 30-90 PSI)

458 458A

458B

583B

315C

315D

93

583

93

458

(N.O.)

(N.O.)

(N.C.)

N.O.–Normally OpenN.C.–Normally Closed

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3


D. FAN CLUTCH VALVE PRESSURETEST (Figure 1-3)

With the engine running, measure pressure athydraulic hose (1) from fan control valve to fanshroud fitting. Coolant temperature must bebelow 210°F (99°C). If pressure is below 90 psi(620 kPa), remove hydraulic control valve.Check valve openings for debris which wouldinterfere with control valve operation. Cleancontrol valve openings. Replace control valveif unserviceable.

With engine running, disconnect and measurepressure at hydraulic hose (1) from fan controlvalve to fan shroud fitting. Pressure should bebelow 30 psi (206 kPa). If pressure is above 30psi (206 kPa), remove hydraulic control valve.Check valve openings for debris which wouldinterfere with control valve operation. Cleancontrol valve openings. Replace control valveif unserviceable.

Normal operating pressure for the fan clutchhydraulic control valve is between 90-165 psi(620-1137 kPa).

CAUTION

Pressure required to override fan clutchspring, and allow fan to free-spin isbetween 30-90 psi (260-620 kPa). Pressurein the fan clutch line however, could goup to 165 psi (1137 kPa).

E. FAN CLUTCH PRESSURE TEST(Figure 1-3)

Check fan drive operation. Disconnect hose (1)at fan shroud fitting. Apply 90 psi (620 kPa) airpressure to fan shroud fitting. Fan clutch shoulddisengage. If fan clutch does not disengage,replace or repair fan drive.

Figure 1-3. Fan Clutch Valve Pressure Test Hookup.


Page 1-4

F. ATTACHING COOLANT PRESSURETESTER (Figure. 1-4 and 1-5)

1. Carefully remove the radiator pressure capfrom the surge (overflow) tank.

2. Make sure coolant is at recommended levelin surge tank.

3. Wipe out the inside of the filler neck.Examine the lower inside sealing seat ofthe filler neck for dirt.

4. Inspect the overflow tube for dents or internalobstruction. Pressure released by thepressure cap during operation of the truckmust pass through this tube. An obstructedtube may cause the radiator or some portion

Figure 1-4. Attaching CoolantPressure Tester

of the cooling system to burst if pressurebuilds up excessively.

5. Inspect the cams on the outside of the fillerneck. If cams are bent down or up, theseating of the pressure cap valve and theTester seal will be affected. Bent cams canbe reformed if it is done carefully. DO NOTBREAK THE SOLDER JOINT BETWEENTHE NECK AND THE RADIATOR TOPTANK.

6. Attach the Pressure Tester to the filler neckas shown in Figure 1-4. Set the Tester onthe filler neck with the locking ears in linewith the entrance notches of the filler neck.Press down slightly and rotate clockwiseuntil the locking ears are stopped by thestop lugs on the filler neck. DO NOT FORCE.

5


7. After attaching the Tester to the surge tankfiller neck, operate the pump until theindicator hand on the gauge reaches theproper arrow just beyond the end of eachcolor band.

The Hummer 15-17 POUND SYSTEM, shouldbe pumped up to the lines indicating the 15–17pound system (1), Figure 1-5. DO NOTEXCEED THIS POINT.

WARNING

Never exceed the arrow points of therecommended pressure of the systembeing tested, as it is not necessary to gobeyond the arrow to determine if leaksexist. Excessive pressure can ruptureradiator, hose, etc. Never pressurize intothe red danger area for any coolingsystem as serious damage to it mayoccur.

Figure 1-5. Coolant Tester Gauge.

G. RADIATOR EXTERNAL PRESSURELEAK TESTING (Figure 1-5)

After pumping the proper amount of pressureinto the radiator, observe the gauge.

1. ARROW HOLDS STEADY

If the hand holds steady for two minutes,there are no serious leaks in the system.Nevertheless, examine all points for seepageor slight leakage with a flashlight.

2. ARROW DROPS SLOWLY

Indicates the presence of small leaks orseepage. Check radiator, hose, gaskets,and heater. After repairing leaks, the systemshould be rechecked for minor leaks asthese will quickly become major leaks. Ifradiator hose swells excessively while testingsystem, it indicates it is in a weakenedcondition and should be replaced.

3. ARROW DROPS QUICKLY

Indicates that serious leakage is present.Large radiator leaks should be repaired.

H. RADIATOR INTERNAL PRESSURELEAK TESTING (Figure 1-5)

WHEN THE GAUGE SHOWS A PRESSUREDROP AND THERE IS NO VISIBLE LEAKAGE.Remove tester and replace pressure cap. Runthe engine to churn up the oil and examine thedipstick for water globules. Another methodwould be to remove the crankcase drain plugand drain out a small amount of oil; water beingthe heaviest should drain out first.


Page 1-6

J. COMPRESSION OR COMBUSTIONLEAK TEST (Figure 1-5)

If pressure does not build up immediately thenoperate the Pressure Tester pump until thegage reads within the range for the systembeing tested. If the gage hand vibrates, thisindicates a compression or combustion leakinto the cooling system. Location of compressionleak is determined by shorting out each injector;gage hand will stop or decrease vibrating whenthe injector of the leaking cylinder is shortedout. Retest with Pressure Tester after repairingleak.

Remove Tester From Radiator Neck.(Figure 1-6)

Release pressure in cooling system by pressingstem to one side, (Figure 1-6) then removeTester from filler neck.

I. HEAD GASKET LEAK TEST(Figure 1-5)

Compression or combustion leakage into thecooling system can be detected as follows:

1. Carefully remove the pressure cap andapply the Pressure Tester to the filler neckwhen the engine is cool.

2. Let engine idle and warm up to normaloperating temperature. WATCHCAREFULLY, IF GAGE INDICATESPRESSURE IS BUILDING UP FAST,RELEASE PRESSURE BY TURNINGOFF ENGINE AND CAREFULLYREMOVING TESTER.

3. Do not allow pressure to build up past arrowindicating maximum for the system. Whenpressure builds up fast, a leak exists as aresult of a blown gasket. Replace headgasket.

Figure 1-6. Releasing Cooling System Pressure Tester.

7


K. TESTING THE PRESSURE CAP(Figures 1-7 thru 1-9)

The Pressure Cap functions as a safety valveto keep the pressure within the desired safelimits as designed by the truck manufacturer.The filler cap is stamped or otherwise markedwith a figure indicating the approximateoperating pressure. (See Figure 1-7).

Pressure Caps are designed to operate withina predetermined range as follows:

Pressure Marking Operating Range on Cap

4 (lb) 3–4 lb 7 (lb) 6–8 lb13-14 (lb) 12–16 lb

HMMWV 15-17 (lb) 14 –18 lb

This means that the pressure valve shouldNOT OPEN below the low limit of the range(i.e. 3 lb for 4 lb cap) but MUST OPEN at or

below the top limit of the range (i.e. 4 lb for a4 lb cap). A slight allowance is made on thegage dial of the Tester at the lower end of thecolor band to eliminate the possibility ofrejecting caps that are otherwise satisfactoryas a result of the newness of the seatinggasket. The gasket will soften and develop asatisfactory seat after it is put in operation onthe vehicle filler neck for a short time.

For the same reason, caps removed fromvehicles and tested should be removed fromthe tester adaptor and reapplied several timesas the gasket will retain the seat impression ofthe filler neck for sometime which may notcoincide exactly with the seat in the adaptor onone application.

All Pressure Caps are equipped with a vacuumrelief valve which open automatically as thevehicle engine is cooling off to prevent theformation of a vacuum in the system. Thisprevents the collapse of radiator upper andlower tanks, hose, etc.

Figure 1-7. Pressure Cap Markings


Page 1-8

K. TESTING THE PRESSURE CAP(Cont.) (Figures 1-7 thru 1-9))

1. Carefully remove cap and check thepressure as marked on the top of the cap.Compare it with recommended rating of 14-18 lb (96-124 kPa).

2. Make sure all parts and seating surfaces ofcap and adapter are clean. On safety typecaps be sure lever is in down or closedposition.

3. On new caps, wet the rubber gasket inwater. NOTE: Due to the newness of thegasket, it may be necessary to remove thepressure cap several times to get a propersealing seat on the gasket. The gasketsoftens in actual operation and will workperfectly.

Figure 1-8. Pressure Cap Test Hookup.

4. Attach the pressure cap to be tested, asshown in Figure 1-8, to one end of adapter.Attach opposite end of the adapter to thepressure tester by pressing together androtating adapter until the locking ears contactthe stops on the adapter cams.

5. Hold Tester with gage facing you as shownin Figure 1-9.

6. Operate the pump until needle reaches itshighest point

Figure 1-9. Pressure Cap Test.

NOTE

Remember that a cap that has been inuse on a radiator for some time will havea slight seat impression in the gasket;therefore, the cap (if it leaks) should beremoved and applied several times to theadapter to be sure that leakage is notcaused by the impression not seatingproperly. After the cap is reinstalled onthe vehicle, the continuous springpressure will reseat the gasket properlyin a short time.

9


L. READING THE GAGE(Figures 1-9 & 1-10)

Stop pumping when the valve opens and readthe gage (See Figure 1-9) as follows: The gagehand must be within the proper color band for

Figure 1-10. Tester Gage Readings.

the pressure rating of the cap being testedwhen the pressure valve opens. The cap issatisfactory when the pressure holds steady orfalls very slowly, but holds within the band for 30seconds or more. If the gage hand fallscomparatively fast which indicates seriousleakage, reject the pressure cap.


Page 1-10

M. FAN SHROUD ADJUSTMENT(Figure 1-11)

NOTES

Fan shroud should be alined so thefollowing dimensions are maintained.Adjustments may be made by tilting theradiator/shroud assembly. Clearancebetween top of fan blade and fan shroudmust be 1/2 inch (12.7 mm). Distance “A”from the edge of shroud ring and rearedge of fan must be 1-1/2 inch (38.1 mm).

NOTE

If there is evidence of fan bladeshitting on fan shroud, check for loose ordamaged engine mounts.

Figure 1-11. Fan Shroud Adjustment.

N. ENGINE COOLING SYSTEM FLOWOIL/COOLANT (Figure 1-12)

1. Engine Oil – Engine oil is pumped from theengine pan (10-50 psi), through the engineoil cooler lines to the engine oil cooler whereit is cooled by air flowing through the coolerfins and is returned to the engine throughthe engine oil cooler return line.

2. Transmission Fluid – Transmission fluidis pumped from the transmission to thetransmission oil cooler through an externaltransmission cooler line and is cooled by airflowing through the transmission oil coolerfins. From the transmission oil cooler, fluidis routed to the transfer case internal finnedcooler and on to the transmission through areturn line. The transfer case finned cooleracts as a secondary cooler for transmissionoil and the two oils do not mix.

3. Coolant – engine coolant is pumped fromthe coolant pump through the engine internalcooling jackets, through the thermostat(when open) and returned to the radiator forcooling. When the heater is turned on,coolant is also pumped through lines to theheater and returned to the radiator

=Water

=Oil

Engine

Transmission

TransferCase

PersonnelHeater

SurgeTank

WaterCrossover

Radiator

OilPump

Figure 1-12. Cooling System Schematic.

11


O. ENGINE NORMAL OIL FLOWSCHEMATIC (Figure 1-13)

1. The lubricating system of this engine is apressure feed type which means that apump forces oil through the galleries to thenecessary parts. The pump is mounted onthe bottom side of the rear main bearingcap. Oil is picked up by the oil pickup tubeand pumped through the oil pump. The oilpump is driven by the engine camshaft bymeans of an intermediate shaft.

2..The oil is then pumped through an oilcooler which cools the oil and helps removeengine heat. From the cooler the oil passesthrough a filter. This filter is a cartridge typeand all oil going to the engine should pass

through this filter. The filter is called a fullflow filter, because all engine oil normallyflows through it.

3. Normal average engine oil pressure at stableconditions is 40-50 PSI @ 2000 RPM. Theengine oil filter bypass valve opens at 16-19PSI above normal high (50 PSI), whenincreased pump pressure tries to pump oilthrough a clogged filter. When the bypassvalve opens, the oil bypasses the filter andthe engine continues to receive lubrication.

4. The engine oil cooler also has a bypassvalve. It works the same as the oil filterbypass valve and opens to allow an alternateroute for the oil if the cooler should becomeclogged. The oil cooler bypass valve opensat 9-11 PSI above normal high (50 PSI).

From OilPump

Rocker ArmPush Rod

Cam Bearings

Cooler Bypass Valve

Filter Bypass Valve

Oil Filter

Main Bearing

Valve Lifter

OilCooler

ToOil

Pump

ToOil

Pump

ToOil

Pump

ToOil

Pump

ToOil

Pump

Plug

Alternate Oil Flow Route–Cooler

Alternate Oil Flow Route–Filter

Figure 1-13. Engine Lubrication System Schematic.


Page 1-12

1

Section 2. Air Intake and Exhaust Systems

SECTION 2AIR INTAKE AND

EXHAUST SYSTEMSA. MANOMETER INTAKE RESTRICTION

TEST (Figure 2-1)

Connect manometer tube to air cleaner ventline (1) pipe (Fig. 2-1). Run engine atapproximately 1000 RPM. Water travel shouldnot exceed 3 inches of water travel. If watertravel exceeds 3 inches, check for restriction inair intake system.

B. ENGINE STOPS DURING NORMALOPERATION

a. Check for restriction in air intake system.Check gage on instrument panel. Indicatorshould be in the yellow range. If reading isin the red range, clean and service aircleaner.

b. Check cleaner to air horn elbow and air hornfor damage that would restrict air flow.

c. To test air indicator gage, remove air hose(2) and create a vacuum on tubing. Gage (3)should move into the red position.

Figure 2-1. Manometer Intake Restriction Test.


Page 2-2

C. EXHAUST (Figure 2-2)

Leaking Exhaust Gases orExhaust Noises

1. Check for rusted through or damagedexhaust pipe or muffler.

2. Check for loose or missing exhaust pipeand crossover pipe fasteners.

3. Check for leaking exhaust gaskets.

Exhaust Restrictions

1. Check for bent exhaust pipe.

2. Check for damaged muffler.

EXHAUSTHEADERS

EXHAUSTHEADERS

CROSSOVERPIPE

EXHAUST PIPE/MUFFLER

TAILPIPE

Figure 2-2. Exhaust System.

1

Section 3. Fuel system

SECTION 3FUEL SYSTEM

A. 6.2L V8 DIESEL ENGINE (Figure 3-1)

This engine is a 6.2L, 6217 cc (379.4 cu. in.) V8diesel.

The injection pump used with the 6.2L is thesame basic unit as that used on the Oldsmobile/GMC passenger car and light pickup trucks,namely the Roosa Master Stanadyne modelDB2.

The engine cylinders are numbered 1, 3, 5, and7 on the left bank, and cylinders 2, 4, 6, and 8on the right bank with a firing order of 1-8-7-2-6-5-4-3. The odd-numbered cylinders are on yourright-hand side when viewing the engine fromthe front. Both the cylinder arrangement andthe injection pump fuel line routing are illustratedin Figure 3-1.

Figure 3-1. Cylinder Arrangement and Fuel Line Routing.

Cylinder Arrangement

Fuel Line Routing


Page 3-2

B. DIAGNOSING ABNORMAL ENGINEOPERATION

1. Engine starts, idles roughly without abnormalnoise or smoke.

• Check engine idle.• Inspect fuel injection lines for leaks.• Inspect fuel return lines for restrictions

or leaks.• Check for air in the fuel system.• Inspect fuel system for contamination.

2. Engine cold starts and idles roughly, butidles smoothly after warm-up.

• Check for air in the fuel system.• Check glow plug operation.• Check the cold start advance system.

3. Engine idles smoothly but misfires at higherRPM.

• Inspect fuel filters for contamination orrestriction of flow.

• Check for proper fuel.

4. Engine smokes excessively during normaloperation.

• Make sure all injectors are same length.• Remove and test fuel injectors.• Check fuel system for contamination or

restriction.• Check for restrictions in air intake system.• Check for clogged crankcase depression

regulator valve.• Black exhaust smoke may indicate

excess fuel or restricted air supply.• Blue smoke may indicate oil is being

burned by the engine.• White smoke may indicate unburned fuel

or water vapor.

5. Engine will not return to idle.

• Check external fuel linkage for binding ormisadjustment.

• Check fuel injection pump min-maxgovernor.

6. Engine will not shut off.

• Check injection pump fuel shutoffsolenoid. If shutoff solenoid is inoperative,pinch the pump rubber fuel return line.

3


7. Excessive engine vibration.

• Check for air in the fuel lines.• Check for broken engine mounts and

insulators.• Check for loose or damaged vibration

damper.• Check for sticking injector(s).

8. Engine loses power.

• Check air intake system for restriction orblockage.

• Check for obstructed exhaust system.• Check for clogged fuel filter and fuel

lines.• Check for incorrect fuel or contamination.• Check for plugged fuel tank.• Check for restricted fuel flow from fuel

tank.• Check for external compression leaks.• Check engine/pump timing.• Check mechanical lift pump.

9. Engine will not crank.

• Check for mechanical or hydraulicengine seizure.

• Check the starting system.

10. Engine cranks, but will not start.

• Check engine cranking speed.• Check for incorrect engine oil.• Inspect starting system.• Inspect fuel system.• Check operation of glow plug system.

11. Excessive oil loss or consumption.

• Ensure that proper procedures are usedto check oil.

• Make sure that proper grade of oil isused.

• Inspect engine for leaks at the following:- oil pan- oil filter- dipstick- valve covers- oil cooler and, cooler lines- oil pressure sensor- tighten any loose connections or

replace damaged parts


Page 3-4

C. BLACK OR WHITE SMOKE COMINGFROM EXHAUST

1. Black Smoke:

Black smoke is the most common smokingcomplaint. Diesels are usually rated accordingto the maximum horsepower developed at the“smoke limit.” At a certain speed, a definiteamount of air enters the cylinder. This amountof air is sufficient to produce completecombustion of a given quantity of fuel. If morefuel is injected, overloading the engine beyondthe rated horsepower, there will not be sufficientair for complete combustion and black smokewill result. Under these conditions, the blacksmoke contains a large quantity of unburnedcarbon (soot) formed by thermal decompositionof the fuel in the over-rich mixture in the cylinder.

Some sources of black smoke directly relatedto improper burning of fuel are:

• Air into injection pump• Fuel return restricted• Pump timing advanced (usually will be

accompanied by excess combustionnoise)

• Wrong fuel• Excess fuel delivery from nozzles due to

low opening pressure or stuck nozzle• Restricted exhaust• Low compression• Clogged air inlet

2. White Smoke:

At Iight loads, the average temperature in thecombustion chamber may drop 500°F, due tothe decreased amount of fuel being burned. Asa result of the lower temperature, the fuel

ignites so late that combustion is incomplete atthe time the exhaust valve opens and fuel goesinto the exhaust in an unburned or partiallyburned condition producing the white smoke.Under these conditions, a higher cetane fuel ora more volatile fuel will tend to promote bettercombustion and reduce smoke. Any operatingvariable (jacket temperature, inlet airtemperature, etc.) that increases compressiontemperature or reduces ignition delay willimprove the white smoke problem. White smokeis considered normal when the vehicle is firststarted, but should stop as the vehicle warmsup. A continuing white smoke condition couldindicate a loss of compression. Retarded timingand plugged fuel return can also cause whitesmoke.

Some sources of white smoke directly relatedto improper burning of fuel are:

• Coolant in combustion chamber:- blown head gasket(s)- crack in block or cylinder head

• Fuel:- fuel contaminated (with gasoline)- condensation (water) in fuel

• Injection pump timing advanced• Light load advance piston stuck.• H.P.C.A.–housing pressure cold

advance inoperable.• Excessive white smoke on start-up:

- faulty glow plug(s) or glow plug circuit.

5


• Fuel leaks:- pump- lines- filters

• Injection pump timing• Stuck advance piston• Injector pump solenoid• Governor weight retainer ring• Improper fuel

- water in fuel- gasoline in fuel

G. ENGINE HARD STARTING (COLD)

• Battery/batteries condition andconnections (cables)

• Check charging/starting systems• Cranking speed (min. 150 RPM’s)

- excessive starter draw- oil viscosity (to heavy)

• Fuel contamination- improper type- water in fuel- gasoline in fuel

• Glow plug(s)- glow plug circuit – 1.5 to 5.0 ohms

• Amps 110 amps draw• Operator uses improper starting

procedure• Housing pressure cold advance - check

ball contacts• Injection pump timing - incorrect• Injection pump solenoid (at least 24 volts

to actuate)• Fuel line leak (filter leak) drawing air into

system• Advance piston (stuck)• Broken advance pin• Fuel-lift pump (low pressure)• Fuel leaks (major)

- injector lines- pump- injector(s) leaking down

D. BLUE SMOKE COMING FROMEXHAUST

Blue smoke indicates that engine oil is burningin the cylinder or cylinders and may beaccompanied by excessive oil consumption.

Some mechanical conditions which should beconsidered are:

• Stuck piston rings• Worn piston rings• Failed valve seals, worn valve stems

and/or guides• Faulty crankcase vent valve• Cylinder walls out of round

Some non-mechanical checks include:• Oil level too high (overfilled crankcase)• Fuel oil in crankcase• Improper oil viscosity (too thin)• Clogged CDR valve

E. DIESEL ENGINE KNOCK

Diesel engine knock may be caused by apiston. The piston knock sounds very similar tocombustion knock. To assist in the diagnosis,with the engine off, retard the injection pumptiming as far as the slot in the pump flange willallow. This will quiet down a combustion knock.If the knocking is not substantially reduced, thenoise is most likely a mechanical problem.Crack the fuel injection lines one by one toidentify the cylinder with the knock. The knocktone will change when the line is crackedfeeding the cylinder with the problem.

F. ENGINE HARD STARTING (HOT)

• Compression (min. 380 PSI) hot• Excessive starter draw when hot• Cranking speed hot• Leaking injector(s) nozzles:

- fuel in cylinder- air from cylinder in pump


Page 3-6

Figure 3-2. Fuel System Schematic.

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7


H. FUEL SYSTEM FLOW SCHEMATIC(Figure 3-2)

1. Inlet Pressure-1. Fuel Tank2. Fuel Tank Screen (Filter)3. Fuel Lines (Low Pressure)4. Fuel/Water Separator5. Mechanical Lift Pump6. Internal Filter7. Pressure Regulator Assembly

Fuel is drawn from the fuel supply tank (1),through the in-tank filter (2), and low-pressureline (3) by the mechanical fuel pump (4),mounted on the lower right-front side of theengine. The fuel is then pumped (4-7 psi),through a low-pressure supply line to the fuel/water separator (5) where water andcontaminants are filtered out. Clean fuel isthen pumped to the fuel injection pump internalfilter (6) mounted in the back of the fuel injectionpump and to the back side of the pressureregulator valve assembly (8). At each of thesepoints the fuel pressure should be between 4and 7 psi.

2. Transfer Pump Pressure-1. Transfer pump2. Pressure Regulator Valve3. Metering Valve4. Charging Passage

NOTE

Transfer pump output volume andpressure increase as pump speedincreases.

Fuel under transfer pump pressure (12-130psi), flows through the center of the transferpump rotor (7), past the rotor retainers into acircular groove on the rotor. It then flowsthrough a connecting internal passage in thehydraulic head (9) to the automatic advance

mechanism (20) and up through an internalpassage to the metering valve (11). Some fuelis bypassed through the pressure regulatorassembly (8) back to the low pressure (inlet)side.

The radial position of the metering valve (11),controlled by the governor linkage (25),regulates flow of the fuel into the radial chargingpassage which incorporates the head chargingpassages and ports (12). At each of thesepoints, fuel pressure should be between 12 and130 psi.

NOTE

As the pump speed increases, the transferpump

pressure increases causing the

automatic advance mechanism to rotatechanging pump timing.

At low speeds, because transfer pump pressureis comparatively low, the cam remains in theretarded position. When engine speedincreases, transfer pump pressure rises andmoves the piston in the advanced direction.Advance piston movement is related to enginespeed.

3. Housing Pressure Circuit:1. Vent wire Assembly2. Governor Housing3. Governor weights4. Governor Springs5. Automatic Advance Mechanism6. Advance Cam Ring

In addition, an air vent passage in thehydraulic head (9) connects the outlet side ofthe transfer pump with the pump housing. Thisallows air and some fuel to be bled back to thegovernor housing (27). This fuel fills the housing,lubricates internal components, cools the pumpand allows small air bubbles to be bled off to thefuel tank (1). A vent wire assembly (10) isinstalled in the governor housing radial passage.


Page 3-8

5. Fuel Return Circuit:1. Injection Pump Fuel Return Lines: (metal)

2Injector Nozzle Fuel Return Lines:(rubber)

3. Return Circuit Through Nozzle:

The purpose of the fuel return circuit is tomaintain a constant pressure within the pumpbody. It vents air from the charging circuit.Excess fuel, unburned fuel, and air bubblesin the fuel injection pump and nozzles isreturned to the fuel storage tank throughrubber and metal fuel return lines. Fuelinjector nozzles bleed back from nozzle tonozzle, to the tank.\

6. Fuel Shutoff Solenoid: 24 VDC:

The fuel shutoff solenoid (24) is fastened tothe inside of the governor housing cover andelectrically connected to the ignition switch.When the ignition switch is placed in the startor run position the fuel solenoid (24) isenergized pulling the linkage (25) forwardrotating the metering valve (11) to the run,(fuel-on) position allowing fuel to flow throughthe metering valve (11) to the rotor (13) andinjectors (18).When the fuel shutoff solenoid coil (24) is de-energized, the shutoff arm spring pivots thetop of the arm to the left, and the bottom ofthe arm to the right, thus forcing the linkagehook to move rearward and the meteringvalve (11) to rotate to the no-fuel position.If the solenoid (24) fails to operate andprevents a shutoff or run condition,disconnect the electrical wire # 54a at the fuelinjection pump and check for the presence ofbattery voltage. If battery voltage is presentcheck for a defective solenoid. If batteryvoltage is not present, troubleshoot electricalignition system.

The vent wire (10) spins freely breaking largeair bubbles into small ones. Fuel under governorhousing pressure flows through a radialpassage to the automatic advance mechanism(20) applying governor housing pressure tothe back side of the advance mechanism.The pump operates with the housingcompletely full of fuel; there are no dead airspaces anywhere within the pump.

4. Housing Pressure Cold Advance System:

This system consists of a housing pressurecold advance solenoid (23), a housingpressure regulator (22), and a housingpressure cold advance switch mounted onthe rear of the right head assembly.When the engine is cold, (below 90°F), thehousing pressure cold advance switch isclosed. With the switch closed, current flowsacross the switch to the housing pressurecold advance solenoid (23), activating andopening the housing pressure regulatorvalve (22).

The HPCA solenoid (23) is activated througha temperature switch located at the rear ofthe right cylinder head assembly. The HPCAsolenoid is located in the governor housingcover. For cold starts ,when engine coolanttemperature is low , (below 90°F), the solenoidplunger lifts the check ball off its seat. Thisreduces housing pressure to almost zero.With no housing pressure in the advancemechanism (20), the fuel at transferpressure can advance the cam ring (21),more easily when the engine is cranking.Injection timing is advanced about 3° toreduce white smoke and improve cold-idlesmoothness. Now that the engine is warmedup, it will run smoothly. The switch operatessimilar to an automatic choke onautomobiles.

9


I. TROUBLESHOOTING AND TESTING

NOTE

Now that you understand the principlesof operation you can use the schematicsto assist you in troubleshooting thediesel fuel injection pump.

a. Check pump advance operation bypushing the advance mechanism lever(28) in while the engine is running at anidle. A drastic change in engine RPM’swill occur if the advance system (20) isoperating properly.

b. Check fuel pressure at the fuel lift pump(4) outlet hose. The easiest point tocheck is at the inlet hose on the fuel/water separator (5). Pressure must bebetween 4 & 7 psi.

c. Check fuel filter/water separatorcondition. After checking lift pumppressure remove filter outlet hose andconnect a pressure gage. Start theengine. Outlet pressure should be thesame as lift pump pressure. If thepressure is lower, it is an indication offilter blockage.

d. Fuel Pump Advance Mechanism Check:Crimp the rubber fuel return line on topof the fuel injection pump cover. Theengine should shut-down. If enginecontinues to run, indication is that theautomatic advance timing mechanisminside the pump is malfunctioning.

J. ELECTRICAL FUEL SOLENOID

With the ignition switch in the run position,disconnect the fuel shutoff solenoid (24)electrical lead # 54a. Connect and disconnectthis wire several times. An audible clickingsound will be heard each time the solenoidactivates if it is good.

K. COLD ADVANCE SOLENOID TEST

With the ignition switch in the run position,Disconnect the #569a and #569b wires fromthe cold advance switch mounted on the rear ofthe right head assembly. Connect #569a and#569b wires together. If the housing pressurecold advance solenoid (23) and regulator (22)are good, an audible click will be heard.

L. CHECKING HOSING PRESSURECOLD ADVANCE SWITCH

To check the housing pressure cold advanceswitch, disconnect the #569a & 569b wiresfrom the switch located on the rear of the righthead assembly. Set an ohm meter to RX1.When the engine is cold, (below 75°F), therewill be continuity across the switch if the switchis good.

M. FUEL INJECTION PUMP TEST

If you have fuel at the fuel injection pump inletport and no fuel at the injectors, indication isthat the pump has internal malfunctions.


Page 3-10

N. UNDERSTANDING DIESEL FUEL

1. Diesel Fuel:

To understand how a diesel injection pumpoperates, a knowledge of diesel fuelcharacteristics is required. Diesel fuel can beblended to suit different kinds of diesel engines,just like different blends of gasoline for a spark-ignition engine. Three terms used to describediesel fuel are (1) viscosity, (2) cloud point, and(3) cetane rating.

2. Viscosity:

Diesel fuel has a higher viscosity than gasoline,that is, it's thicker or heavier. The followingsections show how the viscosity of diesel fuelcan affect combustion and injection pumpoperation. There are two grades of fuel ingeneral use, called No. 1 and No. 2. No. 1diesel fuel has a lower viscosity than No. 2 fuel,so it flows better at low temperatures. No. 2 fuelprovides more heat energy than No. 1, so adiesel engine operates a little more efficientlyon No. 2 fuel. (Heat energy is measured inBritish Thermal Units, or BTUs).

The choice of which fuel to use is usuallydetermined by the temperature in an area atany given time of year. The fuel characteristicsrelating to temperature are cloud point andpour point.

3. Cloud Point and Pour Point:

Diesel fuel contains paraffin wax. The paraffingives diesel fuel its heat energy. Cold temperaturescan cause the paraffin to separate and form waxcrystals. These crystals can eventually block thefuel filter. The cloud point of diesel fuel is thetemperature at which the wax starts to separate,and the fuel turns milky white, or cloudy. BecauseNo. 2 contains more paraffin than No.1, its cloudpoint is higher, around 20°F (–7°C). The cloudpoint of No.1 fuel is about –20°F (–29°C). Thetemperature at which the fuel stops flowing isknown as the pour point. To lower the cloud pointof the fuel and prevent fuel filter blockage, awinterized blend of No.1 and No. 2 fuels is sold incold climates. It is also possible to use an in-linefuel heater, located between the fuel pump andthe fuel filter. The heater is actuatedthermostatically at about 20°F (–7°C) and isdesigned to prevent wax crystal formation in thefuel filter.

4. Cetane:

A cetane rating for diesel fuel is similar to anoctane rating for gasoline. The cetane numberindicates how quickly ignition will take place whenthe fuel is injected into the cylinder. If the cetanenumber is too low, ignition is slow , and the enginemay knock and emit black smoke. But if thecetane number is too high, ignition may occur tooquickly and the fuel is not completely burned,again causing black smoke. You cannot alter thecetane rating of a particular fuel, but you shouldknow what symptoms can be caused by usingincorrect or poor quality fuel.

11


5. Diesel Combustion:

It's also helpful to understand the combustionprocess in a diesel engine, because it'scontrolled differently than in a gasoline engine.

A diesel engine does not use a throttle plate toregulate air flow to the engine, so enginespeed is controlled by the amount of fuelinjected. Injection is explained in detail in thesection on Injection Pump Operation. Sincethe amount of air is relatively constant, the air-fuel ratio of a diesel engine can be as low as100:1 at idle, rising to 20:1 at wide-open throttle.These ratios are leaner than in a gasolineengine and are one of the reasons for a dieselengine's higher fuel economy.

A diesel engine does not have an electricalignition system. The heat of the air compressedin the cylinder ignites the fuel injected into theengine. Diesel engine compression ratios areoften higher than 20:1, and the temperature ofthe compressed air may reach 1,000°F. Thefuel is injected at or just before the end of thecompression stroke, it mixes with the hot air,vaporizes, and ignition starts.

Ignition is not instantaneous everywhere in thecylinder. The fuel burns only where it has beenvaporized by the hot air, and this takes longerthan in a gasoline engine. This process iscalled controlled combustion. Two additionalreasons for the diesel engine's greaterefficiency are (1) the high compression ratio,and (2) the longer combustion period.

The viscosity of the fuel can affect combustion.If the fuel is too heavy (high viscosity), it doesnot vaporize properly in the cylinder. It's toorich to burn. If the fuel is too light (low viscosity),it may not be injected far enough into thecylinder to mix properly. Both conditions cancause poor combustion and result in loss ofengine power.

O. TYPICAL FUEL PROPERTIES(Figure 3-3)

• Pour point and cloud point determineminimum temperature engine canoperate with waxy type fuel.

• Diesel fuel pour point is temperaturewhere fuel stops flowing.

• Diesel fuel cloud point is temperature atwhich wax separates from fuel.

• The No.1 Diesel cloud point is about –20°F(-29°C).

• The No. 2 Diesel cloud point is about 20°F(-7°C).

GASOLINE

5.9

18,700

110,330

0,5

-40°

JP4

6.5

18,400

119,600

0.7

100°

#1 DIESEL

6.9

19,583

137,000

2.0

100°

#2 DIESEL

7.2

19,855

141,000

2.7

125°

LB/GAL

BTU/LB

BTU/GAL

FLASH POINT

VISCOSCITY,CENTISTOKES

PR

OP

ER

TIE

SFUEL

Figure 3-3. Typical Fuel Properties.

P. ENGINE CRANKING SPEED TEST

Using a tachometer, check engine crankingspeed. Ensure speed is 150 RPM minimum. Ifcranking speed is too low, check battery voltage.If battery voltage is OK, check for incorrectengine oil. Drain and refill with recommendedoil. If battery voltage is correct and correct oil isin the engine, check for starter dragging.

Q. FUEL PUMP PRESSURE TEST

Check pressure at fuel pump outlet; if pressureis not at least 4 psi (28 kPa), replace fuel pump.


Page 3-12

R. FUEL FILTER (Figure 3-15)

The following illustration depicts the fuel filteringcapabilities in the HMMWV.

Figure 3-15. Relative Size of Micron Particles

S . FUEL ECONOMY

On the highway, in the 50-75 M.P.H. range, thefuel economy will go down about 3 M.P.G. foreach 10 M.P.H. increase in speed. M.P.G. willincrease with the use of a steady foot, easyacceleration and light braking. Fuel economymay vary as much as 5 M.P.G. with differentdrivers.

T. FUEL FILTER PRESSURE TEST(Figure 3-4)

Check fuel supply pressure (1) using pressuregage. Pressure should be 4 psi (28kPa)minimum. If pressure is not at least 4 psi(28kPa), clean fuel filter (2) and repeat test. Ifpressure is still not at least 4 psi (28 kPa), checkfuel supply lines and hoses for restrictions andobvious damage. Replace any damaged linesor hoses. If lines and hoses are not damaged,check fuel pressure at lift pump outlet. Normalpressure is 4–8 psi (28–55 kPa).

Figure 3-4. Fuel Filter Pressure Test Hook-up.

13


U. FUEL FILTER FLOW TEST(Figure 3-4)

Disconnect fuel filter outlet hose (3) and routeinto quart capacity container. Crank engine for30 seconds. Container should be at least half-fullor contain 1 pint (0.51 liter). If volume is notsufficient, check fuel supply and return lines andhoses for restriction and obvious damage.Replace any damaged lines or hoses. If norestrictions or obvious damage is found, replacefuel pump.

V. FUEL TANK CONTAMINATION TEST

Drain fuel filter while cranking engine amaximum of 30 seconds. If water andcontamination is present, wait two minutesand repeat test twice. If water andcontamination is still present, drain and cleanfuel tank and refuel vehicle.

NOTE

Bubbles in fuel stream may indicate thepresence of air in the fuel system, andwhite exhaust smoke will be seen duringcranking.

W. FUEL INJECTION PUMP TEST(Figure 3-5)

If there is fuel at the fuel injector pump inlet lineand engine will not run, loosen fuel injectionlines (1) at injection nozzles and crank engine.If no fuel leaks from fuel injection lines whilecranking engine, replace fuel injection pump.

Figure 3-5. Fuel Injection Pump Test.


Page 3-14

WARNING

Use of any injector other than the one specified fora particular engine could cause serious damageto the engine and / or performance

15


X. FUEL INJECTOR NOZZLE TEST(TEST STAND) (Figure 3-6)

1. Testing Preparation:

a. Connect fuel injection nozzle (2) to tester.

b. Connect lines to return line nipples (1).

Figure 3-6. Fuel Injector Nozzle.

WARNING

Do not place hands or arms near nozzleduring testing. Penetrating force of oilmay cause serious injury or death.

c. Close shutoff valve to pressure gage ontester.

d. Operate tester to prime nozzle (2).

2. Obtaining pressure check:

a. Open shutoff valve to pressure gage 1/4turn.

b. Depress lever on tester slowly. Note at whatpressure the needle on pressure gage stops.Opening pressure must be between 1,500psi (10,343 kPa) and 1,960 psi (13,514 kPa).Replace nozzle (2) if opening pressure doesnot meet specifications.

3. Leak Test:

a. Open shutoff valve to pressure gage anadditional 1 turn.

WARNING

Compressed air used for cleaningpurpose will not exceed 30 psi (207 kPa).Use only with effective chip guardingand personal protective equipment(goggles/shield, gloves, etc.).

b. Blow-dry end of nozzle (2).

NOTE

1,400 psi (9,653 kPa) must be maintainedfor 10 seconds while checking for nozzleleakage.

c. Depress lever on tester until pressure gagereads 1,400 psi (9,653 kPa) and observetip of nozzle (2). If a droplet forms and dropsoff the nozzle (2) in 10 seconds or less,replace nozzle (2).

4. Chatter Test:

a. Close shutoff valve to pressure gage.

b. Depress lever on tester slowly, notingwhether a chattering noise can be heard.

NOTE

Faster lever movement may cause nozzleto hiss or squeal rather than chatter, thisis acceptable.

c. If no chatter is heard, increase speed oflever movement on tester until nozzle (2)chatters. If no chatter is heard, replacenozzle (2).


Page 3-16

One cause of blockage is the leak-off nipple onthe nozzle being plugged on the bottom end.During assembly of the nipple into the nozzlebody, the epoxy sealant may have flowed overthe hole in the nipple on the bottom end. If thishappens, the return flow of fuel is restricted.

To determine if the hose or nipple cap fall offwas caused by a blocked nozzle passage:

1. Remove the hoses from all nozzle nippleson the side of the engine involved.

2. Using a vacuum gage, attach it to onenipple on a nozzle. If the nozzle nipple endis plugged, a vacuum reading will result.Check each nozzle.

3. Nozzles that indicate a plugged or partiallyplugged opening will generate some readingon the vacuum scale.

4. To unplug a suspected plugged nipple,insert a small drill bit into the nozzlenipple and turn by hand to break theepoxy covering.

5. Recheck with vacuum. If unable to breakthe epoxy barrier, the nozzle should bereplaced.

6. Replace hoses and nipple.

Figure 3-10. Fuel Injection NozzleBlockage Check.

5. Spray Pattern:

a. Depress lever on tester quickly. Spraypattern must be cone-shaped with nostreamers. Replace nozzle if streamers inspray pattern are present.

b. Remove nozzle from tester.

Y. FUEL INJECTOR NOZZLE TEST(IN VEHICLE)

A quick check of the nozzle’s condition while itis still on the engine is performed as follows:

1. Run the engine until it is at operatingtemperature.

2. With the engine running at an idle RPM,loosen the fuel line nut at the nozzle (placea rag around it). The engine shoulddecrease in RPM (similar to shorting out aspark plug in a gasoline engine) if thenozzle is operating properly. If there is nochange in engine RPM, then the nozzle isnot operating correctly and should beremoved.

Z. 6.2L INJECTION NOZZLE RETURNHOSE (Figure 3-10)

Conditions may arise where the fuel returnhose or nipple cap is disconnected from thefuel injection nozzle.

The purpose of the fuel hose is to return thefuel which leaks past the pintle in the injectornozzle, back to the fuel tank. This is a relativelysmall amount of fuel. Starting with the endcylinders on each side of the engine, the fuelpasses through each succeeding nozzle. If ablockage occurs in this flow path, pressure willbuild up and result in a fuel leak at the cap orhose.

17


AA.FUEL SOLENOID TEST - ENGINECRANKS BUT WILL NOT START(Figure 3-7)

Check electrical connections at injection pump.Ensure lead 54A (1) is connected to fuelsolenoid terminal (front terminal) and 569B (2)is connected to cold advance solenoid terminal(rear terminal).

Check for power to fuel solenoid. Disconnectlead 54A (1 ) from fuel solenoid terminal. Usingmultimeter, check for voltage at lead 54A withrotary switch in “RUN” position. If voltage ispresent, but less than 17 volts, check batteries.If no voltage is present, disconnect enginewiring harness connector from protective controlbox and check for continuity between pin A inengine wiring harness connector and lead 54A.

1. If no continuity is present, repair enginewiring harness. Connect engine harnessconnector to protective control box.

2. If continuity is present, check for batteryvoltage (approximately 24 volts) at lead29C in body wiring harness connector, atprotective control box, with rotary switch in“RUN”. If battery voltage is present, replaceprotective control box. If no voltage ispresent, repair body wiring harness.

Check operation of fuel solenoid. Disconnectlead 54A from terminal on top of injectionpump. Turn rotary switch to “RUN”. Touch leadto fuel solenoid terminal and remove. An audibleclicking sound should be heard from within thepump each time contact is made.

Figure 3-7. Fuel Solenoid Test Hook-up.


Page 3-18

BB.COLD ADVANCE SOLENOID-SWITCH TEST (Figure 3-8)

Remove engine access cover. Disconnectleads 569A (1) and 569B (2) from cold advanceswitch (3). Using a multimeter, check for batteryvoltage at lead 569A with the rotary switch in“RUN” position and engine coolant below 85°F(29°C). If battery voltage is not present, repairengine wiring harness.

Disconnect lead 569B from fuel injection pump.Using a multimeter, check for continuity throughlead 569B at the fuel injection pump to lead569B at the cold advance switch. If continuityis not present, repair engine wiring harness.

Using a multimeter, check for continuity throughthe cold advance switch with enginetemperature below 85°F (29°C). If continuity isnot present, replace cold advance switch. Checkfor continuity through cold advance switch withengine temperature above 85°F (29°C). Ifcontinuity is present, replace cold advanceswitch. Connect lead 569B to injection pumpand leads 569B and 569A to cold advanceswitch.

NOTE

A bad switch will cause engine to runrough at idle speed until engine warmsup to operating temperature. It will alsoproduce white smoke at exhaust outlet.

Figure 3-8. Cold Advance Solenoid andSwitch Hook-up.

19


CC.INJECTION PUMP AIR PRESSURETEST

If leaking injection pump seals are suspected butthe location of the seal(s) is unknown, or ifinjection pump seals have been replaced, it is agood practice to pressure check the injectionpump before reinstalling it onto the engine.

Procedure:

1. If the pump has been removed for thepressure check or is already off of the engine,drain all diesel fuel from the pump.

CAUTION

Air will be used to pressure check thepump; therefore, it is imperative that shopair be routed through a filter before hookingit up to the injection pump. The air must beclean and moisture free (dry).

2. Connect an air line to the injection pumpinlet.

3. Seal off the injection pump return line fitting.

4. Immerse the injection pump assemblycompletely in a bath of clean test oil(preferably diesel calibrating fluid) that hasbeen heated to normal test temperature,usually between 110–115°F (43–46°C).

5. Allow the injection pump to sit in the test oilfor at least 10 minutes, then apply air pressureto the pump at a maximum of 20 psi(137.91kPa). Let the pump sit for another 10minutes to allow any trapped air to escape.

6. If no leaks are apparent after this time period,reduce the air pressure to 2 psi (13.8 kPa) for30 seconds. If no leaks exist, increase thepressure to 20 psi (137.9kPa) again. If noleaks are evident, the pump is satisfactory.

DD. INJECTOR LINE LENGTH

Fuel within the injection pump is routed througheach of the high-pressure injector lines in theengine firing order sequence to each cylindernozzle.

Although each injector line is a different shape,they are all the same length. Any differences inlength would cause a change in the injectiontiming. A longer line would retard the timing,while a shorter line will advance the timing.

EE.WATER IN INJECTOR PUMP

The presence of water in diesel fuel can bedisastrous. Water is a non-compressible liquid,and if forced through a injector, can actuallyblow the tip off of the injector nozzle. In addition,water will corrode internal injection systemcomponents if left in the system. One functionof diesel fuel is to cool and lubricate the internaloperating components of the injection pump.Most diesel fuels used in high-speed automotiveapplications have a viscosity rating of between33 to 40 SSU (Saybolt Seconds Universal) at100°F (37.7°C). The presence of water greatlyreduces the lubricating ability of the fuel resultingin little or no lubrication between the movingparts. Seizure can result.


Page 3-20

Figure 3-9. Electrical Shutoff Solenoid.

"NO FUEL" POSITION(DE-ENERGIZED)

METERING VALVE(ROTATES TO

STOP FUEL FLOW)RUNNING POSITION

(ENERGIZED)

ELECTRICSHUTOFFSOLENOID

PLUNGER

ARM

FF. FUEL RETURN VALVE TEST

Procedure:

1. Connect a rubber hose and fitting to fuelreturn valve outlet on pump top cover.

2. Connect a 24 volt lead to cold start advancesolenoid connector on pump top cover.

3. Blow through the rubber hose. If there is norestriction, the fuel return valve issatisfactory.

GG.FUEL SHUTOFF SOLENOID TEST(Figure 3-9)

Connect a 24 volt lead to fuel shutoff solenoidconnector on pump top cover and remove.Repeat this step two or three times. Each timethe lead is removed an audible clicking soundshould be heard from within the cover and thearm on the solenoid should move.

21


HH. DIESEL FUEL QUALITY(Figure 3-12)

The diesel fuel hydrometer J-34352 can beused to measure specific gravity of fuel. Whentesting fuel, fuel temperature should be 60°Ffor best accuracy. Fuel specific gravity is anindication of the Cetane Number, and thus, thequality of a fuel. A poor quality fuel can impairdiesel engine performance. The followingprocedure outline how to measure diesel fuelquality.

NOTE

The glass hydrometer, including floatportion, is very delicate. Extreme caremust be taken when using this tool.

1. Fill a clean quart jar 3/4 full of diesel fuel.2. Fill the glass hydrometer container with fuel

until the hydrometer floats.3. Gently spin the tool to break the surface

tension.4. Read scale where the fuel level contacts

the hydrometer float.5. Scale code:

Green = High quality fuel*Yellow = Medium quality fuelRed = Possible low quality fuel

NOTE

The yellow band above the green band indicatesa possible gasoline diesel fuel mixture.

Yellow(mix fuel)

Yellow(medium)

Green(High)

Red(low)

Diesel Fuel Quality Tester.


Page 3-22

4. Gasoline will not harm the injection system.Flush the gasoline out of the system asoutlined. Do not remove any injectionequipment unless engine operation isunsatisfactory after the system has beenflushed.

5. For water, remove the engine fuel filterand inspect the contents for thepresence of water. If water is found,remove the injection pump cover. If thepump is full of water, flush system.

6. Small quantities of surface rust in theinjection pump will not create a problem. Ifthe vehicle stalls as a result ofcontamination, remove the meteringvalve and polish it lightly with 600 gritpaper to remove the contaminant. If theadvance piston is stuck as evident by poorperformance, smoke or noise, it may benecessary to remove the pump to free it up.

7. Occasionally contamination may enter thesystem that becomes so severe thatphysical damage has occurred to thesprings and linkage in the pump.

8. These pumps must be replaced.

JJ. DIESEL FUEL CONTAMINATION

Various malfunctions in diesel engines oftenlead to injection pump replacement. Beforereplacing the injection pump, determine if wateror an excessive amount of gasoline is thecause of the malfunction. If water or gasoline isfound to be the cause of the malfunction,injection pump and injection nozzle replacementmay be necessary. The following procedureshould help to eliminate unnecessary pumpand nozzle replacement in the event of fuelcontamination.

1. Remove the engine fuel filter and inspectthe contents for the presence of water orgasoline. If water or gasoline is found, flushthe system.

2. Fuel contamination should be expectedif the vehicle stalls, performance is pooror in the case of gasoline, the enginewill knock loudly.

3. If gasoline is suspected, remove the fuel fillcap and check for the presence of gasolinefumes.

23


KK. DIESEL FUEL SYSTEM CLEANINGPROCEDURE

NOTE

You should remove the fuel tank forcleaning when water is detected, becauseof the current understanding that a smallamount of water is potentially damagingto the fuel system. Remove all of it.

CAUTION

Never drain of store diesel fuel in anopen container due to possibility of fire,explosion, or contamination.

1. Drain the fuel tank.

2. Remove the tank gage unit.

3. Thoroughly clean the fuel tank. If the tankis rusted internally, it should be replaced.Clean or replace the fuel pickup filter andcheck valve assembly.

4. Reinstall the fuel tank but leave the linesdisconnected at fuel tank area (above therear axle).

5. Disconnect the main fuel hose at the fuelpump. Using low air pressure, blow out linetowards rear of vehicle. Disconnect thereturn fuel line at the injector pump, withlow air pressure, blow out the line towardsthe rear of the vehicle. NOTE: IF RUSTIS PRESENT IN PIPES, THEY MUST BEREPLACED.

6. Reconnect the main fuel and return linehoses at the tank. Fill the tank at least 1/4 full with clean diesel fuel. Reinstall fueltank cap.

7. Remove and discard the fuel filter.

8. Connect the fuel hose to the fuel pump.

9. Reconnect battery cable.

10. Purge the fuel pump and pump to filter lineby cranking the engine until clean fuel ispumped out, catching the fuel in a closedmetal container.

11. Install a new fuel filter.

12. Install a hose from the fuel return line (fromthe injection pump) to a closed metalcontainer with a capacity of at least twogallons.

13. If the engine temperature is above 125°F(52°C), activate the injection Pump HousingPressure Cold Advance (H.P.C.A.). Thiscan be done by disconnecting the two leadconnectors at the engine temperature switch(located at the rear of the right cylinderhead), and bridging the connector with ajumper.

14. Crank the engine until clean fuel appears atthe return line. Do not crank the engine formore than 30 seconds at one time. Repeatcranking if necessary with 3 minute intervalsbetween crankings.

15. Remove the jumper from the enginetemperature switch connector andreconnect the connector to the switch.

16. Crack open each high pressure line at thenozzles using two wrenches to preventnozzle damage.

17. Disconnect the lead to the H.P.C.A. solenoid(on the injection pump).

18. Crank the engine until clean fuel appears ateach nozzle. Do not crank for more than 30seconds at one time. Repeat cranking ifnecessary, with 3 minute intervals betweencrankings.


Page 3-24

LL. CLEANING PROCEDURE:GASOLINE IN FUEL SYSTEM

1. Drain fuel tank and fill with diesel fuel.

2. Remove fuel line between fuel filter andinjection pump.

3. Connect a short pipe and hose to the fuelfilter outlet and run it to a closed metalcontainer.

4. Crank the engine to purge gasoline out ofthe fuel pump and fuel filter. Do not crankengine more than 30 seconds with threeminutes between cranking intervals.

5. Remove the short pipe and hose and installfuel line between fuel filter and injectionpump.

6. Attempt to start engine. If it does not start,purge the injection pump.

7. Crack injector lines.

8. Purge the injection pump and lines bycranking the engine with accelerator heldto the floor, crank until the gasoline ispurged and clear diesel fuel leaks out ofthe fittings. Tighten fittings. Limit crankingto 30 seconds with three minutes betweencranking intervals.

9. Start engine and run at idle for 15 minutes.

NOTE

If gasoline is inadvertently pumped intothe tank, there will be no damage to thefuel system or the engine. The enginewill not run on gasoline. Gasoline has afeature called octane which defined isthe ability of the fuel to resist ignitionunder high temperatures. Gasoline is afuel that has high octane and it resists

ignition under high heat. It will only igniteby a spark. Gasoline in the fuel at smallpercentages, (0–30%), will not benoticeable to the driver. At greaterpercentages, the engine noise willbecome louder. Gasoline at anypercentage will make the engine hard tostart when hot. In the summer time, thiscould be a cause of a hot start problem.

MM. FUEL FLOW TEST (Figure 3-13)

1. Disconnect fuel line at the filter inlet.

2. Disconnect #54 wire at the fuel injectionpump electric shut-off solenoid. Place asuitable container at end of pipe and crankengine a few revolutions. If little or no fuelflows from open end of pipe, then fuel pipeis clogged or pump is inoperative.

3. If fuel flows in a good volume from pipeat filter (1 pint in 30–45 seconds), fueldelivery pressure may be checked. Thistest is necessary because a weak pumpcan still produce an adequate volume offuel when it is not under pressure. Fuelpressure should be in the 4 to 8 psirange.

Figure 3-13. Fuel Flow Test.

25


NN. VACUUM TEST.FUEL LIFT PUMP INLET(Figure 3-14)

Low vacuum or complete loss of vacuumprovides insufficient fuel to the injection pumpto operate the engine throughout normal speedrange. The vacuum test will determine if thepump has the ability to pump fuel and is thebest indication of the quality performance ofthe pump.

Figure 3-14. Vacuum Gauge.

1. Disconnect hose from fuel tank to fuelpump at fuel pump. Plug or position hose toprevent fuel leakage.

2. Connect a vacuum gage to the fuel pumpinlet and attach a vacuum gage to thepump inlet.

3. Disconnect #54A wire at the fuel injectionpump electric shut-off solenoid, so that theengine will not start. Crank the engine untilyou obtain a reading in the vacuum gage.If vacuum is less than 12 inches Hg (2.98kPa) replace fuel pump.

OO. MECHANICAL FUEL PUMP TESTS

NOTE

Perform the following tests or inspectionsbefore removing pump.

Preliminary Inspection:

1. Check fittings and connections to insuretightness. If insufficiently tight, leaks of airand/or fuel may occur.

2. Check for fuel line bends or kinks in hoses.

3. With engine idling look for:

• Leaks at pressure (outlet) side of thepump.

• A leak on suction (inlet) side will reducethe volume of fuel on the pressure side ofthe pump and suck in air.

• Also check for leaks at diaphragm, flange,and at breather holes in pump casting.

• Check fuel pump steel cover and itsfittings for leaks. Tighten or replace fittingsas necessary. If fuel pump leaks(diaphragm, flange, steel cover, or pumpcasting breathing holes), replace pump.


Page 3-26

1

Section 4. Engine

SECTION 4ENGINE

NOTE

The compression ratio of this engine is21.5:1.

CAUTION

Due to the high compression ratio of thisengine and the use of glow plugs, do notat any time attempt to use starting fluidsto start the engine in cold weather. Theuse of such highly volatile liquids (ether)can result in serious engine damage dueto the explosive nature of this fluid withinthe cylinder as the piston is coming upon its compression stroke. This conditioncreates extremely high pressures thatattempt to oppose the piston’s upwardmovement. If the glow plugs are in theheated position and ether is sprayed intothe engine, this can cause severeexplosions within the cylinder and glowplug damage. In addition, ether tends toact as a drying agent and will cause lackof upper cylinder lubricant, which canalso cause engine damage.

Figure 4-1. Pre-combustion Chamber and Piston Crown Shape.

A. GENERAL ENGINE DATA(Figure 4-1)

The 6.2 liter diesel is designed, engineered,tested and manufactured specifically as a truckengine for tough, light-duty truck applications.

The 6.2 liter is a V-8 with a 90-degreeconfiguration. It is a four-cycle operation engineand naturally aspirated (not requiring a turbofor air induction). Its oversquare design, thebore being larger than the stroke, assists inreducing engine friction.

As with all IDI-type engines, this unit alsoemploys a glow plug in each cylinder to facilitateengine starting. Both the glow plugs and theinjectors are threaded into the cylinder headwith the injector nozzles being spring loadedand calibrated to open at a specified psi of fuelpressure.


Page 4-2

B. MANOMETER - BLOW-BY TEST

1. Run the engine at idle. Record waterpressure. The crankcase pressure at idleshould indicate zero inches of water or aslight vacuum.

2. Increase engine RPM to 2,000 RPM andrecord water pressure. The crankcasepressure at 2,000 RPM should be between1/2 inch and 4 inches of water vacuum.

NOTE

If water travel is one inch, you must addone inch for travel at other end ofmanometer scale.

C. GLOW PLUG TIP REMOVAL (DAM-AGED OR BROKEN) (Figure 4-2)

1. Remove fuel injector nozzle.

2. Using socket wrench and breaker bar ontorsion damper bolt, rotate crankshaftclockwise to bring piston (in affectedcylinder) to top dead center (TDC) positionto ensure intake and exhaust valves areclosed.

WARNING

Compressed air used for cleaningpurposes may exceed 100 psi (688 kPa).Use only with effective chip guardingand personnel protective equipment(goggles, shield, gloves, etc.).

3. Direct compressed air into glow plug port(1) to expel broken tip from prechamberthrough injector nozzle opening (2).

NOTE

In some cases it may be necessary toremove cylinder head to removeexpanded glow plug tip.

Figure 4-2. Damaged Glow Plug Removal

3

Section 4. Engine

D. ENGINE INJECTION PUMP TIMINGPROCEDURES USING KENT-MOORE TACH-N-TIME METER(Figures 4-3 through 4-7)

NOTE

Magnetic pickup receptacle (8) on timingbracket (1) must be correctly positionedor timing meter will not register correctly.

1. Insert timing bracket gauge into magneticpickup receptacle (8) on timing bracket(1).

2. Rotate timing bracket gauge so pointeron gauge fits into TDC notch (9) in timingbracket (1).

3. If pointer on gauge does not fit exactly intoTDC notch (9), bend magnetic pickupreceptacle (8) until pointer on timing bracketgauge fits exactly into TDC notch (9).

4. Remove timing bracket gauge from pick-up receptacle (8) on timing bracket (1).

NOTE

End of magnetic pickup (7) must be 1/16in. (1.6 mm) from torsional dampener.

5. Install magnetic pickup (7) into magneticpickup receptacle (8) and connect pickuplead (6) to timing meter.

NOTE

Clamp-on pickup (4) must be used on astraight section of tube no further than 4in. (10 cm) from injection nozzle.

6. Clean cylinder number one injection line (2)with metallic wool.

CAUTION

Do not overtighten clamp-on pickup ordamage to pickup will result.

7. Install pickup (4) on injection line (2).

8. Connect ground clip (3) to fuel injection line(2) and connect pickup lead (5) to timingmeter.

Figure 4-3. Engine Injection Pump Timing Meter Hook-up.


Page 4-4

a. Connecting Power Leads(Figure 4-4)

9. Route power leads of timing meter intobattery compartment and connect redpower lead (11) to rear battery + (plus)terminal (12).

10. Connect black ground lead (10) to negativebattery terminal (13). Display should lightup and read: SE-120.0.

Figure 4-4. Timing Meter Power Hook-up

NOTE

On 24 volt systems, do not connect theTach-N-Time to each battery. Powershould be derived from the positive andnegative terminals on the 12 volt systemsource (one battery).

5

Section 4. Engine

b. Enter Offset Chart (Figure 4-5)

1. Cylinder Number in the Firing Order – Thenumbers 1 thru 8 do not correspond to thecylinder numbers on the engine. Theyrepresent the cylinder numbers in firingorder. For example: When the enginesfiring order is 1-8-7-2-6-5-4-3, “1” refers tocyl. #1 (the first cylinder in the firing order),

“2” refers to cyl. #8 (the second cylinder inthe firing order), “3” refers to cyl. #7 (thethird cylinder in the firing order), etc.

2. Offset Entries – The offset entries are listedin crankshaft degrees, and correspond tothe position of the magnetic pick-upreceptacle in relation to TDC for theindividual cylinders.

Figure 4-5. Enter Offset Chart.


Page 4-6

c. Injection Pump TimingAdjustment TACH-N-TIME(Figure 4-6)

WARNING

Never adjust injection pump timing withengine running or injury to personnel ordamage to equipment may result.

1. Loosen three nuts (1) securing injectionpump (2) to timing cover (3).

NOTE

Moving injection pump 1/32 inch (1 mm)is equal to approximately 1 ° of injectionpump timing.

2. Move injection pump (2) clockwise to retardtiming or counterclockwise to advancetiming.

3. Tighten three nuts (1) securing injectionpump (2) to timing gear cover (3) andrecheck timing.

WITH #1 PISTON AT TOP DEAD CENTER (TDC)AS DETERMINED BY BALANCING THE POSITION OF#3 PISTON AND #6 PISTON, "0" REF LINE OF POINTER MUST ALIGN WITH CENTER OF TIMING.

NOTCH ON TORSIONAL DAMPERWITHIN ± 0.5 DEGREES.

72° 30'

9° 30' (6.2L)

CENTER OF TIMING NOTCH

FRONT

LC OF ENGINE

TIMING MARKS

RETARD

ADVANCE

MOVING INJECTOR PUMP1/32" (1 mm) EQUALS ANAPPROXIMATE 1° TIMINGCHANGE

NOTE:STATIC

TIMING MARKS

Figure 4-6. Timing Adjustment.

7

Section 4. Engine

d. Engine Injection Pump Timing(Figure 4-7)

CAUTION

Make sure all cables and wires are clearfrom fan, belts, and exhaust manifoldsbefore starting engine, or damage toequipment will result.

NOTE

If sensor light is not blinking, checkclamp-on pickup on fuel injection linefor proper installation.

1. Depress offset adjustment switch (3) andhold.

2. Operate increase/decrease switch (2) untiloffset adjustment reads 9.5 on display (4)and release offset adjustment switch (3).Display (4) should now read: 0000...0.0.

3. Start engine and warm up to operatingtemperature.

4. Position sensor switches (1) to clamp-onand magnetic pickup position.

5. Raise engine speed to 1300 RPM and readinjection pump timing on display (4). Timingmust be 4 before top dead center. If timingis not 4 before top dead center, stop engineand adjust timing.

6. Disconnect timing meter.

Figure 4-7. Timing with Dynamic Timing Meter.


Page 4-8

E. ENGINE INJECTION PUMP TIMINGPROCEDURES USING SNAP-ONLUMY/MAG II TIMINGMETER 12-VOLT DC (Figure 4-8)

1. Power Leads . These leads have color-coded clip boots. Red lead is connected topositive (+) terminal of 12 volt battery, andblack to negative (-) terminal or a goodvehicle ground.

2. Magnetic Pick-up Lead . This lead featuresthe male half of a “quick disconnect”coupling which attaches to either of the twomagnetic pick-up assemblies included withthe MT1480.

3. Magnetic Pick-ups . The MT88A pick-up,with convenient handle and flexibleextension, is designed for general use,while the MT89 is intended for use onvehicles with restricted access to themagnetic pick-up receptacle. Magneticpick-ups are used with both diesel andgasoline engines equipped with compatiblepick-up receptacles. The magnetic pick-up senses a groove or protrusion on aharmonic balancer, and provides precisecrankshaft or piston position and RPMdata to the meter. Magnetic pick-ups arecarefully calibrated to detect proper groovesor protrusions and to reject minor surfaceimperfections that may cause impropermeter readings. However, if an improperRPM reading occurs, use the optical orinductive pick-up to obtain the proper RPMreading.

4. Optical Pick-up Lead . The optical pick-upis connected to this lead at the lockingcoupling. The optical pick-up is used whenworking on diesel engines. The pick-upmonitors the start of combustion within anengine cylinder.

5. Luminosity Probe . The luminosity probeis installed in a diesel engine glow plughole. The probe has a quartz core whichserves as a “window” to the cylinder. Lightpulses, caused by combustion in thecylinder, pass through the “window” andare detected by the optical pick-up.

6. Optical Pick-up . The optical pick-upconnects to the luminosity probe. A photodetector inside the pick-up senses lightpulses that pass through the probe andchanges the light pulses to electrical signals.

7. RPM LED Display . The MT1480 has anRPM range of 40 to 8000 RPM and displaysin increments of 10 RPM. Just one pick-upconnection is required if only an RPMreading is desired. For a diesel engineRPM reading, either the magnetic or opticalpick-up can be used.

Diesel engine “cranking RPM” tests areperformed using the magnetic pick-up. Foruser convenience, the RPM display willhold the “cranking RPM” reading for aboutfive seconds after cranking is stopped.

8. Degrees LED Display . The MT1480displays engine timing to within 99° (inincrements of .5°) of engine offset settingsof 0° to 359.5°. This allows timing to beperformed from any engine cylinder.

The luminosity probe, optical pick-up andmagnetic pick-up are used for diesel enginetiming.

9

Section 4. Engine

9. Control Panel . The MT1480 features atouch control panel with ten digits (0–9), adecimal point (.) and two function controls- ENTER OFFSET and CHECK OFFSET.

The ten digits, decimal point, and enteroffset controls are used to enter thedesired degrees of offset. Offsets of .5°–359.5° may be entered in .5° (1/2°)increments, such as 1, 1.5, 2, 2.5, etc.This is termed a “valid” offset. Offsetsentered that are greater than 359.5 ornot in .5 increments are “invalid” and willbe rejected by the meter.

CHECK OFFSET is used to verify the degree ofoffset entered. The degrees entered aredisplayed by touching CHECK OFFSET.

a. Accessories Includedwith the MT-1480

MT95 Timing Bracket Gauge — The MT95 isused to check and align the position ofHUMMER 6.2L diesel engine magnetic pick-up receptacles. Instructions are packagedwith the MT95.

Figure 4-8. Snap-on Lumy/Mag II.


Page 4-10

b. Display Codes

The RPM and DEGREES displays providevaluable meter operation information in additionto RPM and timing readouts. An understandingof the following display codes is necessary forefficient use of the MT 1480.

“E” will appear when power leads are connectedto the battery. It indicates that the meter iswaiting for an offset to be entered.

If anything other than the “E” is displayed,press ENTER OFFSET to display the “E”.

“1480 READY” will move across the displaysafter a valid offset is entered. It indicates thatthe meter is ready, but no signals are going tothe meter. In other words, the engine has notbeen started and/or the pick-ups have notbeen connected.

“SNAP-ON” also indicates that the meter isready and no signals are going to the meter. Itwill appear after a valid offset is entered if pick-up leads are disconnected and/or engine isshut off.

Cranking RPM tests can not be performed ifthe displays read “SNAP-ON”. A valid offsetmust be reentered first.

“OFFS. Err.” (offset error) will be displayed if aninvalid offset is entered. If this occurs, pressENTER OFFSET and reenter a valid offset.“OFFS. Err.” indicates one of the followingerrors has occurred:

1. An offset greater than 359.5° was entered.

2. An offset using a decimal point not followedby a “O” or “5” was entered. Offsets must beentered as whole numbers or in incrementsof .5° (1/2°).

3. No offset was entered.

4. An offset with more than one number to theright of the decimal point was entered, suchas 9.50 or 9.05.

5. A four digit offset was entered, such as0100, or 0200.

6. An offset was entered using the decimalpoint but no number was entered after thedecimal point.

Displays show RPM reading, but no timingreading. It indicates that only one pick-up isconnected. Only one pick-up connection isrequired to monitor RPM on a diesel engine.Two pick-up connections are necessary tomonitor engine timing. The optical and magneticpick-ups are required for diesel engines.

11

Section 4. Engine

When timing an engine and only an RPM readingis displayed, check for the following potentialproblems:

1. No magnetic pick-up signal — Check bydisconnecting optical pick-up (diesel engine).If RPM reading is still displayed the magneticpick-up is functioning properly.

2. No optical pick-up signal — Check bydisconnecting the magnetic pick-up. If RPMreading is still displayed the meter is receivinga signal from the optical or inductive pick-upand the pick-up is working properly.

If the optical pick-up is connected, and noRPM reading is displayed when the magneticpick-up is disconnected, the problem maybe a dirty luminosity probe and not a badconnection or faulty pick-up.

3. Timing of engine is not within ±99° of offsetentered — Verify that the offset entered iscorrect for the engine and engine cylinderbeing tested. Press CHECK OFFSET andmake sure the correct offset degree wasentered.

4. RPM is too low — If the RPM reading is lessthan 400, no timing degrees will be displayed.

If anything other than a tach reading, timingreading, or one of the display codes mentionedappears, press ENTER OFFSET or disconnectand reconnect a battery power lead.

c. Operator Tips

Familiarize yourself with the following OperatorTips before doing any testing with the LUMY-MAG II. Tips are divided into two sections —Equipment Tips and Testing Tips.

d. Equipment Tips

1. When installing a luminosity probe in a glowplug hole, take care not to overtighten it.Follow torque specifications in testingsections.

2. Handle the luminosity probe with care.Dropping it may fracture the quartz. Do notuse a damaged probe.

3. Use a wet toothpick or wooden matchstick toremove carbon buildup from a luminosityprobe. Also, an ultrasonic cleaning unit, witha solution used for cleaning injector nozzles,will help to loosen deposits. Do not place hotprobe in liquid.

4. Sooty, dirty or broken probes will result inretarded readings. The luminosity probe willsoot up very fast when used in a cold engine.

5. Use a dry cotton swab to clean the lens in anoptical pick-up. Do not use solvent or anultrasonic cleaner.

6. Clean any spills, such as gasoline, brakefluid, cleaning solvents, etc. from the meter’sexterior immediately to protect the finish.

7. When not in use, the inductive pick-up shouldbe stored in the open position. This will helpto protect it if it is dropped.

8. Periodically check external lead connectionsto make sure they are secure.

9. For convenience, keep the enclosed quickreference ENTER OFFSET CHART near themeter.

10. The MT1480 is a highly sensitive and versatiletest instrument. Yet, if handled with care itshould provide years of dependable trouble-free service.


Page 4-12

e. Checking Cranking Speed

Cranking speed is extremely critical for a dieselto start, either hot or cold. Some tachometersare not accurate at cranking speed. An alternatemethod of checking cranking speed ordetermining the accuracy of a tachometer is toperform the following procedure:

1. Install a compression gauge into any cylinder.

2. Disconnect the injection pump fuel shut offsolenoid lead on the top of the injectionpump or at the harness connector.

3. Install the digital tachometer to be checked.

4. Depress the pressure release valve onthe compression gauge.

5. With the aid of an assistant, crank theengine for 2 or 3 seconds to allow thestarter to reach full speed, then withoutstopping, count the number of “puffs” atthe compression gauge that occur in thenext 10 seconds. Multiply the number of“puffs” in the 10 second period by 12 andthe resulting number will be the crankingspeed in revolutions per minute (RPM).

f. Hookkup Procedures andTesting Tips (Figure 4-9)

1. Engine must be in good running orderbefore timing adjustments can be donecorrectly.

2. Test engine must be at normal operatingtemperature for accurate test results.

3. Make sure that manufacturer’s preliminarytest procedures are followed to ensureaccurate test results.

4. When test readings are first displayed,allow a few seconds for display readings tostabilize.

5. Clean any dirt from the engine probe holderand crankshaft balancer rim.

6. A cylinder misfire can cause a momentaryincrease in the timing reading. If this occurs,allow the meter reading to stabilize.

7. If magnetic pick-up signal is lost when youlet go of an inserted magnetic pick-up, itmay be due to a spring-like return of themagnetic pick-up receptacle caused by atoo snug fit. A spray lubricant applied to thepick-up or receptacle may solve thisproblem.

13

Section 4. Engine

Figure 4-9. Hookup

g. Diesel Engine Timing

1. Place transmission selector in neutral,apply parking brake and block the drivewheels.

2. Clean timing marks located on pump flange,if needed, and check the position of themarks.


Page 4-14

h. Injection Pump Timing AdjustmentLUMY/MAG II (Figure 4-10)

WARNING

Never adjust injection pump timing withengine running or injury to personnel ordamage to equipment may result.

1. Loosen three nuts (1) securing injectionpump (2) to timing cover (3).

WITH #1 PISTON AT TOP DEAD CENTER (TDC)AS DETERMINED BY BALANCING THE POSITION OF#3 PISTON AND #6 PISTON, "0" REF LINE OF POINTER MUST ALIGN WITH CENTER OF TIMING.

NOTCH ON TORSIONAL DAMPERWITHIN ± 0.5 DEGREES.

72° 30'

9° 30' (6.2L)

CENTER OF TIMING NOTCH

FRONT

LC OF ENGINE

TIMING MARKS

RETARD

ADVANCE

MOVING INJECTOR PUMP1/32" (1 mm) EQUALS ANAPPROXIMATE 1° TIMINGCHANGE

NOTE:STATIC

TIMING MARKS

NOTE

Moving injection pump 1/32 inch (1 mm)is equal to approximately 1 ° of injectionpump timing.

2. Move injection pump (2) clockwise to retardtiming or counterclockwise to advancetiming.

3. Tighten three nuts (1) securing injectionpump (2) to timing gear cover (3) andrecheck timing.

Figure 4-10. Timing Adjustment.

15

Section 4. Engine

NOTE

Normally the alignment of the marks willbe quite close. If they are not, a variationin timing from the manufacturer’sspecifications can be expected.

3. Clean the magnetic pick-up receptacleand the harmonic balancer or flywheel asrequired.

4. Start the engine and allow it to idle untilit reaches normal operating temperature.Shut off the engine.

NOTE

Failure to fully warm the engine mayresult in erroneous readings andimproper pump adjustment. Combustiontiming will vary until the temperaturestabilizes.

5. Select cylinder to be used for testing.

NOTE

Select the correct offset to be enteredfor cylinder selected.

6. Clean dirt from around the glow plug ofcylinder selected.

7. Remove glow plug.

NOTE

If a carbon buildup around the glow plugheater element causes difficulty inremoving the glow plug, remove thebuildup. This will help to keep theluminosity probe’s “window” clean.

8. Install proper luminosity probe in glow plughole and torque to 8–9 lb ft (10–12 N•m).

CAUTION

Do not overtighten luminosity probe. Donot install a luminosity probe in an engineit is not specified for use on, as it mayresult in insufficient thread engagement.

9. Insert magnetic pick-up into pick-upreceptacle, making sure it is in far enoughto make contact with harmonic balancer,flywheel or crankshaft pulley.

If the pickup will be monitoring a protrusion,rotate the engine slowly and position theprotrusion in line with the pick-up receptaclehole. Insert the pick-up until it contacts thetop of the protrusion, and then back it outslightly.

10. Connect MT1480 power leads to battery(12 volts DC); red to positive (+) and blackto negative (–). “E” should be displayed onRPM display. If not, press “ENTEROFFSET” switch until “E” appears.

11. Enter the proper offset for the cylinder usedfor testing.

12. Start engine and adjust RPM tomanufacturer’s specification 650 RPM±25. Make sure that lead wires are clearof all moving or hot engine parts.

13. Observe light pulses for steadiness throughluminosity probe window. If pulses aresteady, continue testing. Irregular pulsesindicate a malfunction that must becorrected before timing adjustments canbe properly made.

14. Connect optical pick-up to luminosity probe.


Page 4-16

15. After engine has run several minutes at thespecified RPM, observe the timing reading.Recheck timing reading at two minuteintervals until reading stabilizes. Thisusually takes 4–6 minutes. Do not accepta reading that does not repeat at twominute intervals.

Timing must be 3° ±2° after top deadcenter at 1300–1400 RPM.

16. Shut off the engine.

A.If timing is within specifications, go tostep 22.

B.If timing is not within specifications, go tostep 17.

17. Loosen fuel injection pump bolts (orretaining nuts) to allow the pump to berotated.

18. Rotate the pump to advance or retard thetiming as needed. See page 4-6.

19. Retorque the pump bolts.

20. Start the engine and recheck the timing.

21. Repeat steps 15 to 20 until timing is tospecifications.

If the timing marks are far apart afterresetting the timing and the engine still hasa problem, the dynamic timing could still beincorrect because of a malfunctioningcylinder. When this occurs, check timingfrom any other cylinder. If there is still adifference in timing between cylinders, tryaveraging the timing by adding the timingreadings and dividing by the number ofcylinders checked.

22. Reset the idle to specifications and shut offthe engine.

23. Remove the meter and its attachmentsfrom the vehicle.

24. Replace and retorque the glow plug.Connect wire.

i. Cranking RPM Test (Min. 180 RPM)

1. Place the transmission selector in neutral,apply parking brake and block drive wheels.

2. Disable the engine to prevent it from starting.Disconnect the fuel shut-off solenoid wire(#54).

3. Connect MT1480 power leads to battery(12 volt DC); first red to positive (+) and theblack to negative (-). “E” should be displayedon RPM display. If not, press “ENTEROFFSET” until “E” appears.

4. Insert the magnetic pick-up into the pick-upreceptacle until it contacts the surface ofthe harmonic balancer, flywheel or pulley.

5. Enter any valid offset and press “ENTEROFFSET”. “1480 ready” should now moveacross the displays.

NOTE

If the display is blank or anything otherthan “1480 ready” is displayed,disconnect leads at battery and thenrepeat steps 3 thru 5.

6. Crank engine and monitor RPM. Themeter will hold the RPM reading for aboutfive seconds after cranking is stopped.(Min. 180 RPM).

17

Section 4. Engine

j. Enter Offset Chart (Figure 4-11)

Using the ENTER OFFSET CHART:

1. CYLINDER NUMBER IN THE FIRINGORDER - The numbers 1 through 8 do notcorrespond to the cylinder numbers on theengine. They represent the cylinder numberin the firing order. Example: if the engine’sfiring order is 1-8-7-2-6-5-4-3, “1” refers to

cylinder, #1 (the first cylinder in the firingorder), “2” refers to cylinder #8 (the secondcylinder in the firing order), “3” refers tocylinder #7 (the third cylinder in the firingorder), etc.

2. OFFSET ENTRIES - The offset entries arelisted in crankshaft degrees, andcorrespond to the position of the magneticpick-up receptacle in relation to TDC forthe individual cylinders.

Figure 4-11. Enter Offset Chart.


Page 4-18

F. USE OF TORQUE COMPUTER(Figure 4-12)

1. Using torque adapters, tighten engine toengine mount capscrews to 37 lb ft (50N•m). Tighten insulator to engine mountcapscrews to 37 lb ft (50 N•m). Tightenframe bracket to insulator nuts to 60 lb ft(82 N•m).

2. Using a 3/4 inch torque adapter, tightentransmission mount to transfer caseadapter capscrews to 65 lb ft (88 N•m).

To approximate the correct torque setting whenusing a click-type torque wrench with an adaptorfollow the directions as follows:

a. Adjust the micrometer to the desired torquesetting.

b. Determine the effective length “A” from thecenter of handle to center of square drive.

c. Determine “A + B”.

d. Compute corrected toque setting.

e. Adjust micrometer to corrected torquesetting.

f. Redetermine effective length “A” for newtorque setting.

g. Redetermine “A + B”.

h. Compute final corrected torque setting.

i. Adjust micrometer to final corrected torquesetting.

The final derived torque setting is anapproximation only of the true setting. Steps (f)through (i) must be repeated if greater accuracyis required.

Figure 4-12. Computing Torque when using Extensions.

For use with adapters ONLY. Handle extensions NOT recommended.

EXAMPLE:1. MULTIPLY LENGTH OF TORQUE WRENCH 20" BY DESIRED TORQUE 200 FT LBS 20 x 200=4000.2. ADD LENGTH OF TORQUE WRENCH 20" TO LENGTH OF ADAPTER 6" 20 + 6=26.3. DIVIDE FIRST ANSWER (4000) BY SECOND Answer (26). 4000/26=APPROXIMATELY 154 FT LBS.

154 FT LBS WILL BE THE READINGON THE TORQUEWRENCH WHEN THEDESIRED TORQUE OF 200 FT LBSIS ACHIEVED AT THE NUT.

TORQUE WRENCH IS MEASURED FROM CENTEROF SOCKET END TO PIVOT POINT IN HANDLEOR IF SOLID TO END OF HANDLE.

TORQUE WRENCH AND ADAPTER MUSTBE USED ONLY IN A STRAIGHT LINE.

EXTENSION

19

Section 4. Engine

CAUTION

Because of the high compression ratioof this engine (21.5:1), do not attempt toadd oil to any cylinder as a means ofisolating the problem to valves or ringsbecause a hydrostatic lock could occurthat can result in extensive enginedamage. In extreme cases, connectingrod or piston damage can result.

5. Crank engine, allow engine to crank longenough to accumulate six compressionpulses, and record highest reading.

6. Repeat steps (4) and (5) for remainingcylinders.

7. All cylinders should build up quickly andevenly to a minimum of 380–400 psi (2625to 2760 kPa) and lowest reading should notbe less than 80% of highest cylinder reading.

NOTE

Normal Compression - Compressionbuilds up quickly and evenly to specifiedcompression on each cylinder.

Piston Rings Leaking - If the problem is poorpiston rings, this is generally evidenced by thefact that the compression reading on the gaugewill be low on the first stroke but tends toincrease on the remaining cranking strokes toa reading that is still less than the minimum of380 psi (2625 kPa).

G. ENGINE COMPRESSION TEST• Engine must be up to normal operating

temperature.

• No reading should be lower than 380psi (2625 kPa).

• Cranking speed must be at least 180RPM.

• The lowest reading should not be lessthan 80% of the highest.

• In order to receive an accuratecompression reading, the batteries mustbe at or near a full state of charge in orderto crank the engine over fast enough. Aslow cranking rate will result in a lowreading. The lowest reading obtained fromany engine cylinder should not be lessthan 380 psi (2625 kPa).

GMC 6.2L Engine Compression Check. Acompression check can be performed at anytime on the engine to establish the mechanicalcondition of the valves and rings.

1. Remove all glow plugs.

2. Remove air cleaner element.

3. Disconnect lead 54A from fuel injectionpump.

4. Install compression gauge adapter in glowplug hole of cylinder being tested andconnect compression gauge.


Page 4-20

H. CHECK FOR ENGINE MECHANICALOR HYDRAULIC SEIZURE(Figure 4-13)

Remove all glow plugs. Using socket andbreaker bar at crankshaft pulley, rotatecrankshaft and check for mechanical orhydraulic seizure. If crankshaft will not turn,replace engine. If crankshaft turns and liquid isdischarged determine if liquid is coolant orfuel. If coolant is discharged, remove cylinderheads and check for cracked cylinder heads orleaking head gaskets. Replace cracked cylinderheads. If fuel is discharged, remove and testfuel injection nozzles. Replace defective fuelinjection nozzles.

Figure 4-13. Glow Plug RemovalEngine Seizure Check

Remove converter housing cover and checkfor damaged flywheel. Replace flywheel ifdamaged.

I. PRE-CHAMBER CRACKS(Figure 4-14)

During the service of 6.2L diesel cylinder heads,the observance of hairline cracks may be noticedin the pre-chamber area.

Cracks on the face of the pre-chamber start atthe edge of the fire slot. From the edge, thecracks proceed toward the circular impressionof the head gasket bead.

These cracks are a form of stress relief and arecompletely harmless up to a length of 5mm(3/16"). Cracks longer than this are approachingthe head gasket sealing bead and should bereplaced with the proper part number.

This illustration of a pre-chamber displays bothacceptable and unacceptable cracks.

Figure 4-14. Pre-chamber Cracks.

21

Section 4. Engine

J. NOISY VALVES & VALVE SPRINGCHECK (Figure 4-15)

To check valve spring and valve guideclearance, remove the valve covers:

Occasionally this noise can be eliminated byrotating the valve spring and valve. Crankengine until noisy value is off its seat. Rotatespring. This will also rotate valve. Repeat untilvalve becomes quiet. If correction is obtained,check for an off square valve spring. If spring isoff square more than 1/16" in free position,replace spring.

Figure 4-15. Valve Spring Check.

K. VALVE LIFTER DIAGNOSIS

1. Momentarily noisy when engine is started:

This condition is normal. Oil drains fromthe lifters which are holding the valvesopen when the engine is not running. It willtake a few seconds for the lifter to fill afterthe engine is started.

2. Intermittently noisy on idle only,disappearing when engine speed isincreased:

• Intermittent clicking may be an indicationof a pitted check valve ball, or it may becaused by dirt.

• Correction: Clean the lifter and inspect. Ifcheck valve ball is defective, replacelifter.

3. Noisy at slow idle or with hot oil, quiet withcold oil or as engine speed is increased:

High leak down rate. Replace suspect lifter.

4. Noisy at high speeds and quiet at lowspeeds:

• High oil level - Oil level above the “Full”mark allows crankshaft counterweightsto churn the oil into foam. When foam ispumped into the lifters, they will becomenoisy since a solid column of oil is requiredfor proper operation.

Correction: Drain crankcase oil untilproper level is obtained.

• Low oil level - Oil level below the “Add”mark allows the pump to pump air at highspeeds which results in noisy lifters.

Correction: Fill crankcase until proper oillevel is obtained.

• Oil pan bent on bottom or pump screencocked or loose; replace or repair asnecessary.


Page 4-22

M. LEAKING CYLINDER HEAD GASKET

Pre-chambers must not be recessed into thecylinder head or protrude out of the cylinderhead by more than .002" or a head gasket leakmay result.

This measurement should be made at two ormore points on the pre-chamber where the pre-chamber seats on the head gasket heat shieldand sealing ring. Using a straight edge and athickness gage or dial indicator, measure thedifference between the flat of the pre-chamberand the flat surface of the cylinder head. A slightvariance from one side of the pre-chamber tothe other provided both sides are within thetolerance will result in a good seal.

The sealing surface is the wire ring in the gasketwhere it contacts the block and head. Anydamage to these surfaces will result in gasketleaks. Use of the motorized wire brush or grindercould remove a few thousands of metal. Thehead may then clamp the body of the gasketrather than the sealing ring.

While the cylinder heads are off the engine,they should be carefully inspected for a numberof possible conditions, one of which is warpage,if any cylinder head is warped more than .006"longitudinally, .003" transversely, it should bereplaced; resurfacing is not recommended.

Minor surface cracks in the valve port area ofthe cylinder head, especially between the intakeand exhaust valve ports, are not a normalcondition. These surface cracks may affect thefunction of the cylinder heads and they mayrequire replacement for this condition. The useof magnaflux or dye check is recommended ascracks in the cylinder head that affectperformance are not always readily visible tothe naked eye, checking is necessary.

L. V-8 DIESEL HEAD GASKETLEAKAGE

There are various reasons why a cylinder headmay not seal, that should be detected before ahead gasket is replaced. Some may not bereadily apparent to the technician because thetheory of sealing is not fully understood.

First get an understanding of what is going onin the engine and what the gasket mustaccomplish. The pressure within the dieselengine cylinder is much higher than a gasolineengine, 1000 vs.. 600 psi.

The sealing concept is to use most of theclamping load, about 75%, to seal thecompression. This is accomplished by placinga round wire ring inside of a thin metal shieldthat surrounds the cylinder bore. When thebolts are tightened there is line contact aroundthe bore between the cylinder head and theblock. Because it is line contact, the pressureexerted by the ring to the head and block isextremely high. The clamping load is used tocompress the metal ring. The body of thegasket is a few thousands of an inch thinnerthan the ring after it is crushed. Therefore noneof the clamping load is used to crush the body.The colored rings around the various holes inthe gasket are a cured RTV sealer. The sealeris about .005 inches in thickness, on each side.It is thick enough so that it gets crushed betweenthe head and block. The sealer keeps thecombustion gases from going into the coolantand keeps the coolant from leaking out throughthe gasket.

The gasket has another feature that needsexplanation. The wire ring must cross over thepre-chamber which should be flush with thehead.

23

Section 4. Engine

There is an indentation in the block and headsurface where the sealing ring contacts bothparts. While this appears to be quite deep, actualmeasurements have shown that the groove isonly one or two thousands deep and does notaffect sealing. There are gaskets available thatare used with .030 inch oversize pistons. Use ofthese head gaskets will move the sealing beadoutboard of the existing groove. These gasketswill be used in the various kits.

Another condition is one that is evident by lookingat the gasket once it is located on the dowel pinson the block. The sealing bead is only slightlylarger in diameter than the bore. The bead mayextend into the chamfer at the top of the cylinderwhich results in an uneven crush of the wire andafter a few miles will result in a leak.

To check for this lay the old gasket on the block.Look at each cylinder, the gasket should beconcentric with the bore. It may help to pull themetal ring out of the gasket so the block is morereadily visible.

Make sure that the bolt holes in the cylinder blockare drilled and tapped deep enough. The headshould be placed on the block without a headgasket. Then run a .005 feeler gauge around theedge of the head. There should be no clearance,this indicates that dowel pins are not holding thehead off the block. Then by hand, screw each ofthe bolts in. The bolts should screw in far enoughto contact the head. This will indicate that theholes are drilled deep enough.

The bolt threads should be wire brushed to cleanthem and then coated with a sealant lubricant.This should be on the threads and under theheads of the bolts. This is critical so that the

friction on the bolt is reduced during installation.Do not put the oil in the bolt hole, an excessiveamount of oil could cause a hydraulic lock andprevent the bolt from tightening up. Do not paintthe head gasket with a sealant. Sealants willsometimes attack the RTV sealer which results ina leak.

N. DIESEL HEAD GASKET PRE-INSTALLATION INSPECTION

Check for the following contitions:• See if dowel pins hold head off block.

• Dowel pins missing.

• Cylinder heads are not warped more than.006 inches longitudinally and .003"transversely.

• Pre-chamber + .002" inches from head.

• Damage in sealing ring area.

• Damage in seal area around water passage.

• Water passage seal surrounds all waterpassages.

• Chips in bolt holes.

• Bolt holes in cylinder block drilled and tappeddeep enough.

Wire brush head bolts to clean threads.

Apply sealant to bolt threads and under head ofbolt.

Follow torque sequence and installation torqueprocedure.


Page 4-24

1

Section 5. Brakes

SECTION 5BRAKES

One reason why the hydro-boost unit is beingused is that Federal regulations are requiringthat vehicles stop in a fewer number of feetwhile at the same time using less pedal pressureto do it. This could be done with a largervacuum unit but its great size would be aproblem.

The unit’s smaller size has made it easier to fitin the engine compartment and has eliminatedthe need for a remote or frame mounted boosterpreviously used on some truck applications.

Another reason for Hydro-boost application isthe lack of adequate vacuum produced in dieseland turbocharged engines. The reliance on thepower steering pump for assist is independentof vacuum supply.

A. WHAT IS HYDRO-BOOST?

Hydro-boost is a hydraulically operated powerassist mechanism that is used to increase fluidpressure in the brake system while at the sametime decreasing pedal effort. This unit does thesame job as a vacuum booster and is connectedin the brake system much the same way.

The major difference between the two is thatthe hydro-boost unit uses pressurized powersteering fluid to obtain its assist power, thevacuum unit depends on manifold vacuum andatmospheric pressure for its assist power.

B. WHY HYDRO-BOOST?

If the hydro-boost does the same job as thevacuum booster, why change?

BRACKET

“O” RING

OUTPUT ROD(RETAINED BY

“O” RING

POWER PISTON/ACCUMULATOR

HOUSINGCOVER

HOUSINGSEAL SPOOL

VALVE

PISTONSEAL

WHEN INSTALLING SPRINGPUSH SPRING UNTIL IT SEATS

BEHIND LEDGE HOUSING

POWER PISTONRETURN SPRING

RETURN PORTFITTING

“O” RING

SPOOL VALVESLEEVE

HOUSING


Page 5-2

C. HYDRO-BOOST II

Hydro-boost II is constructed much the sameas Hydro-boost with an open center spoolvalve and hydraulic cylinder combined with agas filled accumulator. The difference betweenHydro-boost and Hydro-boost II is the locationand size of the accumulator which makes thepower unit itself smaller than previous designs.

Hydro-boost II has a reserve accumulatorsystem which stores sufficient fluid underpressure to provide one power assisted brakeapplication in the event normal oil pressure islost.

Normal application of the brake system inHydro-Boost II is as follows: With pressurefrom the steering pump entering and passing

Figure 5-2. Cutaway.

through the Hydro-boost housing, high pressureoil is always present for brake application . Seefigure 5-2.

Pushing on the brake pedal presses the inputrod forward into the cavity at the cowl end of theaccumulator/power piston.

The anchoring point at the bottom of the Ieveris spring-loaded against the power piston; ittransfers the forward movement of the applylever to the spool valve actuator sleeve. Theactuator sleeve on the cowl end of the spoolvalve begins moving forward pushing againstthe spring which reacts against the spool valvemoving it toward the apply position.

3

Section 5. Brakes

This uncovers the sealing land allowing highpressure oil to pass through the interior of thespool valve exiting at the rear past the checkball.

The movement of the spool valve first closesthe reservoir port, then opens the pump port toallow pressurized fluid into the power cavity.This pressurizes the power section and forcesthe power piston forward applying the brakes.

As the high pressure oil enters the boost cavity,it presses on the rear of the power pistonforcing the piston toward the enginecompartment and applying pressure throughthe master cylinder to the brakes.

This movement of the spool valve also reducesthe opening of the gear port. This restricts theflow of fluid to the gear, but at no time is the flowcompletely stopped.

By restricting the flow of the fluid the powersteering pump increases the pressure in thehydraulic lines.

As pressure is applied to the power piston, highpressure oil enters between the bore end andthe input rod, in effect moving the power pistonfarther and faster than the input rod. Thisprovides pedal braking feel to the driver andrequires less pedal travel to move the powerpiston.

Pressure is increased because the powersteering pump is a constant displacement type.

With no restriction the pump will maintain apressure of 100 to 150 PSI.

With full restriction the power steering pumpwill produce 1450 PSI; a relief valve limits thebuildup to that pressure.

The pressure in Hydro-boost II is limited at1100 PSI. A pressure limiting sleeve and springare installed on the engine compartment end ofthe spool valve. Pressure limiting takes placeas the actuator sleeve assembly compressesits spring which compresses the spring at thepressure limiting sleeve end and the spoolvalve travels into the bore. As oil pressuremounts, oil presses on the pressure limitingsleeve end opposing the direction of spoolapplication. At 1100 PSI, the hydraulic pressurecombined with limiter spring pressure willovercome movement of the spool valve andlimit its travel. At this point, a controlled bleedsituation exists limiting pressure.

The pressure limiting sleeve prevents thereservoir port from complete passage cut off.Pressure limiting sleeve is .006 in. Iarger thanthe spool valve opposing hydraulic area.Therefore, it has the hydraulic pressureadvantage.

Note the undercut area and through passage inthe spool between the steering gear supply grooveand cowl end of the spool valve. This is a safetypassage which supplies gear pressure in casethe normal supply route becomes shut off.

D. TROUBLESHOOTING

The hydro-boost differs from vacuum brakeboosters not only in the source of power(hydraulic versus vacuum) but in the fact that itis also a part of another major subsystem of thevehicle—the-power steering system. Therefore,problems or malfunctions in the steering systemmay affect the operation of the booster, just asa problem in the booster may affect the steeringsystem. The following noises are associatedwith the Hydro-Boost system and may or maynot be cause for customer complaint. Someare normal and for the most part temporary in


Page 5-4

nature. Others may be a sign of excessivewear or the presence of air in either the boosteror the steering system.

1. Moan or low frequency hum usuallyaccompanied by a vibration in the pedaland/or steering column may be observedduring parking maneuvers or other verylow speed maneuvers. This may be causedby a low fluid level in the power steeringpump or by air in the power steering fluiddue to holding the pump at relief pressure(steering wheel held all the way in onedirection) for an excessive amount of time(more than 5 seconds). Check the fluidlevel and fill to mark. System must sit for Ihour with the cap removed to remove theair. If the condition persists this may be asign of excessive pump wear and the pumpshould be checked following the shopmanual procedure.

2. At or near power runout (brake pedal nearfully depressed position), a high speedfluid noise (faucet type) may be heard.This is a normal condition and will not beheard except in emergency brakingconditions.

3. Whenever the accumulator pressure isused, a slight hiss may be noticed. It is thesound of the hydraulic fluid escapingthrough the accumulator valve, and iscompletely normal.

4. After the accumulator has been emptied,and the engine is started again, anotherhissing sound may be heard during the first

brake application or the first steeringmaneuver. This is caused by the fluidrushing through the accumulator chargingorifice. It is normal and will only be heardonce after the accumulator is emptied.However, if this sound continues, eventhough no apparent accumulator pressureassist was made, it could be an indicationthat the accumulator is not holding pressureand should be checked using the procedurefor Accumulator Leakdown Test.

5. After bleeding, a “gulping” sound may bepresent during brake applications as noted inthe bleeding instructions in the service manual.

Prior to performing the booster function tests, orthe accumulator leakdown test, the followingpreliminary checks must be made.

1. Check all power steering and brake lines andconnections for leaks and/or restrictions.

2. Check and fill brake master cylinder withbrake fluid. CAUTION: Power steering fluidand brake fluid cannot be mixed. If brakeseals contact steering fluid or steering sealscontact brake fluid, seal damage will result.

3. Check and fill power steering pump reservoirwith power steering fluid. Insure fluid is notaerated (air mixed with fluid).

4. Check power steering pump belt for tensionand/or damage. Adjust if necessary.

5. Check engine idle speed and adjust ifnecessary.

6. Check steering pump pressure.

5

Section 5. Brakes

Overhaul with spool plug seal kit.

Overhaul with new seal kit.

Disassemble and clean steeringsystem and Hydro-Boost II.

Replace line.

Overhaul with input assembly kit.


Tighten belt.

Fill reservoir and check forexternal belts



Overhaul with power piston/accumulator kit.


Page 5-6

E. SEAL LEAKS

1. Input Rod Seal: A damaged seal will showup as a fluid leak onto the drip pan from themounting bracket vent hole.

2. Power Piston Seal: Power piston sealdamage will be noticed by fluid leaking outat the common master cylinder-brakebooster vent and a possible reduction inpower assist. The booster must be removedfrom the vehicle and disassembled. Thepiston should be checked for any scratchesthat may be the cause of the leak. Ifscratches are present, then the powerpiston must be replaced. If no excessivescratches are present, replace theappropriate seals.

3. Housing Seal: If the housing seal isdamaged, fluid will leak out from betweenthe two housings onto the drip pan. Thebooster must be removed from the vehicleand disassembled. Replace the housingand power piston seals.

4. Spool Valve Plug ‘’O” Ring Seal: Damageto this seal will be noticed by fluid leakingout past the plug The master cylinder shouldbe disconnected from the booster. Insert asmall punch into the hole in the front housingand remove the retaining ring from thebore. Some models do not have this hole inthe front housing. On these units, use asmall screwdriver to remove the retainingring.

Using pliers, withdraw the plug from thebore. Remove the “O” ring from the plugand replace with a new one. Clean any dirtor rust from the plug bore using freshpower steering fluid. Insure that no dirt orrust is introduced into the booster. Pushthe end plug back into the bore and securewith a new retaining ring

5. Accumulator Piston Seals. Plunger SeatSeal Ring& and Check Valve Seal Ring:Any damage to these seals would causeinternal leakage. This would cause theaccumulator to leak down resulting in theloss of reserve stopping. Seals must bereplaced with their assemblies.

6. Accumulator “O” Ring Seal: Damage tothis seal will result in fluid leakage past theaccumulator spring cap.

F. HYDRO-BOOST DIAGNOSIS

a. Booster Functional Tests

1. With the engine stopped; depress the brakepedal several times to eliminate allaccumulator reserve from the system.

2. Hold the brake pedal depressed withmedium pressure (25 to 35 Ibs.), start theengine. If the unit is operating correctly, thebrake pedal will fall slightly and then pushback against the driver’s foot, remaining atabout the same position. If the booster isnot operating correctly, the trouble may beone of the following causes.

7

Section 5. Brakes


Page 5-8

9

Section 5. Brakes

b. Leakdown Test

1. Start engine and turn the steering wheeluntil the wheels contact the wheel stopslightly. Hold for a maximum of five seconds.Then release the steering wheel and turnoff the engine.

2. Depress and release the brake pedal. Thereshould be a minimum of three powerassisted brake applications before a hardpedal is obtained.

3. Restart the engine and turn the steeringwheel until the wheels contact the wheelstops lightly. There should be a light hissingsound as the accumulator is charged. Holdsteering wheel lightly against stop for amaximum of five seconds. Then releasethe steering wheel, and turn off the engine.

4. Wait one hour and apply brake pedal (donot restart the engine). There should stillbe a minimum of three power assistedbrake applications before obtaining a hardpedal;

5. If either of these preliminary checks showsthat the accumulator is not holding itscharge, the trouble may be one of thefollowing causes.

G. PARKING BRAKE LIGHT SWITCHTEST (Figure 5-3)

Disconnect leads 67C and 67E from parkingbrake switch. Using multimeter, check forcontinuity between each terminal on parkingbrake switch with parking brake engaged. Ifcontinuity is not present, replace parking brakeswitch. Reconnect leads 67C and 67E.

Disconnect lead 67D from parking brakewarning lamp. Using multimeter check forcontinuity between lead 67D and groundwith parking brake engaged. If continuity isnot present, repair body wiring harness.

Disconnect lead 27L from parking brakewarning lamp. Using multimeter, check forbattery voltage at lead 27L with rotary switchin “RUN”. If battery voltage is present, replacebrake warning lamp. If battery voltage is notpresent, repair body wiring harness.

Figure 5-3. Parking Brake Switch.


Page 5-10

H. BLEEDING THE HYDRO-BOOSTSYSTEM

Whenever the booster is removed and installed,the steering system should be bled.

NOTE

The power steering fluid and brake fluidcannot be mixed. If the brake sealscontact steering fluid or the steeringseals contact brake fluid, seal damagewill result.

1. Fill the power steering pump reservoir tothe proper level and let the fluid remainundisturbed for at least two minutes.

2. Start the engine and run momentarily. Addfluid it necessary.

3. Repeat steps 1 and 2 until the fluid levelremains constant after running the engine.

4. Raise the front of the vehicle so the wheelsare off the ground. Support the vehicle withsuitable safety stands.

5. Turn the wheels from stop to stop lightcontacting the stops. Add fluid if necessary.

6. Lower the vehicle.

7. Start the engine and depress the brakepedal several times while rotating thesteering wheel from stop to stop.

8. Turn the engine off and pump the brakepedal 4 to 5 times.

9. Check brake fluid level. Add fluid ifnecessary.

10. If the fluid is extremely foamy allow thevehicle to stand a few minutes with theengine on. Then repeat steps 7, 8 and 9.

11. Check for the presence of air in the oil. Air inthe oil will give the fluid a milky appearance.Air in the system will also cause the fluid levelin the pump to rise when the engine is turnedoff.

I. BRAKE FLUID

Silicone brake fluid (BFS) in your vehicle shouldbe purple. Sometimes, though, the dye thatgives it the purple color breaks down, and thefluid in the master cylinder becomes brown oramber.

There’s no cause for alarm if the color changes.The dye does not affect the performance of thebrake fluid.

If the fluid is not purple however, you can’t tellwhat kind of fluid is in your brake system. Youmight have a vehicle with the older HB brakefluid, and you shouldn’t mix the brake fluids.Here are two ways to tell what kind of brakefluid you have:

1. Mix a few tablespoons of the unknown fluidwith a little BFS.

2. If the two mix, it’s BFS. If the two fluidsseparate into layers, the unknown fluid isHB, and the vehicle brake fluid needs to bechanged.

3. Put some of the unknown fluid in a jar witha little water and shake it. BFS does not mixwith water, and distinct layers will be visible.Water mixes with HB, on the other hand,and will remain mixed. Separate layers willnot be visible.

1

Section 6. Transmission

SECTION 6TRANSMISSION

A. MODULATOR MAINTENANCE ANDADJUSTMENT (Figure 6-1 and 6-2))

Removal:

WARNING

Allow transmission to cool beforeperforming this task. Failure to do thismay cause injury.

1. Pull off cable clip from modulator controlrod head.

2. Loosen mounting nuts and securingmodulator cable to cable bracket andremove cable and washer from bracket .

3. Underneath vehicle, remove capscrew andmodulator retaining clip from transmission.

NOTE

Have drainage container ready to catchfluid.

4. Remove modulator and “O” ring seal fromtransmission. Discard “O” ring seal.

5. Adjust to 1-1/2" (3.18 cm) maximum travelfrom idle to wide open throttle.

6. Tighten mounting nuts and and recheckalignment. Readjust if alignment haschanged.

7. Pull modulator cable core outward andconnect cable clip to modulator control rodhead.

8. Check modulator cable for ease andsmoothness of operation and ensure cablereturns to the idle position.

Figure 6.3. Modulator Maintenance and Adjustment.


Page 6-2

9. Remove modulator cable at transmissionand measure depth of cable pinch pin. Depthmust be 0.590-0.600 inch (14.98-15.24 mm).Replace modulator if pin depth is not withinspecifications.

CABLE PINCHPIN

0.590–0.600 in14.98–15.24 mm

Figure 6-2. Moudlator Pinch Pin Depth.

10. Check modulator valve for damage andfreedom of movement in its bore. Replacemodulator valve if damaged.

11. Check transmission case for damage orporosity at modulator valve. Replacetransmission case if damaged or porous.

B. TRANSMISSION OIL PRESSURETESTS (Figures 6-6 and 6-7)

Oil Pressure Diagnostic Test

1. Remove pipe plug (3) from line pressureport (2) on left side of transmission (1).

2. Connect oil pressure gage to line pressureport (2).

WARNING

Direct all personnel to stand clear ofvehicle before starting engine.Transmissions slipping into gear maycause injury.

3. Start engine and check for leaks atconnections.

4. Bring engine to operating temperature. Checkand adjust modulator cable if needed.

5. Place transmission shift lever in “N” (neutral)and operate engine at 1,000 RPM, notepressure reading. Pressure should be 55-70psi (379-483 kPa).

3


10. Apply service brakes and placetransmission shift lever in “R” (reverse) andoperate engine at 1,000 RPM, note pressurereading. Pressure should be 95-100 psi(655-1034 kPa).

11. Activate kickdown switch manually or throughthe use of an electrical jumper lead. Applyservice brakes and place transmission shiftlever in “D” (drive) and operate engine at1,000 RPM, note pressure reading. Pressureshould be 90-110 psi (621-758 kPa).

NOTE

Next pressure test must be performedduring a road test or with vehicle raisedand tires off the ground. Pressure must berecorded at RPM specified with closedthrottle.

12. Place transmission shift lever in “D” (drive)and take foot off brake. Operate engine at2,000 RPM, close throttle (foot off accelerator)and take pressure reading when engine RPMis between 2,000-1,200. Pressure should be55-70 psi (379-483 kPa).

CAUTION

Total running time for next five tests shouldnot exceed two minutes.

6. Apply service brakes and place transmissionshift lever in “D” (drive), and allow engine toidle, note pressure reading. Pressure shouldbe 60-85 psi (414-586 kPa).

7. Apply service brakes and place transmissionshift lever in “D” (drive) and operate engine at1,000 RPM, note pressure reading. Pressureshould be 60-90 psi (414-621 kPa).

8. Apply service brakes and place transmissionshift lever in “2” (low 2) and operate engine at1,000 RPM, note pressure reading. Pressureshould be 135-160 psi (931-1103 kPa).

9. Apply service brakes and placetransmission shift lever in “1” (low 1) andoperate engine at 1,000 RPM, note pressurereading. Pressure should be 135-160 psi(931-1103 kPa).

Figure 6-6. Transmission Oil Pressure Test Hook-up.


Page 6-4

Compare oil pressure test results to information in Table 1.

Neutral1000RPM

DriveIdle

RPM

Drive1000RPM

Low 21000RPM

Low 11000RPM

Reverse1000RPM

Drive1000 RPMKick-Down

SwitchActivated

Road TestOnly

Drive *2000 RPM

ClosedThrottle

CheckTransmission

ForMalfunctions

In:

NormalPressure

Normal High High Normal Normal Normal Normal High

High

Normal

Normal

Normal

High High Normal

Normal

Low ToNormal

NormalNormal Normal

Normal

Normal

Normal

Normal

Low ToNormal

Low ToNormal

Low ToNormal

Low ToNormal

Low ToNormal

ForwardClutch Oil

Normal Low

Low

High

Normal NormalTestResults

Normal Feed DetentSystem

Normal Normal Direct ClutchOil Feed

DetentSystem

ModulatorSystem

** **

55-7090-11095-150135-160135-16060-9060-8555-70

1 2 3 4 5 6 7 TEST CONDITIONS

8

* Modulator cable and linkage held in full throttle position.** Oil pressure not important under test conditions indicated.

NOTE

Make sure that the modulator cable is properly adjusted.An improperly adjusted cable will give false pressure readings.

TABLE 6-1

Table 1. Oil Pressure Diagnosis.

5


13. Remove oil pressure gage from transmission (1) and install pipe plug (3) in line pressureport (2).

Figure 6-7. Transmission Oil Pressure Gage Removal.


Page 6-6

C. TRANSMISSION CONTROL VALVEAND GOVERNOR PRESSURE TEST(Figure 6-7)

Control Valve and Governor LinePressure Test

1. Remove pipe plug (3) from line pressureport (2) on left side of transmission (1).

2. Connect oil pressure gage to line pressureport (2).

WARNING

Direct all personnel to stand clear ofvehicle before starting engine.Transmission slipping into gear maycause injury.

NOTE

This test must be performed with vehicleraised and tires off the ground.

3. Start engine and check for leaks atconnections.

4. Bring engine to operating temperature.

5. Hold modulator linkage in the full extendedposition during testing.

6. Apply service brakes, place transmissionshift lever in “D” (drive) and take foot offbrake. Operate engine at 1,000 RPM andnote pressure reading.

7. Slowly increase engine speed to 3,000RPM and determine if line pressure dropsbelow the reading recorded in step 6.

8. If line pressure drops more than 10 psi(69 kPa) remove control valve and inspectfor damage. Replace control valve ifdamaged.

9. If line pressure drops less than 10 psi (69kPa):

a.Remove governor and inspect fordamage, replace governor if damaged.

b.Check governor pipes, screen, andtransmission case for obstructions tofluid flow. Replace damagedcomponents.

10. Remove oil pressure gage fromtransmission (1) and install pipe plug (3) inline pressure port (2).

7


and move transmission shift lever to “2”(low 2). Transmission should downshiftto 2nd gear. An increase in engine RPMand an engine braking effect should benoticed.

5. Position transmission shift lever in “2”(low 2) and with vehicle speed atapproximately 25 m.p.h., close throttleand move transmission shift lever to “1”(low 1). Transmission should downshiftto 1st gear. An increase in engine RPMand engine braking effect should benoticed.

6. Position transmission shift lever in “R”(reverse) and check for reverse operation.

E. TRANSMISSION DETENT SOLENOIDRESISTANCE TEST (Figure 6-8)

Check for damaged detent solenoid. Usingmultimeter, test solenoid coil resistance.Resistance should be 60-70 ohms. Replacesolenoid if damaged.

D. TRANSMISSION ROAD TEST

1. Position transmission shift lever in “D”(drive) and accelerate vehicle from 0 m.p.h..A 1-2 and 2-3 shift should occur at allthrottle openings. Shift points will vary withthrottle openings. Allow vehicle todecrease in speed to 0 m.p.h. and 3-2 and2-1 shifts should occur.

2. Position transmission shift lever in “2”(low 2) and accelerate vehicle from 0 m.p.h..A 1-2 shift should occur at all throttleopenings (no 2-3 shift can be obtained inthis range). The 1-2 shift in “2” (low 2) issomewhat firmer than in “D” (drive). Thisis normal.

3. Position transmission shift lever in “1”(low 1) and accelerate vehicle from 0 m.p.h..No upshift should occur in this range.

4. Position transmission shift lever in “D”(drive) and with the vehicle speed atapproximately 35 m.p.h., close throttle

Figure 6-8. Transmission Detent Solenoid Resistance Test.


Page 6-8

F. TRANSMISSION KICK-DOWNSWITCH TEST & ADJUSTMENT(Figure 6-9)

NOTE

Prior to removal, tag leads for installation.

a. Removal

1. Disconnect engine harness leads 315A (5)and 315B (4) from kick-down switch (3).

2. Remove two capscrews (1) securingswitch (3) to fuel injection pump (2).

3. Remove switch (3) from injection pump(2).

b. Installation

1. Install kick-down switch (3) to injectionpump (2), and secure with two capscrews(1).

2. Connect leads 315A (5) and 315B (4) tokick-down switch (3).

c. Adjustment

NOTE

Kick-down switch must be adjustedwhenever it is replaced or, when injectionpump is replaced.

Figure 6-9. Kick-down Switch Adjustment.

9


1. Disconnect throttle return spring (6) fromthrottle shaft lever (7) and accelerator cablebracket (9).

2. Disconnect engine harness leads 315A (5)and 315B (4) from kick-down switch (3).

3. Connect multimeter to leads on kick-downswitch (3) to read continuity.

4. Loosen two capscrews (1) to allow movementof kick-down switch (3).

5. Position feeler gage set at 0.295 inch(7.493 mm) between throttle shaft lever (7)and injection pump (2) ensuring feeler gagedoes not touch screw (8).

6. Move throttle shaft lever (7) to wide openposition so throttle shaft lever (7) rests onfeeler gage.

7. Rotate kick-down switch (3) slowly untilmultimeter reads continuity through kick-down switch (3) and tighten capscrews (1).

8. Position feeler gage set at 0.310 inch (7.874mm) between throttle shaft lever (7) andinjection pump (2) ensuring feeler gage doesnot touch screw (8).

9. Move throttle shaft lever (7) to wide openposition so throttle shaft lever (7) rests onfeeler gage. Note multimeter, no continuityshould be present. If continuity is present,repeat steps 3 through 8.

10. Connect leads 315A (5) and 315B (4) to kick-down switch (3).

11. Connect throttle return spring (6) toaccelerator cable bracket (9) and throttleshaft lever (7).

G. TRANSMISSION MALFUNCTIONS

NOTES

• In the event of a major transmissionmalfunction involving the torqueconverter or oil pump, replace filter,flush oil cooler and lines beforereplenishing fluid.

• Perform the oil pressure tests and recordthe readings for use duringtroubleshooting.

• Perform a road test.

Malfunction 1.No 1-2 Upshift or Delayed Upshift

1. If oil pressure in “D” (drive) at 1000 RPM isnormal, proceed to step 2. If oil pressure ishigh, proceed to step 3.

2. Check results of control valve and governorline pressure test.

3. If oil pressure in “N” (neutral) at 1000 RPMwas normal, proceed to step 4. If oil pressurewas high. Proceed to step 7.

4.Check for damaged detent solenoid. Usingmultimeter, test solenoid coil resistance.Resistance should be 60-70 ohms. Replacesolenoid if damaged.

5. Check control valve spacer plate forobstructions. Clean or replace spacer plate.

6. Check detent valve train for stuck valves orincorrect assembly. Replace control valve ifnecessary.

7. Check modulator cable and linkage fordamage or obstruction to movement. Cablecore should move freely in its housing. Replacemodulator or linkage if damaged.

8. Check adjustment of modulator cable. Adjustmodulator cable.

END OF TESTING!


Page 6-10

Malfunction 2.1-2 Shift or Slips

1. Check transmission oil pressure responseto varying throttle openings. Pressureshould respond rapidly to quick changes inthrottle opening. If oil pressure response ispoor, proceed to step 2. If oil pressureresponse is normal, proceed to step 3.

2. Perform steps 7 through 10 of malfunction 1.

3. If oil pressure in “D” (drive) at 1000 RPM islow, proceed to step 4. If oil pressure isnormal, proceed to step 10.

4. Check oil pump for obstructed oil passagesor damage. Repair oil pump.

5. Check forward clutch seals for damage.Replace damaged seals.

6. Check center support oil seal rings fordamage. Replace damaged seals.

7. Check rear servo piston and oil seal ringsfor damage. Repair rear servo if damaged.

8. Check front accumulator piston and oilseal rings for damage. Replace controlvalve if accumulator piston componentsare damaged.

9. Check transmission case for internaldamage or porosity. Replace transmissionif case is damaged or porous.

10. Inspect control valve for nicks on machinedsurfaces or voids in casting; check 1-2accumulator valve train for stuck valves orincorrect assembly; check frontaccumulator piston and oil seal rings fordamage. Replace control valve if anydamage is found.

11. Check rear servo and rear accumulatorpistons and oil seal rings for damage. Repairrear servo if damaged.

12. Check center support bolt for looseness.Tighten to 20-25 lb-ft (27-34 N•m).

13. Air check intermediate clutch piston forproper operation. If operation is normal,proceed to step 15.

14. Check intermediate clutch piston, plates,and release springs for damage or incorrectassembly. Repair intermediate clutch pistonif damaged.

15. Check center support for missing orificeplug. Replace transmission if plug ismissing.

END OF TESTING!

11


Malfunction 4.No 2-3 Upshift or Delayed Upshift

NOTE

If malfunction only occurs at or near fullthrottle, check engine timing for properadjustment and check exhaust systemfor restrictions.

1. Perform steps 7 through 10 of malfunction1.

2. Check control valve for a stuck 2-3 valve,and misaligned or damaged gaskets.Replace control valve if damaged.

3. Check direct clutch for damage or burnedclutch plates. Repair direct clutch ifdamaged.

END OF TESTING!

Malfunction 5.2-3 Shift Soft or Slips

1. If oil pressure in “D” (drive) at 1000 RPM islow, proceed to step 2. If oil pressure isnormal, proceed to step 4.


3. Perform steps 4 through 9 of malfunction 2.

4. Perform steps 8 and 9 of malfunction 3.

5. Check front servo for broken or missingspring and leak at servo pinch Repair frontservo if damaged.

6. Air check direct clutch piston for properoperation. If piston exhibits excessiveleakage, proceed to step 7. If operation isnormal, proceed to step 8.

Malfunction 3.1-2 Shift Firm or Rough



3. Check 1-2 accumulator valve train for stuckvalves or incorrect assembly. Replacecontrol valve if any damage is found.

4. Check rear accumulator piston and oil sealrings for damage. Repair rear servo ifdamaged.

5. Check transmission case for restricted oilpassages; damage, or porosity. Removeobstructions or replace transmission if caseis damaged or porous.

6. Check for missing or incorrectly installedcheck balls. Replace missing check balls.

7. Check for damaged detent solenoid. Usingmultimeter, test solenoid coil resistance.Resistance should be 60-70 ohms.Replace solenoid if damaged.

8. Check control valve spacer plate forobstructions and damaged or misalignedgasket. Clean or replace spacer plate.

9. Check detent valve train for stuck valvesor incorrect assembly. Replace controlvalve if damaged.

10. Check oil pump for obstructed oil passagesor damage. Repair oil pump if damaged.

END OF TESTING!


Page 6-12

7. Check direct clutch piston, plates, andrelease springs for damage or incorrectassembly. Repair intermediate clutch ifdamaged.

8. Check transmission case passages forleaks. Replace transmission if case isdamaged.

END OF TESTING!

Malfunction 6.2-3 Shift Firm or Rough


2. Check front accumulator for damagedpiston, rings, and broken or missing spring;check valve to accumulator feed forobstructions. Replace control valve ifdamaged.

3. Air check direct clutch piston for leak toouter area of clutch piston; check centerpiston seal for damage. Repair direct clutchif damaged.

4. Check center support and second oil ringfor damage. Repair center support ifdamaged.

5. Perform steps 7 through 10 of malfunction1. Step 6. Perform steps 7 through 10 ofmalfunction 3.

END OF TESTING!

Malfunction 7.No Engine Braking - Second Gear

1. Check front servo piston for leaking oilrings and damaged piston. Replacedamaged components.

2. Check front accumulator piston for leakingoil rings and damaged piston. Replacecontrol valve if damaged.

3. Check front band for damage and properinstallation. Replace front band if damaged.

END OF TESTING!

Malfunction 8.No Engine Braking - First Gear

1. Check for missing or incorrectly installedcheck balls. Replace missing check balls.

2. Check transmission case for damage atcheck ball locations. Replace transmissionif case is damaged.

3. Check rear servo for leaking oil seal ringsand damaged piston. Repair rear servo ifdamaged.

4. Check rear band apply pin for proper length.Replace pin if length is not correct.

5. Check rear band for damage and properinstallation. Replace rear band if damaged.

END OF TESTING!

13


Malfunction 9.No Detent Downshifts

1. Check for damaged detent solenoid. Usingmultimeter, test solenoid coil resistance.Resistance should be 60-70 Ohms.Replace solenoid if damaged.

2. Check detent valve train for stuck valvesand incorrect assembly. Replace controlvalve if necessary.

END OF TESTING!

Malfunction 10.No Drive or Drive Slips

1.If oil pressure in “D” (drive) at 1000 RPM islow, proceed to step 2. If oil pressure isnormal, proceed to step 4.


3. Perform steps 4, 5, and 9 of malfunction 2.

4. Check forward clutch for damage andburned clutch plates. Repair forward clutchif damaged.

5. Check roller clutch for damage and properinstallation. Replace roller clutch ifdamaged.

END OF TESTING!

Malfunction 11.No Reverse or Reverse Slips

1. If oil pressure in “D” at 1000 RPM is low,proceed to step 2. If oil pressure is normal,proceed to step 4.


3. Perform step 4 and steps 6 through 9 ofmalfunction 2.

4. Check control valve spacer plate forobstructions and misaligned gasket. Cleanor replace spacer plate if necessary.

5. Check control valve for damaged or leakypassages and stuck valves or incorrectassembly. Replace control valve ifdamaged.

6. Check rear servo and accumulator pistonfor damaged oil seal rings, pistons, andband apply pinch Check for correct lengthband apply pinch Repair rear servo andaccumulator if damaged.

7. Check center support and oil seal rings fordamage and wear. Repair center support ifdamaged or worn.

8. Check direct clutch for damage and burnedclutch plates. Repair direct clutch ifdamaged.

9. Check rear band for damage and properinstallation. Replace band if damaged.

10. Check forward clutch for damage andbinding (will not release). Repair forwardclutch if damaged.

END OF TESTING!


Page 6-14

Malfunction 12.Vehicle Moves in Neutral

1. Check manual valve for damage and properinstallation. Replace manual valve ifdamaged.

2. Check detent lever and pin for damage andproper installation. Replace lever or pin ifdamaged.

3. Check oil pump for leaking oil passages anddamage. Repair oil pump if damaged.

4. Check forward clutch for damage and burnedclutch plates. Repair forward clutch ifdamaged.

Malfunction 13.Transmission Noisy

NOTE

Check engine accessory drivecomponents; water pump, power steeringpump, alternator, and air conditionercompressor (if installed) for the source of“noise” before checking transmission.

a. Noise in Neutral and All Driving Ranges

1. Check torque converter for loose mountingcapscrews and damage. Tighten capscrewsor replace torque converter if damaged.

2. Check flywheel for damage. Replace flywheelif damaged. Step 3. Check oil pump forobstructed oil passages, damage, and properassembly. Repair oil pump if damaged.

b. Noise in First, Second, and Reverse.

1. Check gear unit thrust bearings and races fordamage. Replace bearing(s) and races ifeither is damaged.

2. Inspect gears for damage and wear. Replacedamaged or worn components. Step 3.Inspect front internal gear ring for damage.Replace gear ring if damaged.

c. Noise During Acceleration - Any Gear.

Check engine and transmission mounts forlooseness or damage. Secure or replace mounts.

H. TORQUE CONVERTER END PLAYCHECK (Figure 6-11)

1. Screw upper and lower knurled knobstogether. Be sure collet end is not expanded.

2. Insert J 35138 into the torque converter hub.

3. Slide tapered plug into torque converter hub.Plug is for alignment of tool.

4. Hold upper knurled knob and turn wing nutclockwise until hand tight to expand collet intoconverter turbine hub. Then loosen wing nut(counter clockwise) 2 turns, or until tool isloose (will move up and down) while notremovable from converter.

5. Hold upper knurled knob and turn lowerknurled knob clockwise until hand tight toclamp tool in the converter turbine hub.

6. Attach magnetic base (J 26900-13) to torqueconverter and set up dial indicator (J 8001) sothat indicator tip is in center of tool wing nut.

7. To make end play check, push upper knurledknob down, zero out dial indicator and pulllower knurled knob up. Be sure tapered plugstays seated in converter hub. End play is thedifference between up and down positions.DO NOT ALLOW WING NUT TO TURNWHEN MEASURING.

8. Remove tool by holding upper knurled knoband turning wing nut counterclockwise.

15


Figure 6-11.Torque Converter Checks.

Refer to the following chart for torque converter end play specifications. Torque converters thatexceed the maximum end play specitfications ahould be replaced.

OPEN CONVERTER ALL SIZES 0-0.50" (NON-T.C.C.). (0-1.30 MM)


Page 6-16

I. TORQUE CONVERTER LEAK TEST(Figure 6-12)

WARNING

Wear protective goggles during this testto prevent accidental damage to eyes.

1. Select proper plug and insert into torqueconverter opening.

2. Install converter leak test fixture onto torqueconverter and tighten securely.

3. Apply 60 psi air pressure into the torqueconverter.

4. The torque converter passes the air test ifthere is no drop in pressure during a 60second period.

WARNING

Release air pressure slowly to avoidspraying of oil from the leak tester.

5. Remove torque converter leak test fixtureand plug.

Figure 6-12. Converter Leak Tst Fixture.

1

Section 7. Alignment Procedures

A. TOE-IN/FRONT WHEEL CHECKAND INSPECTION(Figures 7-1, 7-2, 7-3, 7,4 and 7-5)

NOTE

• It is not necessary to perform frontwheel toe-in alignment prior to thescheduled semiannual or 3,000 mile(4,827 km) maintenance interval unlessabnormal vehicle handling or control isreported.

• Front wheel alignment adjustmentsother than toe-in are performed by DSmaintenance.

• Vehicle must be at normal operatingweight during toe-in check and/oradjustment to ensure proper alignment.

• Make sure models M1037 and M1042have S250 shelter installed beforeperforming front wheel toe-in alignment.

a. Preliminary Inspection (Figure 7-1)

1. Check all tires (6) for uniform tread wear.

2. Raise vehicle and support under lowercontrol arm (9).

3. Check geared hubs (4) for output spindleend play by grasping edges of tires (6) andattempting to move tires (6) up and down.Adjust spindle bearings if any spindlemovement is apparent.

SECTION 7ALIGNMENT PROCEDURES

4. Check for looseness of upper ball joints (3)by grasping top of tires (6), and attemptingto move tires (6) in and out. Replace upperball joints (3) if tire (6) movement at topouter edge of tires (6) is 3/8 inch (9 mm) ormore.

Figure 7-1.Toe-in Front Wheel Check and Adjustment.


Page 7-2

3. Hold a 6 inch ruler between the lowercontrol arm (2) and the capscrew (1) ongeared hub (3).

4. Push down on the prybar to try and movethe geared hub (3).

5. Measure any movement in geared hubassembly. If Movement is more than 1/8inch (0.3175 cm), replace the lower balljoint(s).

6. If ball joint makes a squeaking noise,replace it.

b. Ball Joint Inspection (Figure 7-2)

Check for looseness of lower ball joints. Withlower control arms supported.

1. Inscribe a reference point on gearedhub capscrew (1) parallel with lowercontrol arm (2) to obtain an accuratemeasurement.

2. Position prybar between lower controlarm (2) and geared hub (3).

PRYBAR

MARK HERE AND

MEASURE MOVEMENT

6" RULER

a

b

c

Figure 7-2. Lower Ball Joint Inspection.

3


NOTE

Use a flat steel plate or scrap metal toperform step (f).

6. Secure steel plate or scrap metal (10) tofront crossmember (2) with clamp (9) asshown in Figure 7-3.

7. Pull center link (1) in downward directionto seat ball and socket of idler arm (3) asshown in Figure 7-3.

8. Use flat surface (7) of center link (1) as aguide, mark reference line one (8) onsteel plate or scrap metal (10) as shownin Figure 7-3.

9. Position spring scale (3) on center link (1)and pull in an upward direction to obtain25 lb reading on spring scale (3) asshown in Figure 7-4.

c. Idler Arm Inspection(Figure 7-3, 7-4, and 7-5)

Perform an Idler arm inspection. Use thefollowing procedure to determine idler arm freeplay. Measurements can be made using aspring scale dial indicator.

1. Park vehicle on a flat surface, and makesure parking brake is engaged.

2. Block rear wheels.

3. Raise front wheels off surface, and placesupports under frame rails.

4. Set front wheels in a straight-aheadposition.

5. Check idler arm for visible damage, suchas breaks and cracks. If breaks or cracksare found, replace idler arm.

Figure 7-3. Idler Arm Inspection and Check.


Page 7-4

NOTE

During marking of reference line two,maintain 25 lb reading on spring scale.

10. Use flat surface (4) of center link (1) as aguide, mark reference line two (5) onsteel plate or scrap metal (7) as shown infigure 2. Remove spring scale (3) fromcenter link (1).

11. Remove clamp (6) and steel plate or scrapmetal (7) from front crossmember (2) asshown in Figure 7-4.

12. Measure distance between markedreference line one (3) and reference linetwo (2) on steel plate or scrap metal (1) asshown in Figure 7-5. If measurementexceeds 0.25 inch, replace idler arm.

Figure 7-4.Using a Spring Scale Dial Indicator to Check Idler Arm Free Play.

5


13. Remove supports from under frame rails.

Figure 7-5. Measuring Idler Arm Free Play.

14. Remove rear wheel blocks.

15. Check for looseness of tie rod ends (5) byattempting to move tie rods (8) verticallyand horizontally. Replace tie rod end(s) (5)if any movement is apparent.

16. Check for damaged control arm bushings(1). Replace upper control arms (2) orlower control arms (9) if bushings (1) aredamaged.


Page 7-6

d. Toe-In Check

NOTE

• Vehicle must be on level ground withwheels set straight ahead.

• Check and adjust tire pressure

• Steps 1 through 3 will determine centerlineof tire.

• “Point of Measurement” for checkingtoe-in will be where lines marked insteps 1 and 3 intersect.

1. Mark line (4) on center tread (1) of tire (2)16 inch (42 cm) from ground.

2. Measure total width of tire tread (3) andrecord.

3. Mark line (5) on center tread (1) at one-halftotal tread width (3).

4. Repeat steps 1 through 3 for opposite tire.

5. Measure distance between “Points ofMeasurement” on front side of tires (2) andrecord.

6. Rotate tires (2) by moving vehicle forwarduntil “Points of Measurement” are 16 inch (42cm) above ground at rear side of tires (2).

7. Measure distance between “Points ofMeasurement” on rear side of tires (2) andrecord.

NOTE

• If measurement is larger on front side oftires than measurement on rear side oftires, tires have toe-out.

• During vehicle operation, suspensionsystem movement may cause slightalignment changes. For this reason,Table 7-1 provides an inspectionspecification that allows a larger toe-intolerance during inspection. If, afterinspection, the toe-in is outsideinspection specifications, set toe-in tothe adjustment specifications in Table7-1.

• If toe-in alignment does not meetinspection specifications, repeatchecking procedures to eliminate anypossible reading errors.

8. Subtract measurement from front side oftires (2) step 5, from measurement fromrear side of tires (2) step 7. The result of thissubtraction represents inches of toe-inchRefer to Table 7-1 for toe-in inspectionspecifications. If toe-in does not meetinspection specifications, adjust toe-in.

7


Figure 7-5. Toe-in Measurement Check.


Page 7-8

NOTE

• Vehicles should be at curb weight to ensure proper alinement.Refer to Table 7-1(a.) for adjustment specifications.

• Table 7-1(b.) is optional and can be used when the vehicle's averageoperation is at less than gross vehicle weight. Vehicle is to be loaded toits average operating weight when using this table.

Table 7-1. Toe-In Alignment Specifications.

9


e. Toe-in Adjustment (Figure 7-6)

1. Loosen two locknuts securing two clampson each adjusting sleeve.

NOTE

Toe-in can be increased or decreased bychanging length of tie rods. A threadedsleeve is provided for this purpose. Bothtie rods must be the same length 1/8 inch(3 mm) after adjustment.

2. Turn each adjusting sleeve (8) equally, butin opposite directions.

3. Roll vehicle rearward then forward tooriginal position.

4. Repeat toe-in check and adjustmentprocedures until correct adjustment isindicated.

CAUTION

Ensure bolt and nut on adjusting sleeveclamp nearest to geared hub is facinghalfshaft. Bolt and nut on adjusting sleeveclamp nearest to frame must be facingaway (180° ) from stabilizer bar, to preventdamage to equipment.

5. Secure two clamps (10) on each adjustingsleeve (8) with two locknuts (11). Tightenlocknuts (11) to 30 lb-ft (40 N•m).

Figure 7-6. Toe-in/Front Wheel Check


Page 7-10

B. TOE-OUT REAR WHEEL CHECKADJUSTMENT(Figures 7-7, through 7-9)

NOTE

• It is not necessary to perform rear wheeltoe-out alignment prior to the scheduledsemi-annual or 3,000 mile (4,827 km)maintenance interval unless abnormalvehicle handling or control is reported.

• Rear wheel alignment adjustmentsother than toe-out are performed by DSmaintenance.

• Vehicle must be at normal operatingweight during toe-out check and/oradjustment to ensure proper alignment.

• Make sure models M1037 and M1042have S250 shelter installed beforeperforming rear wheel toe-outalignment.

a. Preliminary Inspection

1. Check all tires for uniform tread wear.

2. Raise vehicle and support under lowercontrol arms (1).

3. Check geared hubs (2) for output spindleend play by grasping edges of tires andattempting to move tires up and down.Adjust spindle bearings if any spindlemovement is apparent.

4. Check for looseness of upper ball joints (3)by grasping top of tires, and attempting tomove tires in and out. Replace upper balljoints (3) if tire movement at top outer edgeof tires is 3/8 inch (9 mm) or more.

5. Check for looseness of lower ball jointsby grasping bottom of tires, and attemptingto move tires in and out. Replace lowerball joints if tire movement at bottom outeredge of tires is 1/2 inch (13 mm) or more.

6. Lower vehicle.

7. Check for looseness of radius rod ends (4)by attempting to move adjusting sleeve (5)vertically and horizontally. Replace radiusrod end(s) (4) if any movement is apparent.

8. Check for damaged control arm bushings.Replace upper control arms or lower controlarms if bushings are damaged.

Figure 7-7. Toe-0ut Rear Wheel Check Adjustment.

11


b. Toe-Out Check

NOTE

• Vehicle must be on level ground withwheels set straight ahead.

• Steps 1 through 3 will determinecenterline of tire.

• “Point of Measurement” for checkingtoe-out will be where lines marked insteps 1 and 3 intersect.

1. Mark line (4) on center tread (1) of tire (2)16 inches (42 cm) from ground.

2. Measure total width of tire tread (3) andrecord.

3. Mark line (5) on center tread (1) at one-halftotal tread width (3).

4. Repeat steps 1 through 3 for opposite tire.

5. Measure distance between “Points ofMeasurement” on front side of tires (2) andrecord.

6. Rotate tires (2) by moving vehicle forwarduntil “Points of Measurement” are 16 inch(42 cm) above ground at rear side of tires(2).

7. Measure distance between “Points ofMeasurement” on rear side of tires (2) andrecord.

NOTE

• If measurement is larger on rear side oftires than measurement on front side oftires, tires have toe-in.

• During vehicle operation, suspensionsystem movement may cause slightalignment changes. For this reason,Table 7-2 provides an inspectionspecification that allows a larger toe-out tolerance during inspection. If, afterinspection, the toe-out is outsideinspection specifications, set toe-out tothe adjustment specifications in Table7-2. If toe-out alignment does not meetinspection specifications, repeatchecking procedures to eliminate anypossible reading errors.

8. Subtract measurement from rear side oftires (2) step 7, from measurement fromfront side of tires (2) step 5. The result ofthis subtraction represents inches of toe-out. Refer to Table 7-2 for toe-out inspectionspecifications. If toe-out does not meetinspection specifications, adjust toe-out.


Page 7-12

Figure 7-8. Toe-0ut Points of Measurement.

13


NOTE

• Vehicles should be at curb weight to ensure proper alinement.Refer to Table 7-1(a.) for adjustment specifications.

• Table 7-1(b.) is optional and can be used when the vehicle's averageoperation is at less than gross vehicle weight. Vehicle is to be loaded toits average operating weight when using this table.

Table 7-2. Toe-Out Alignment Specifications.

MODELS:M1097,M1097A1,

a. Vehicle @curbweight

b. Vehicle @normaloperatingweight(Optional)

MODELS:M998,M1025, M1026,M1035, M1038,M1043, M1044

7/16 ± 1/8 in.(11 mm ± 3 mm)

5/16 ± 1/8 in.(8 mm ± 3 mm)

MODELS:M996, M997,M1036,M1037,M1042,M1045,M1046

1/2 ± 1/16 in.(12.5 mm ± 1.5 mm)

1/2 ± 1/16 in.(12.5 mm ± 1.5 mm)

1/4 ± 1/8 in.(6 mm ± 3 mm)

1/4 ± 1/8 in.(6 mm ± 3 mm)

1/16 ± 1/16 in.(1.5 mm ± 1.5 mm)

1/16 ± 1/16 in.(1.5 mm ± 1.5 mm)

MODELS:M996, M996A1,M998, M998A1,M1025, M1025A1,M1026, M1026A1,M1035, M1035A1,M1036,M1038, M1038A1,M1043, M1043A1,M1044, M1044A1,M1045, M1045A1,M1046, M1046A1

TOE-OUT (REAR) ADJUSTMENT SPECIFICATIONS

BIAS TIRE RADIAL TIRE

1/2 ± 1/16 in.(12.5 mm ± 1.5 mm)

MODEL:M997,M997A1,M1037,M1042

1/16 ± 1/16 in.(1.5 mm ± 1.5 mm)

VEHICLEPAYLOAD


Page 7-14

c. Toe-Out Adjustment

1. Loosen two locknuts (1) securing twoclamps (3) on each adjusting sleeve (2).

NOTE

Toe-out can be increased or decreasedby changing length of radius rods. Athreaded sleeve is provided for thispurpose.

2. Turn each adjusting sleeve (2) equally, butin opposite directions.

Figure 7-9. Toe -out Adjustment.

3. Roll vehicle rearward then forward to originalposition.

4. Repeat toe-out check and adjustmentprocedures until correct adjustment isindicated.

5. Secure two clamps (3) on each adjustingsleeve (2) with two locknuts (1). Tightenlocknuts (1) to 30 lb-ft (40 N•m).

15


C. STEERING STOP CHECK &ADJUSTMENT(Figure 7-10 through 7-13)

a. Removal

1. Loosen jamnut (2) and remove steeringstop capscrew (3) and jamnut (2) fromgeared hub (1). See Figure 7-10.

2. Remove jamnut (2) from capscrew (3).

b. Installation

1. Apply sealing compound to capscrew (3).

2. Install jamnut (2) on capscrew (3).

3. Install capscrew (3) and jamnut (2) ongeared hub (1). Tighten capscrew (3) fingertight.

c. Adjustment

NOTE

Prior to adjustment ensure length of eachtie rod is the same. If tie rod lengths arenot the same 1/8 inch (3 mm), check toe-in alignment.

1. Draw a reference chalk line (6) 30 feet long.Mark this line “A”.

2. Draw another reference line perpendicularto line “A” approximately 10 feet from theend of line “A” and mark this line “D”.

Figure 7-11. Steering Stop Reference line

Figure 7-10.Steering Arm Capscrew Adjustment.


Page 7-16

2. Position vehicle so that center of left rearand left front tires are positioned directly onreference line “A” (6).

3. Using a protractor, draw a second referenceline “B” (5) at 34° where lines “A” and “D”intersect. Mark this line “B”.

Figure 7-12. Repeat.Steering stop Check and Adjustment.

4. Again, using a protractor, draw a thirdreference line “C” (4) at 36° where lines “A”,“B”, and “D” intersect. Mark this line “C”.

5. Roll vehicle forward until center of left fronttire is over intersection of lines “A”, “B”, “C”and “D”.

6. Turn steering wheel full left.

7. If the centerline of front and rear of left fronttire (7) is over area between lines “B” and“C”, no adjustment is necessary.

8. If centerline of front and rear of left front isnot over area between lines “B” and “C”,loosen jamnut (2) and turn capscrew (3) allthe way in. See Figure 7-13.

Figure 7-13.Steering Stop Adjustment and

Lower Contrtol Arm

9. Turn steering wheel until centerline of frontand rear of tire (7) is over area betweenlines “B” and “C”.

17


10. Unscrew capscrew (3) until head makescontact with wheel stop (9) on lower controlarm (8).

11. Secure capscrew (3) with jamnut (2).

12. Repeat adjustment procedure for oppositeside.

D. CASTER & CAMBER CHECK ANDADJUSTMENT PROCEDURES(Figure 7-14)

a. Caster and Camber Check

NOTE

The alignment check will be made on alevel surface with front tires in the

straight ahead position. Vehicles will bechecked at curb weight only.

1. Check caster and compare to thespecifications in Table 7-3.

2. Check camber and compare to thespecifications in Table 7-3.

3. If either caster or camber does not meetspecifications, go to caster and camberadjustment.

Figure 7-14 . Caster and Camber Adjustment.


Page 7-18

b. Caster and Camber Adjustment

NOTE

Caster and camber adjustment isbasically the same for all four wheels.This procedure covers the right frontwheel.

1. Remove wheel.

2. Remove two locknuts (7), washers (2),capscrews (1), and washers (2) securingupper control arm (8) to mounting brackets(3). Discard locknuts (7).

3. Loosen capscrews (6) and nuts (5) securingeach mounting bracket (3) to air lift bracket(4).

NOTE

Shims are available in 0.06 inch (1.52mm) and 0.12 inch (3.04 mm) thickness.

4. Add or subtract shim(s) (9) as required tobring caster and/or camber withinspecifications (table 7-3). Suspensionalignment change in relation to shimselection is shown in Table 7-4, SuspensionAlignment Change.

Figure 7-14 (Repeat). Caster and Camber Adjustment.

19


NOTE

• Subtracting shims will affect caster/camber in the opposite direction ascompared to adding shims.

• For 0.06 inch (1.52 mm) shims, reducethe values in the table by half.

• For larger changes, combinations ofadditions or subtractions will providedesired results.

5. Tighten capscrews (6) and nuts (5) securingeach mounting bracket (3) to 90 lb-ft (122N•m).

6. Secure upper control arm (8) to mountingbrackets (3) with two washers (2),capscrews (1), washers (2), and locknuts(7). Tighten locknuts (7) to 260 lb-ft (353N.m).

7. Install wheel.

Table 7-3. Alignment Specifications.

MODEL CASTERFRONT/REAR

(±1.5°)

CAMBERFRONT/REAR(±1.5°, –0.5°)

M998, M1025, M1026, M1035M1038, M1043, M1044

M966, M1036, M1037, M1042M1045, M1046

M996M M997

2.0°/0.0°

2.0°/0.0°

2.0°/0.0°

0.8°/1.7°

0.8°/1.5°

0.8°/1.7°

MODEL CASTERFRONT/REAR

(±1.5°)

CAMBERFRONT/REAR

(±1.0°)

M996, M996A1, M998, M998A1,M1025, M1025A1, M1026, M1026A1,M1035, M1035A1, M1036,M1038, M1038A1, M1043, M1043A1,M1044, M1044A1, M1045, M1045A1,M1046, M1046A1

M997, M997A1, M1037, M1042

M1097, M1097A1

+1.50°/0.0°

+1.44°/0.0°

+1.44°/0.0°

+0.68°/+1.50°

+0.68°/+1.44°

+0.38°/+2.12°

BIAS TIRES

RADIAL TIRES


Page 7-20

LOCATION REAR SUSPENSIONSHIM

CASTER CAMBER

Front shim only

Rear shim only

Front and rear shims

+0.12 inch (3.04 mm)

+0.12 inch (3.04 mm)

+0.12 inch (3.04 mm)

+0.5°

–0.5°

0.0°

–0.1°

+0.6°

+0.5°

LOCATION FRONT SUSPENSIONSHIM

CASTER CAMBER

Front shim only

Rear shim only

Front and rear shims

+0.12 inch (3.04 mm)

+0.12 inch (3.04 mm)

+0.12 inch (3.04 mm)

+0.6°

–0.6°

0.0°

–0.5°

+0.0°

+0.5°

Table 7-4. Suspension Alignment Change.

1

Section 8. Jacking Procedures

WARNING

Hydraulic jacks are used for raising and lowering, and are notused to support vehicle. Never work under vehicle unless wheelsare blocked and it is properly supported. Injury or damage toequipment may result if vehicle suddenly shifts or moves.

SECTION 8JACKING PROCEDURES


Page 8-2

C. RAISING FRONT OF VEHICLE(Figure 8-1)

1. Block rear wheels (2).

2. Center jack under front suspension frontcrossmember (6). Use a wood blockbetween jack and crossmember (6).

3. Raise vehicle (1) high enough to placetrestles (3).

4. Place trestles (3) under flat portion of framerails (7) and lower jack until weight issupported by trestles (3).

D. LOWERING FRONT OF VEHICLE(Figure 8-1)

1. Raise vehicle (1) and remove trestles (3).

2. Lower vehicle (1).

3. Remove blocks from rear wheels (2).

A. RAISING CORNER OF VEHICLE(Figure 8-1)

1. Block wheels (2) or (4).

2. Place jack under lower control arm (5) oncorner to be raised.

3. Raise vehicle (1) high enough to placetrestle (3).

4. Place trestle (3) under flat portion of framerail (7) and lower jack until weight issupported by trestle (3).

B. LOWERING CORNER OF VEHICLE(Figure 8-1)

1. Raise vehicle (1) and remove trestle (3).


3. Remove blocks from wheels (2) or (4).

3


Figure 8-1. Front and Corner Jacking Procedures.


Page 8-4

E. RAISING REAR OF VEHICLE(Figure 8-2)

1. Block front wheels (4).

2. Center jack under rear suspension rearcrossmember (6). Use a wood blockbetween jack and crossmember (6).


4. Place trestles (3) under flat portion of framerails (5) and lower jack until weight issupported by trestles (3).

F. LOWERING REAR OF VEHICLE(Figure 8-2)

1. Raise vehicle (1) and remove trestles (3).


3. Remove blocks from front wheels (4).

G. RAISING ENTIRE VEHICLE(Figure 8-2)

1. Raise front of vehicle.

2. Center jack under rear suspension rearcrossmember (6). Use a wood blockbetween jack and crossmember (6).


4. Place trestles (3) under flat portion of framerails (5) and lower jack until weights issupported by trestles (3).

5. Move blocks aside.

H. LOWERING ENTIRE VEHICLE(Figure 8-2)

1. Raise rear of vehicle (1) and removetrestles (3).

2. Lower rear of vehicle (1) and block rearwheels (2).

3. Lower front of vehicle.

5


Figure 8-2. Rear and Entire Vehicle Jacking Procedures.


Page 8-6

1

Section 9. Power Steering

A. POWER STEERING TEST & BLEEDING (Figure 9-1)

Check power steering system using powersteering analyzer and analyzer adapter.

1. Disconnect high pressure hose (1) fromhydro-boost (4) leading to power steeringpump and connect adapter (2) and analyzer(3) to hydro-boost (4). Connect adapter (6)to high pressure hose and to analyzer(3).Open valve (5) on analyzer.

2. Disconnect harness connector at fan drivesolenoid. Check fluid level in power steeringpump and add if necessary.

3. Connect tachometer for purpose ofrecording engine RPM.

4. Start engine and allow to idle. Check forleaks at connections.

5. Record pump pressure and flow. Pressureshould be 180-220 psi and flow should be2.50-3.50 gpm. If pressure or flow is toolow, check for restriction in pressure linefrom power steering pump. If pressure istoo high, check for restriction in pressureline from hydro-boost to steering gear. Ifno restrictions are found, replace powersteering pump.

6. Partially close valve (5) on analyzer sopressure increases to 300 psi and recordflow. Subtract this flow rate from flow rateobtained in step e. If there is more than 1gpm difference in flow rates, replace powersteering pump.

a

b

c

d

e

FROMPOWER

STEERINGPUMP

f

SECTION 9POWER STEERING

.Figure 9-1. Power Steering Test Hook-up


Page 9-2

CAUTION

Do not leave valve fully closed for morethan 5 seconds or pump damage willresult.

7. Close and partially open valve on analyzerthree times, record highest pressurereading each time. All three readings mustbe 1300 psi or above. If not, replace powersteering pump.

8. Open valve on analyzer and increaseengine speed to 1500 RPM. Record flow.If flow varies more than 1 gpm from flowrate recorded in step f., replace powersteering pump.

9. Turn steering wheel all the way to left andright and record flow at each stop. Flowshould drop to 1 gpm or less. If flow doesnot drop to 1 gpm or less, replace steeringgear.

10. Push brake pedal to floor and hold, flowshould drop to 1 gpm or less. If flow doesnot drop to 1 gpm or less, replace hydro-boost.

11. Turn steering wheel slightly to left or right,and release wheel quickly while watchingpressure gage. Pressure gage should snapback quickly. If pressure gage returnsslowly, replace steering gear.

12. Push brake pedal down and release quicklywhile watching pressure gage. Pressuregage should snap back quickly. If pressuregage returns slowly, replace hydro-boost.Connect harness connector to fan clutchsolenoid.

a

b

c

d

e

FROMPOWER

STEERINGPUMP

f

Figure 9-1 Repeat. Power Steering Test Hook-up.

1

Section 10. Transfer Case

SECTION 10TRANSFER CASE

A. TRANSFER CASE HOUSING STUDS(Figure 10-1)

If transfer case will not go into low range afterunit repair or replacement of adapter mountingstuds (1), check measurement of studs. Studsmust be exposed 1.250 inch to 1.300 inch. Ifnot exposed 1.250 inch to 1.300 inch, studscould be preventing transfer case from shifting.

Figure 10-1. Measuring Adapter Mounting Studs.

B. TRANSFER CASE TOWING INSTRUCTIONS

The recommended methods for towing thevehicle if it becomes disabled are as follows:

1. Flat bed towing (all wheels stationary).

2. All four wheels on the ground with TransferCase in neutral (towing speeds should belimited to 55 m.p.h. with no distancerestrictions).

3. If the Transfer Case is not operational orTransfer Case neutral is not obtainable,tow the vehicle with either the front or rearoff the ground and the opposite end on atowing dolly to prevent the wheels fromrotating their respective propeller shafts.

NOTE

When towing with all four wheels on theground, all the tires must be the samesize (air pressure equalized and samecircumference).


Page 10-2

1

Section 11. Differentials

Figure 11-1. ZEXEL Torsen® Differential.

SECTION 11DIFFERENTIALS

ground clearance. Each housing is equippedwith a disc brake assembly mounted at eachside of the output flange, and both housings areinterchangeable.

The ZEXEL Torsen® differential provides full

time differentiation, full time maximum traction,and “Torque and Load Sensing” capabilities.These features provide improved handling,steering, and enhanced off-road mobility. Thedifferential “torque” senses where power isrequired and delivers it accordingly. It resistsspinout by transferring more torque to the drivewheel with the most resistance to spinout.

OUTPUTFLANGESHAFT

RING GEAR

SPUR TEETH

ELEMENT GEARS WITH

INVEX® GEAR TEETH

SIDE GEAR

OUTPUTFLANGESHAFT

AXLECASE

A. AXLE AND DIFFERENTIAL OPERATION (Figure 11-1)

The front and rear axle housings, cast fromaluminum, are manufactured by Dana,utilizing conventional hypoid eight bolt ringand pinion gears with a ratio of 2.73:1. Bothaxle housings are equipped with a ZEXELTorsen

® differential and lubricated with

standard 80/90 Hypoid gear oil.

The housings are mounted up, between theframe rails, to minimize drive line vibrations,external damage, and provide increased


Page 11-2

Figure 11-1 Repeat. Torsen Differential.

B. OPERATING PRINCIPLE

In the ZEXEL Torsen® differential, as in any

conventional differential, power of the engineis transferred to the differential housing by thering gear. The Torsen differential is assembledwith Invex gearing comprised of three pairs ofsatellite gears (element gears) in mesh androtation with central helical gears (side gears).The side gears are splined to the axle shaftswhich provide power to the wheels.Independent rotation (differentiation) of theaxle shafts occurs when required.

The pairs of element gears are interconnectedwith each other by means of the spur teeth.The Torsen

® differential provides an increase

in the total amount of power supplied to thewheels. Power is transferred to the wheel havingthe most traction via the combination of theInvex® gear system and the frictional resistancein the differential.

Driving in a straight line, each wheel rotates thesame speed. In a turn, each wheel will rotate ata slightly different speed. The inside wheel willslow down at exactly the same rate as theoutside wheel speeds up. The difference inRPM is transferred via the 1 to 1 ratio of the spurteeth on the element gears.

OUTPUTFLANGESHAFT

RING GEAR

SPUR TEETH

ELEMENT GEARS WITH

INVEX® GEAR TEETH

SIDE GEAR

OUTPUTFLANGESHAFT

AXLECASE

1

Section 12. Electrical

B. STARTER TESTING(Figure 12-1)

WARNING

Negative battery cable must bedisconnected before disconnecting anyharness from protective control box.Failure to do so may result in injury topersonnel or damage to equipment.

SECTION 12ELECTRICAL SYSTEM

A. BATTERY SHUNT TEST ANDREPLACEMENT (Figure 12-1)

Using a multimeter, check for continuity acrossshunt in battery compartment. If continuity isnot present, replace shunt.

A I

EG

B

S

BODY HARNESSCONNECTOR

PROTECTIVECONTROL BOX STARTER

SOLENOID CASE GROUNDTO ENGINE

BLOCK

SHUNT

BATTERY12V

BATTERY12V

ENGINE HARNESSCONNECTOR

14B

14A

74A

81A

14B

6A

7A

11A ROTARYSWITCH

STARTER MOTOR

–

+

–

+

NEUTRAL STARTSWITCH

NEGATIVEBATTERY CABLE

Figure 12-1. Starting System Schematic.


Page 12-2

1. With rotary switch held in “START”, checkfor battery voltage on lead 74A at thestarter. If battery voltage is present, replacestarter.

2. Disconnect lead 14B from neutral startswitch. Check for battery voltage at neutralstart switch connector 14 with rotary switchin “START” position. If battery voltage ispresent continue to step 3. If voltage is notpresent proceed to step 7.

3. Disconnect negative battery cable and bothconnector plugs from protective controlbox. Check continuity of lead 14B at neutralstart switch to pin A at the control box bodyharness connector plug. If continuity is notpresent repair wiring harness.

4. Disconnect lead 74A from starter. Checkcontinuity of lead 74A at starter to pin I ofthe control box engine harness connectorplug. If continuity is not present, repairwiring harness.

5. Connect neutral start switch lead 14B,starter lead 74A, and both control boxconnector plugs. Disconnect lead 2A fromalternator and connect battery groundcable. Attempt to start vehicle. If starterdoes not crank, replace protective controlbox. Check continuity of lead 2A.

6. If starter cranks engine, disconnectnegative battery cable, and connect lead2A to alternator after thoroughly cleaningterminal connection area. Connect negative

battery cable and attempt to start vehicle. Ifstarter does not crank replace alternator. Ifstarter does crank, apply sealant toalternator terminal connections.

7. Disconnect lead 14A from neutral startswitch. With rotary switch in “START”position, check for battery voltage at lead14A. If voltage is present, continuity checkthe neutral start switch. Ensure the neutralstart switch is activated mechanically. Ifcontinuity is not present, replace neutralstart switch. Reconnect neutral start switchleads 14A and 14B.

8. Disconnect the rotary switch lead 14A andwith rotary switch in “START” check forbattery voltage at terminal S. If voltage ispresent, repair body wiring harness fromrotary switch to neutral start switch.

9. Disconnect lead 11A at the rotary switch,check lead 11A for battery voltage. If voltageis present, replace rotary switch.

10. Disconnect negative battery cable frombattery and disconnect protective controlbox connector plugs from protective controlbox. Reconnect negative battery cable tobattery. Check pin E of engine wiringharness connector plug for battery voltage.If voltage is present, check for continuityfrom pin G on the control box wiring harnessconnector plug to lead 11A of rotary switch.If continuity is present, replace protectivecontrol box. If no continuity is present,repair body wiring harness.

3


C. BATTERY CIRCUIT CHECKS(Figure 12-2)

1. Check batteries for loose or dirtyconnections.

a. Make sure all connection are clean andtight. This includes the interconnectcables, clamp, shunt, power stud andthe slave connector. Also check wire 6Aand 7A under vehicle where they enterthe shunt.

2. Check batteries fluid level.

a. There is a ring inside the battery fillplugs. The water level should be at thering.

Figure 12-2. Battery Fill Rings.

3. Check batteries voltage for 23.5 to 25.5volts.

a. If batteries voltage is low, check eachbattery individually. Voltage should bebetween 11to13 volts. (A good batteryhas 12 volts at 70°F (22°C).

b. If battery is below 11-13 volts, rechargebattery.

c. If batteries are good, check the voltagedrop across cables in battery box. Voltagedrop should be less than 0.25 voltsmaximum.

4. Load test batteries. If batteries fail loadtest, replace batteries.

Check starter voltage drop from power stud of6A to starter ground.Voltage drop should beless than 0.25 volts. If voltage drop is more than0.25 volts replace 6A cable.


Page 12-4

D. 6.2L ENGINE GLOW PLUGSYSTEM (Figure 12-3 through 12-6)

The glow plug is basically an electric heaterthat is energized by the operator through theignition switch. Once energized, electric currentflows through the glow plug to cause it to glowor become red hot 1550°F to1650°F (829° to884°C). After a given time period when thestarter motor is engaged, the ambient air thatflows into the engine will be rapidly increasedin temperature through the use of the hot glowplug within the combustion chamber.

Each cylinder in the 6.2L engine employs aglow plug that is actually a 12-volt unit operatedfrom the 24-volt battery system when the ignitionkey is turned to the run position prior to engagingthe starter motor. They remain pulsing for ashort time after starting, then automatically turnoff.

Within the instrument panel of the vehicle is a“glow plugs” light that will turn on immediatelywhen the ignition switch is turned to the runposition.

The major components of the glow plug systemare described in the following paragraphs.

GLOW PLUG


GLOW PLUGCONTROLLER

FUELSOLENOID

COLDADVANCESOLENOID

COLDADVANCESWITCH

PROTECTIVECONTROL BOX


WAIT TO STARTLAMP

ROTARYSWITCH

CIRCUITBREAKER #2

571A

27F

29D570A

459B

573A

54A

569A 569G

569C

2

6

1

3

4

5

A

F

H

B

C

D B

G

E

11A29A 29B

5B

583A

BR93A

A C D E

GHJK

29C

Figure 12-3. Glow Plug Controller Testing

5


(MALFUNCTION)

a. Glow Plug System Continues To CycleAfter Engine Is Warmed Up

Start engine, and check for 12-14 volts DC signalat alternator lead 2A. If no voltage is present orvoltage is not within limits, replace the alternator.If 12-14 volts DC is present, replace protectivecontrol box.

b. Using multimeter, check glow pluginternal resistance (Figure 12-5)

Connect one test lead to terminal (1) and othertest lead to threaded area (2).

Glow plug internal resistance should be 1.5-5.0ohms. If resistance is not 1.5-5.0 ohms, replaceglow plug.

Figure 12-4. HMMWV Glow Plug.

NOTE

• The following will explain proper operationof glow plug system. When engine is below120°F (48°C) and rotary switch is positionedto “RUN”, “Wait-To-Start” lamplight thengoes on for up to fifteen seconds, dependingon engine temperature, then goes off, enginecan then be started. After engine is started,glow plugs will continue to cycle (for up to 5minutes) then stop cycling.

• Glow plug system is cycling normal whenthere is an on pulse for approximately1 second and an off pulse for approximately15 seconds.

• To detect glow plug system cycling, watchvoltmeter. The gage needle will move to theleft when glow plugs are on, then return tonormal position when glow plugs are off. Arelay click should be heard from the protectivecontrol box as the system switches on andoff. Multimeter may be used on any glow plugwire to visually watch operation of glow plugsystem.

• If engine temperature is above 120°F (48°C),glow plugs are not required to start engine.

• Each glow plug draws approximately 11.25amperes. To test system connect AMP meteracross batteries. With glow plugs cycling,there should be approximately 90 amperedraw. Each bad glow plug will lower amperedraw approximately 11.25 amperes. (Example)With one bad glow plug, reading will beapproximately 78.75 amperes. With two badglow plugs, reading will be approximately67.5 amperes etc.

NOTE

Allow engine to cool for 30 minutes beforeperforming glow plug resistance checks.

1. Remove engine wiring harness connectorsfrom all glow plugs. Using a multimeter, checkglow plug resistance. Replace any glow plugnot having 1.5-5.0 ohms resistance.

NOTE

Allow engine to cool 2-3 hours beforeperforming glow plug controller resistancechecks if continuous controller cycling issuspected.

NOTE

If solid state glow plug controller is beingused, no test is available to test thecontroller. Replace if suspected of beingfaulty. If symptoms still exist, continuewith step 3.


Page 12-6

Refer to Figure 12-6 for the following steps.

2. Disconnect engine wiring harnessconnector from glow plug controller. Checkthe controller connector for dirt or moisturecontamination, clean if required. Usingmultimeter, check controller for thefollowing:

a. Check for continuity between pin 2 and pin6 (continuity should exist).

b. Check resistance between pin 2 and pin 3.The resistance should be approximately0.5 ohms.

c. Check resistance between pin 4 and pin 5.The resistance should be 24-30 ohms.

d. Check resistance between pin 1 and pin 5.The resistance should be 117-143 ohms.

NOTCH

PINS 2 & 6

PINS 2 & 3

PINS 4 & 5

PINS 1 & 5

CONTINUITY

0.5 OHMS

24–30 OHMS

117 – 143 OHMS

PIN CONFIGURATION

1

4

6

5

2

3

Figure 12-5. Glow Plug Controller

If any of the above conditions are not met,replace glow plug controller.

Refer to Figure 12-7 for the following steps.

3. Using a multimeter, check for continuitybetween terminal 5 at glow plug controller

connector (lead 93A) and ground. Repairengine wiring harness if continuity is notpresent.

WARNING

Negative battery cable must bedisconnected before disconnecting anyharness from protective control box.Failure to do so may result in injury topersonnel or damage to equipment.

NOTCH

1

4

TERMINAL 2 IS BLANK6

5

2

3

Figure 12-6. Glow Plug ControllerContinuity Test.

4. Disconnect negative battery cable anddisconnect engine wiring harness connectorat protective control box. Inspect the controlbox and harness connector for dirt, ormoisture contamination, clean if required.Using a multimeter, check for continuitybetween terminal “D” in protective controlbox engine wiring harness connector andeight glow plug connectors (leads 575).Repair engine harness, if any glow plugleads do not have continuity.

5. Using a multimeter, check for continuitybetween terminal “G” in engine wiringharness connector at protective control boxand lead 2A at alternator. Repair enginewiring harness, if continuity is not present.

7


6. Using a multimeter, the following continuitychecks must be made from engine wiringharness connector at protective controlbox to engine wiring harness connector atglow plug controller.

a. Terminal “C” at protective control boxconnector to terminal 4 at glow plugcontroller connector (lead 370A).

b. Terminal “B” at protective control boxconnector to terminal 3 at glow plugcontroller connector (lead 459B).

c. Terminal “H” at protective control boxconnector to terminal 1 at glow plugcontroller connector (lead 573A).

d. Terminal “A” at protective control boxconnector (lead 54B) to terminal 6 atglow plug controller connector (lead583A).

If any leads did not have continuity, repairengine wiring harness.

7. If no problem is found in glow plugs, glowplug controller or engine wiring harness,replace protective control box and checksystem for proper operation.

END OF TESTING!

E. COLD START ADVANCE DOES NOTFUNCTION PROPERLY

1. Remove engine access cover. Disconnectleads 569A and 569B from cold advanceswitch. Using multimeter, check for batteryvoltage at lead 569A with rotary switch in“RUN” position. If battery voltage is notpresent, repair engine wiring harness.

2. Disconnect lead 569B from fuel injectionpump. Using multimeter, check forcontinuity through lead 569B from injectionpump to cold advance switch. If continuityis not present, repair engine wiring harness.

3. Using multimeter, check for continuitythrough cold advance switch with enginetemperature below 70°F (21°C). If continuityis not present, replace cold advance switch.Check for continuity through cold advanceswitch with engine temperature above l00°F(38°C). If continuity is present, replace coldadvance switch.


Page 12-8

F. NEIHOFF 100 AMP ALTERNATORTESTING (Figure 12-7 through 12-9.

a. On Vehicle Test

The alternator is examined most easily on thevehicle, where the charging and ignitionsystems of the vehicle can be examined at thesame time.

Equipment:

Belt Tension GaugeVoltmeter, 0-40 Volt RangeAmmeter, 0-400 Amp Range

b. Preliminary Checks

1. Check Belt Tension. Use Belt TensionGauge to measure belt tension within rangefor the appropriate belting system: DualBelt: 80-120 lbs each belt.

2. Check Battery. Battery must be in goodcondition and fully charged. If condition ismarginal the battery should be replacedwith one which is known to be in goodcondition.

3. Check Electrical Connections inCharging Circuit. Make sure allconnections are clean, tight, and free ofcorrosion. Battery connections areespecially important.

4. Check Ignition Circuit. If alternator is notcharging, check for voltage at the alternatorenergize terminal (Red Terminal). Refer toFigure 12-7 for energize terminal locationon the outside of the regulator. Look for24V nominal.

RED TERMINAL(ENERGIZE)

LOCKNUT #10-24 TORQUETO 2 N•m/25 lb-in

WASHER

NUT 1/4-20 TORQUE TO 3 N•m/25 lb-in

WASHER

IGNITION LEAD (568)AND BOOTS (3 PLACES) TO BE SUPPLIED WITH ALTERNATOR

REF VEHICLEHARNESS

YELLOW TERMINAL (AC)

5A

568

2A

568A

Figure 12-7.Regulator AC and Energize Terminals

9


c. Test Setup

1. Discharge Battery as Follows:

1. Remove wire 54A from injection pump.

2. Turn all lights and accessories. Crankthe engine for 10-15 seconds todischarge battery, then stop crankingengine.

3. Turn all lights and accessories off.

4. Reconnect wire 54A to injection pump.

2. Attach meter as indicated by Figure12-8A. Be sure to measure voltage andamperage at alternator, not battery orintermediate point.

If an in-line ammeter is used, disconnect batteryground cable before connecting ammeter. Thenreconnect battery ground cable. Ammeterconnections must carry rated output ofalternator.

– + –+

AMMETER VOLTMETER

BATTERY

A BYELLOW TERMINAL (AC)

RED TERMINAL(ENERGIZE)

B+ NEG

Figure 12-8.On Vehicle Test.


Page 12-10

d. Test Procedure

1. Start engine. Accelerate to high idle.Caution: If voltmeter reading exceeds30.5V, stop engine immediately and referto Table 1-1.

2. Watch meter reading. If battery issufficiently discharged, amps should be

“high”. Volts should be within or below the“normal range” of Table 1-2, as batteryapproaches full charge, amps should fallas volts rise. When amps and volts stabilize,note readings and refer to Table 1-1.

11


NOTE:Regulator set at 28.2 ±.5 volts at 72°F and compensate fortemperature variation of –0.1 volt per 10°F.

e. Static Checks: Partially DisassembledAlternator

Static Tests are performed on the partiallydisassembled alternator to confirm componentfailure indicated by On-Vehicle Test and BenchTests

1. Equipment: Ohmmeter, Simpson 260or equivalent Regulator Tester, Zetronor equivalent, or Ohmmeter Diode Testeror Ohmmeter.

2. Remove the pulley (refer to DisassemblyProcedure).

Disconnect all phase leads attached to theheatsink (“P1” through “P6”) in Figure 12-9.Disconnect alternator connector fromvoltage regulator.

Before repairing the alternator, perform ALLStatic Tests.

f. Field Coil Test

1. Remove both field coil (F+, F-) leads fromterminal studs on the front housing. (SeeFigure 12-9).

2. Check for open field coil. Set ohmmeter tox1 scale and make sure meter is zeroed.Connect ohmmeter leads to each of thetwo field leads and measure the resistance.Ohmmeter should read less than 3 ohms.If ohmmeter reads above the specifiedlimit, the field coil is open and must bereplaced (replace or repair stator, shellassembly or alternator).

3. Check for grounded field coil. Setohmmeter to x10k scale and make sureohmmeter is zeroed. Connect oneohmmeter lead to either field lead, connectthe other ohmmeter lead to the fronthousing ground stud. The ohmmetershould read very high. If the ohmmeterreads less than 100k ohm the field coil isgrounded and must be replaced (replaceor repair stator, shell assembly oralternator).

4. Replace both field coil (F+, F–) leadsbefore performing electrical continuitycheck.


Page 12-12

g. Electrical Continuity Check

NoteMake sure coil (F+, F–) leads are

connected to terminal studs.

1. Set ohmmeter to x10 scale and makesure meter is zeroed.

2. Probe the alternator connector pins toinsure all internal wiring is intact. (Referto figure 12-9, page 14).

h. Diode Heatsink Tests

Remove all phase leads (P1-P6) from fronthousing (refer to figure 12-9 page 14).Note: Do not allow sleeving on leads to slidedown leads; phase terminals without sleevescan short to alternator body.

The diode heatsink assembly is normally checkedusing a diode tester. If a diode tester is used, referto manufacturer’s instructions for properconnections. When a diode tester is not available,use an ohmmeter and refer to the followingprocedure. Note: Do not use an AC device, suchas a leakage tester to check the diode heatsink.

1. Check positive diodes (Refer to Figure12-9, page 14). Set ohmmeter to x 100scale and make sure ohmmeter iszeroed. Connect one ohmmeter lead tothe B+ output connector. Connect theother ohmmeter lead to each of the sixheatsink phase terminals “S”. All sixreadings should be nearly alike; eitherless than 600 ohms, or very high. If allsix readings are not alike, the dioderectifier assembly is defective and theheatsink assembly or front housingassembly must be replaced.

13


Reverse ohmmeter leads, and againobserve resistance between the “B+”stud of the output connector and eachof the six heatsink terminals “S”. All sixreadings should be nearly alike, andopposite the readings obtainedpreviously; if all readings were less than600 ohms before, all readings shouldbe very high now, and vice versa. If anyreading is not alike the diode rectifierassembly is defective and the heatsinkassembly must be replaced.

2. Check negative diodes (Refer to Figure12-9). Set ohmmeter to x100 scale andmake sure ohmmeter is zeroed.Connect ohmmeter lead to the groundterminal located on the outside of thefront housing, connect the otherohmmeter lead to each of the sixheatsink phase terminals “S”. All sixreadings should be nearly alike; eitherless than 600 ohms, or very high. If allsix readings are not alike, the dioderectifier assembly is defective and theheatsink assembly is defective, and theheatsink assembly or front housingassembly must be replaced.

Reverse ohmmeter leads, and againobserve resistance between groundterminal and each of the six heatsinkphase terminals “S”. All six readingsshould be nearly alike, and opposite thereadings obtained previously; if allreadings were between less than 600ohms before, all readings should bevery high now, and vice versa. If anyreading is not alike, the diode rectifierassembly is defective and the heatsinkassembly or front housing assemblymust be replaced.

NOTE

Heatsink diodes are derated for heavyduty performance. If diode failure isdetected the entire charging systemshould be examined for looseconnections (especially battery). If diodefailure is indicated, stator failure must besuspected.

i . Stator Tests

The alternator has two separate statorassemblies that will be checked individually.Make sure that all phase leads are disconnectedfrom the heatsink (Refer to Figure 12-9).

1. Check front stator. Set ohmmeter to x1scale and make sure ohmmeter is zeroed.Check for open stator windings byconnecting ohmmeter between eachsuccessive pair of stator phase leads (Referto Figure 12-9), (“P1”-”P2", “P2”-”P3", and“P1”-”P3"). Note it may be necessary toprobe under the sleeves of the phase leadsin order to make electrical contact.Ohmmeter should read less than 1 ohmbetween each pair of stator phase windings.If ohmmeter reads very high (infinity) thestator is open and must be replaced (replaceor repair stator and shell assembly).

Set ohmmeter to x10k scale and make sureohmmeter is zeroed. Check for shortedstator windings by connecting ohmmeterbetween each phase lead (“P1”, “P2”, and“P3”) and the ground terminal located onthe outside of the front housing. Ohmmetershould read very high (infinity). If ohmmeterreads zero the stator is grounded and mustbe replaced (replace or repair stator andshell assembly).


Page 12-14

Set ohmmeter to x10k scale and make sureohmmeter is zeroed. Check for shorted statorwindings by connecting ohmmeter betweeneach phase lead (“P4”, “P5”, and “P6”) and theground terminal located on the outside of thefront housing. Ohmmeter should read very

high. If ohmmeter reads zero the stator isgrounded and must be replaced (replace orrepair stator and shell assembly).

NOTE:Disassemble alternator only as far asnecessary to replace defective part.

Figure 12-9.

15


G. PROTECTIVE CONTROL BOXTESTING (Figure 12-10)

WARNING

Negative battery cable must bedisconnected before removing anyconnector from the protective controlbox, or injury to personnel or damage toequipment may result.

NOTE

During continuity check of pin “A” andpin “G” at the body harness connector,the ignition switch must be in the“START” position.

1. Disconnect body harness connector andengine harness connector from protectivecontrol box. Check for continuity betweenpin “A” and “G” on the body harness

connector. Continuity should be between0.1–0.3 ohms. If the incorrect reading isfound go to step 2. If the correct reading isfound, go to step 3.

2. Disconnect lead 14B from the neutral startswitch. Check for battery voltage at neutralstart switch lead 14 with rotary switch in“START”. If battery voltage is present,disconnect the negative battery cable frombattery, both cannon plugs from protectivecontrol box and lead 74A from starter.Ground lead 74A and check pin I on theengine wiring harness cannon plug for thecontrol box. If continuity is present, checklead 14B on neutral start switch to pin A onthe body wiring harness cannon plug forthe control box. If continuity is present,replace the control box. If no continuity ispresent, repair wiring harnesses. Reconnect

A I

EG

B

S




BLOCK

SHUNT

BATTERY12V

BATTERY12V


14B

14A

74A

81A

14B

6A

7A

11A ROTARYSWITCH

STARTER MOTOR

–

+

–

+

NEUTRAL STARTSWITCH


Figure 12-10. Starting System Schematic–Protective Control Box Testing.


Page 12-16

protective control box cannon plugs, neutralstart switch lead 14B, starter lead 74A tostarter, and negative battery cable tobattery.

3. Disconnect negative battery cable frombattery and disconnect protective controlbox cannon plugs from protective control

box. Reconnect negative battery cable tobattery. Check pin E of engine wiringharness cannon plug for battery voltage. Ifvoltage is present, check for continuityfrom pin G on control box body wiringcannon plug to lead 11A of rotary switch. Ifcontinuity is present, replace protectivecontrol box. If no continuity is present,repair body wiring harness.

Figure 12-10. Starting System Schematic–Protective Control Box Testing.

A I

EG

B

S




BLOCK

SHUNT

BATTERY12V

BATTERY12V


14B

14A

74A

81A

14B

6A

7A

11A ROTARYSWITCH

STARTER MOTOR

–

+

–

+

NEUTRAL STARTSWITCH


17


H. LIGHT TESTING

1. Disconnect body wiring harness from lightswitch. Using multimeter, check for batteryvoltage at terminal “F” in body wiringharness connector. If battery voltage is notpresent, repair body wiring harness. Ifwiring harness cannot be repaired, replacethe wiring harness.

2. Working from Table 12-8, Lighting CircuitChart, connect a jumper wire from terminal“F” to circuit terminal being tested. If lamps

light with jumper wire connected, replacemain light switch. If lamps do not light,repair or replace hood wiring harness (frontlights only), or repair body wiring harness.

3. Working from Table 12-9 light switchcontinuity chart, position light switch controllevers to position indicated for circuit functionbeing tested. Check for continuity betweenlight switch connector pins as shown. Ifcontinuity is not present at the appropriatelight switch connector pins, replace mainlight switch.

CIRCUIT CHART

PIN WIRE NO. CIRCUIT

B 40A Panel Lights

C 22A Directional Control (Service Stoplight)

D 19A B. O. Driving Light

E 20-24A B. O. Marker Lights

F 15A Battery Pos. 24 Volts

H 21A-491A Service Rear & Parking Lights

J 46C-461A Directional Indicator

M 16A Service Headlights

N 23A B. O. Stoplight

Table 12-8. Lighting Circuit Chart


Page 12-18

LIGHT SWITCH CONTINUITY CHART

CIRCUIT FUNCTION LIGHT SWITCH CONTINUITYBEING TESTED LEVER POSITION CHECK PINS

Off Check all pins (pin to pin) for infinity

Switch Park A to B, H to L

Switch Dim A to B, H to M

Switch Panel Bright A to B, H to M

Service Stoplights Stoplights A to F, C to K

Directional Indicators(turn signals) Service Drive F to H

Parking, Tail, andSide Marker Lights Service Drive F to H

Panel Lights Service Drive F to B(panel lights bright)

Headlights Service Drive F to M(panel lights bright)

Front and RearBlackout Marker Blackout Marker F to E

Blackout Stoplamps Blackout Marker F to A, K to N

Blackout Headlamps Blackout Drive F to D

Table 12-9. Light Switch Circuit Chart.

19


I. HIGH BEAM SELECTOR SWITCHTESTING (Figure 12-12)

Remove high beam selector switch and checkfor battery voltage at lead 16A. If voltage ispresent, check high beam selector switch forcontinuity between leads 16 and 17 in high

position, and leads 16 and 18 in low position.If continuity is not present in either positionwhen selected, replace high beam selectorswitch.

END OF TESTING!

Figure 12-12. Master Lightswitch Pin Configuration.


Page 12-20

J. STOPLIGHTS INOPERATIVE OR DONOT OPERATE PROPERLY(Figure 12-13)

1. Check stoplight switch adjustment. Adjuststoplight switch.

2. Disconnect leads 75A and 75B fromstoplight switch. Using multimeter, checkleads on stoplight switch for continuitywhile operating switch. If continuity is notpresent, replace stoplight switch.

3. Check body wiring harness light switchcannon plug pins A to K for continuity whileoperating stoplight switch. If no continuityis present, repair body wiring harness.

END OF TESTING!

K . TURN SIGNALS INOPERATIVE ORDO NOT OPERATE PROPERLY(Figure 12-13 and 12-14)

1. Disconnect negative battery cable andbody wiring harness connection from turnsignal switch. Using multimeter, checkcontinuity of leads 467A and 467B fromthe body harness light switch connectorpin J to body harness turn signal switchconnector pin G. If continuity is not present,repair body wiring harness.

Figure 12-13. Turn Signal System Schematic.

A B C

E F

F C J

A E D C B G F H

RIGHT FRONTTURN SIGNAL

PROTECTIVECONTROL BOX



LIGHT SWITCH T/SIGNALHAZARDFLASHER

RIGHT REARTURN SIGNAL

LEFT FRONTTURN SIGNAL

LEFT REARTURN SIGNAL

TURN SIGNALSWITCH

HOOD HARNESSCONNECTOR

F

G

57K

15A

81A

22-460C

325B

325A

22-460C

467A

467B

22A

460B

461B

461A

22-461A

22-461B

21


Refer to Figure 12-14 for the following step.

2. Using multimeter, check continuity of turnsignal switch from pin G to pin F with turnsignal switch in left, right and hazardpositions. If continuity is not present,replace turn signal switch.

3. Disconnect wiring harness from turn signalflasher. Using multimeter, check forcontinuity between lead 57K (terminal C)and ground. If continuity is not present,repair body wiring harness.

4. Set control lever in left hand or right handpositions. Using multimeter, check forbattery voltage at lead 325B in turn signalflasher harness connector. If battery voltageis present, connect a jumper from lead325A (terminal A) to lead 325B (terminal B)in flasher harness connector, if turn signallamps light, replace flasher.

5. Disconnect wiring harness from directionalsignal control. Remove indicator lamp fromcontrol unit. Using multimeter, test forcontinuity using Table 12-3 Control UnitTest Chart. If any circuit does not test asshown on chart, replace directional signalcontrol.

Figure 12-14. Turn Signal Pin Configuration.


Page 12-22

HHHHDDF

ABCECEG

OPENOPENOPENOPENSHORTEDSHORTEDOPEN

FHHHHDD

GAEBCCE

SHORTEDSHORTEDSHORTEDOPENOPENSHORTEDOPEN

HHHHFDD

BCAEGEC

SHORTEDSHORTEDOPENOPENSHORTEDSHORTEDOPEN

HHHHDDF

ABCEECG

SHORTEDSHORTEDSHORTEDSHORTEDSHORTEDSHORTEDSHORTED

A. DIRECTIONAL SIGNAL CONTROL LEVER IN “NEUTRAL” POSITION

B. DIRECTIONAL SIGNAL CONTROL LEVER IN “LEFT TURN” POSITION

FROM PIN TO PIN CONTINUITYINDICATION




C. DIRECTIONAL SIGNAL CONTROL LEVER IN “RIGHT TURN” POSITION

D. DIRECTIONAL SIGNAL CONTROL LEVER IN “HAZARD WARNING” POSITION

CONTROL UNIT TEST CHART

Table 12-10. Control Unit Test Chart.

5. Position main light switch lever to stoplight position. Working from Table 12-4 circuit chart,connect a jumper wire (minimum 14 AWG) from pin G of the turn signal switch body harnessconnector to theappropriate pin of the circuit being tested. If lamps do not light, repair orreplace hood wiring harness.

CIRCUIT CHART


A 460A Right Front Turn Signal

B 461A Left Front Turn Signal

C 22-461A Left Rear Turn Signal

E 22-460A Rear Rear Turn Signal

Table 12-11. Circuit Chart.

23


2. Using multimeter, check for continuitybetween pins D and L of trailer receptacleto frame. If continuity is not present, repairbody wiring harness.

3. Position light switch in circuit being tested.Using multimeter, connect ground lead toterminal L in trailer receptacle. Using Table12-12 (page 12-26) Trailer ReceptacleCircuit Chart, connect positive lead frommultimeter to circuit terminal in trailerreceptacle being tested. If battery voltageis present, repair trailer wiring harness. Ifbattery voltage is not present, repair bodywiring harness.

L. ONE OR MORE TRAILER LIGHTSINOPERATIVE (VEHICLE LIGHTINGSYSTEM FUNCTIONS NORMALLY)(Figure 12-15)

1. Position light switch to circuit being tested.Check for battery voltage at sockets. Ifbattery voltage is present, replace bulbwith bulb known to be operative. If bulbdoes not light, check for corrodedconnections, loose lamp sockets, ordamaged wire terminals, repair or replaceany damaged components.

A

B

C

D

E

F

H

J

K

L

M

N

24E

22-461C

24D

90B

21D

23C

24F

22-460B

90A

TRAILER RECPTICLE

BODY HARNESS

B/O TAIL LAMP

LEFT SERVICE T/SIGNALAND STOP LAMP

B/O TAIL LAMP

GROUND

SERVICE TAIL LAMP

B/O STOP LAMP

B/O TAIL LAMP

RIGHT SERVICE T/SIGNAL AND STOP LAMP

GROUND

Figure 12-15. Trailer Lighting System Schematic.


Page 12-24

TRAILER RECEPAICLE CIRCUIT CHART


A 24E Rear B.O. Marker (LH)

B 22-461A Service Stoplight (LH)

C 24D Rear B.O. Marker (RH)

D 90B Ground to Frame

E 21D Service Taillight

F 23C B.O. Stoplight

H 24F B.O. Marker Lights

J 22-460B Service Stoplight (RH)

K None Not Used

L 90A Ground to Frame

M None Not Used

N None Not Used

Table 12-12. Trailer Receptacle Circuit Chart

25


M. WARN 6000 POUND , 24 VDC WINCHELECTRICAL TROUBLESHOOTINGPROCEDURES

a. Power Supply

Check for tight fit of all connections and use avolt meter to verify battery voltage at the busbar connecting solenoids #1 and #3 (Figure12-16). Connect black test lead to ground andred test lead to the hot bus bar, (100 ampsminimum required for testing , 200 ampsminimum required for operation).

Note

The black insulating coating cansometimes contaminate electricalterminals and may need to be scrapedoff of contact surfaces.

b. Grounding

The Solenoid mounting plate should begrounded to the motor by means of a bandclamp. Newer model winches will also have aground wire connecting the mounting plate withthe motor ground bolt (-). Use an ohm meter tomeasure resistance between the mounting plateand the motor case; resistance should be lessthan 1 (ohm).

Figure 12-16. Winch Testing.

BLACK

RED LEADOF E.C.L.

TO POSITIVE (+)BATTERY

TERMINAL

GREEN LEADOF E.C.L.

BLACK TOMOTOR

ARMATURE

BLACK TOMOTOR

FIELD NO.2

BROWN TO MOTORFIELD NO.1

BLACK

E.C.L.(ELECTRONIC

CURRENT LIMITER) INSULATEDSPLICE

BUS BAR“HOT”

THERMALTEMPERATURE

SWITCH

619 GREEN TO E.C.L.

472 GREENTO REMOTE

CONTROL UNIT

TO REMOTECONTROL

UNIT473 BLACK471 WHITE

1 2

3 4


Page 12-26

c. Electronic Current Liiter (ECL)

Note

The ECL can be tripped when firstpowered ‘on’ so always reset bypowering out the wirerope for ten (10)seconds to reset the limiter.

1. If the winch will power-out but will notpower-in, the ECL may be defective. First,check that the red wire coming from thecharged bus bar is connected properly andthat the mounting L-bracket of the ECL

circuit board is cleanly grounded to thesolenoid plate.

1. If still no power-in, by-pass the ECL asfollows: Cut the green ,(#619 ) wire comingfrom the thermal switch to the ECL near thesplice on the ECL side (Figure 12-16).Take the cut wire coming from the thermalswitch and connect it to solenoid #4 on thesame terminal that the green ECL wire isattached (Figure 12-16). The winch shouldoperate in both directions. If not, continuewith the troubleshooting steps.

Figure 12-16 Repeat. Winch Testing.

BLACK

RED LEADOF E.C.L.

TO POSITIVE (+)BATTERY

TERMINAL

GREEN LEADOF E.C.L.

BLACK TOMOTOR

ARMATURE

BLACK TOMOTOR

FIELD NO.2

BROWN TO MOTORFIELD NO.1

BLACK

E.C.L.(ELECTRONIC

CURRENT LIMITER) INSULATEDSPLICE

BUS BAR“HOT”

THERMALTEMPERATURE

SWITCH

619 GREEN TO E.C.L.

472 GREENTO REMOTE

CONTROL UNIT

TO REMOTECONTROL

UNIT473 BLACK471 WHITE

1 2

3 4

27


d. Thermal Switch

Note

The motor will not run if the thermalswitch is open or if its terminals are incontact with the motor case. The switchshould normally open when thetemperature at the motor brushesreaches 400+ F.

1. To check a faulting or shorting switch, usean ohm meter and measure the resistanceof the thermal switch between the wire cutin the previous step and the socket pin(#472) of the plug, which is connected tothe green wire (Figure 12-17). If the buttsplice and switch are good, the resistanceshould be less than 1 (ohm) across theswitch. If the switch is open at room

471WHT

472GRN

473BLK

1 2

A

4

FLO

F23

ARMATURE

YELLOW

GREEN

CURRENT SENSE

POWER-IN ECL OUT

POWER-IN ECL IN

ECL

BLACK NO. 473

WHITE NO. 471

24 VDC

INSULATEDSPLICE

BROWN

GREEN NO. 472

BLK

WHT

GRN

TO REMOTECONTROL

PLUG

GREEN NO. 619

THERMALTEMPERATURE

SWITCH

Figure 12-17Figure 12-17.Repeat. Winch Testing.


Page 12-28

temperature then the motor should bereplaced. Next, check the resistancebetween the cut wire and the bare motorcase. The resistance should be greaterthan one megaohm. If not, replace motor.

e. MotorNote

If the motor is suspected to be failingcheck the following.

Disconnect F1, F2 and A leads from motor.

Measure the resistance from‘F1’ and ‘F2’ andbetween ‘A’ and ground. Resistance should beless than 1 (ohm). The motor brushes couldbe worn, or the internal wiring could be burnedand the motor should be replaced.

Note

If faults were not detected in steps A, B,C, D and E, replace solenoid pack.

Figure 12-17.Repeat. Winch Testing.

471WHT

472GRN

473BLK

1 2

A

4

FLO

F23

ARMATURE

YELLOW

GREEN

CURRENT SENSE

POWER-IN ECL OUT

POWER-IN ECL IN

ECL

BLACK NO. 473

WHITE NO. 471

24 VDC

INSULATEDSPLICE

BROWN

GREEN NO. 472

BLK

WHT

GRN

TO REMOTECONTROL

PLUG

GREEN NO. 619

THERMALTEMPERATURE

SWITCH

1

Section 13. Time Delay Module Operation

SECTION 13TIME DELAY MODULE

OPERATION

PICTORIAL SCHEMATICS

NOTE

The following group of pictorial schematics are intended to bepresented by a qualified instructor who is familiar with theTime Delay System and can properly color-code current andfluid flow.


Page 13-2

A. TIME DELAY MODULE OPERATION(Figure 13-1).

a. Fan Temperature Switch ClosedEngine Not Running (Figure 13-1)

With the rotary ignition switch (1) in the off position (open) there is no current flow to the fantemperature switch (2) or the time delay module (3) through the #458 wire. Since the electricsolenoid (4) is not activated, there is no hydraulic flow through the hydraulic control valve (5)to release the fan clutch. The fan clutch remains engaged, locking the fan to the fan driveunit.

Figure 13-1. Fan Temperature Switch Closed Engine Not Running.

583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH

FAN TEMPERATURESWITCH

N.C.

ROTARYSWITCH

OFF

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

N.O.

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLUID

3


583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH


N.C.

ROTARYSWITCH

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

R

N.O.

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLOW

Figure 13-2. Fan Temperature Switch Closed,Engine Temperature below 230°F.

Engine Running.

b. Fan Temperature Switch Closed,Engine Temperature below 230 °F.Engine Running. (Figure 13-2)

1. With the rotary ignition switch (1) in the “R” (run position), current flowsfrom the battery through the #458 wire across the normallyclosed (NC) fan temperature switch (2), through a relay (6), out the #98wire to ground.

2. The current flowing through the relay (6) closes a set of points in the #93circuit. This circuit completion now allows current to flow through the#583/569 wire, through the time delay module (3), out the time delaymodule via the #583/458 wire, through the fan solenoid (4), out the #93wire, back through the time delay module (3), across the closed points (6)and out to ground.

3. This flow of current activates the fan solenoid (4), which opens the fanhydraulic control valve (5), allowing hydraulic oil to flow up to 160 PSI tothe fan clutch, overcoming the spring and disengaging the fan from thefan drive, letting the fan free spin.


Page 13-4

c. Fan Temperature Switch ClosedEngine Temperature Below 230 °F.(Figure 13-3)

1. When the engine temperature reaches 220°F, the normally closedfan temperature switch (2) opens. The open switch breaks thecompleted circuit through the relay (6) to the #93 ground wire.

2 . The points opening, break the completed #583/458 circuitthrough the fan solenoid (4) to ground.

3 . When the fan solenoid (4) is de-energized, the fan hydrauliccontrol valve (5) closes, blocking hydraulic fluid flow fromthe pump to the fan clutch, letting the fan clutch lock the fanto the fan drive for engine cooling.

Figure 13-3. Fan Temperature Switch ClosedEngine Temperature Below 230°F.

583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH


N.C.

ROTARYSWITCH

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

R

N.O.

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLUID

5


d. Fan Temperature Switch OpenEngine Temperature Above 230 °FKickdown Switch Closed (Figure 13-4)

1. Engine temperature is above 220°F and the fan clutch is engaged, turning thefan for engine cooling.

2. When extra horsepower is required, the kickdown switch (7) is activated,completing the #315 circuit. Current flows from the batteries through the #458wire, through the #315 wire, across the closed kickdown switch (7), through thenormally open 20 second timer (8) and out the #93 wire to ground.

3. The 20 second timer closes the points (9) in the #93 circuit, letting current flowthrough the #583/458 circuit to the fan solenoid (4) through the #93 wire, acrossthe closed points (9) and out to ground.

4. This flow of current through the fan solenoid (4) opens the control valve (5) andholds it open as long as the timer (8) is activated. This allows oil to flow to thefan clutch, overriding the spring pressure, disengaging the fan clutch andgiving the engine an approximate 12-15 horsepower boost.

Figure 13-4. Fan Temperature Switch OpenEngine Temperature Above 230°F

Kickdown Switch Closed.

583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH


N.C.

ROTARYSWITCH

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

R

N.O.

g

h

i

KICKDOWN SWITCHN.O.

N.O.20 SecTIME

315315

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLUID


Page 13-6


Kickdown Switch Closed.

583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH


N.C.

ROTARYSWITCH

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

R

N.O.

g

h

i

KICKDOWN SWITCHN.O.

20 SecTIME

CAPACITORj

k

315

N.C.

315

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLUID

e. Fan Temperature Switch OpenEngine Temperature Above 230 °FKickdown Switch Closed (Figure 13-5)

The first 20 second timer (8) actually operates a dual set of points(9) simultaneously. Current flows across the second set of points(9), into a capacitor (10), charging the capacitor.

7


f. Fan Temperature Switch OpenEngine Temperature Above 230 °FKickdown Switch Open (Figure 13-6)

1. After the first 20 second timer (8) expires, the dual points (9) open,breaking the completed #93 circuit and the fan clutch is engaged forextra engine cooling.

2. When the current to the capacitor (10) is interrupted, the capacitor (10)discharges its stored current through the second 20 second timer (11)and out the #93 wire to ground. This discharge of current activates the#2 timer (11), opening the points in the #93 circuit (12).

3. If the kickdown switch (7 ) is activated again (while the #2 timer is in its20 second cycle) the fan will not disengage. After the #2 timer completesits 20 second cycle, the kickdown switch (7) can be activated and the fanwill disengage again, giving the engine an additional gain in horsepower.

583

569

93

458

FAN SOLENOIDN.O.

FLUID FROMPUMP

FAN HYDRAULIC

CONTROLVALVE

FLUID TOFAN CLUTCH


N.C.

ROTARYSWITCH

583

458

93

a

b

c

d

e

OPEN @ 230°F (110°C)CLOSED @ 190°F (88°C)

f

TIME DELAY MODULE

R

N.O.

g

h

i

KICKDOWN SWITCHN.O.

20 SecTIME

CAPACITORj

k

315

N.C.

l

BATTERY CURRENT

POTENTIAL CURRENT

NO CURRENT FLOW

HYDRAULIC FLUID


Kickdown Switch Open.


Page 13-8

B. TIME DELAY MODULE TESTING

a. Description

The time delay module sends a delayedsignal to the fan clutch solenoid for delayof fan actuation to provide neededhorsepower for engine acceleration. Duringnormal engine operation [(engine coolanttemperature below 230°F) (110°C)],current flows through the time delay moduleenergizing the fan solenoid circuit Thisprovides hydraulic pressure to overcomespring pressure thereby disengaging thefan clutch.

When engine coolant temperature exceeds230° F(110°C), current is interrupted by the fantemperature switch. This interruption of currentcauses the time delay relay to open, therebyde-energizing the fan solenoid circuit andallowing the fan to engage for additional cooling.If the kickdown switch is actuated during fanoperation, the time delay is activated,disengaging the fan for approximately 20seconds and providing additionalhorsepower. If the kickdown switch isactivated again, an additional timer withinthe time delay module prevents thedisengagement of the fan until 20 secondshas elapsed allowing for adequate enginecooling. After the timer completes its 20 secondcycle, the kickdown switch can be reactivatedand the fan will disengage, providing additionalhorsepower.

9


b. On-Vehicle Testing (Figure 13-7)

1. Disconnect glow plug controller.

2. Turn rotary switch to the RUN position.

3. Using a multimeter, measure voltage at thefour and two prong connector of the timedelay module (do not disconnect prongs).

4. Perform continuity test on control valvesolenoid. 58 to 78 ohms both ways.

c. Four Prong Connector

a. Leads 458 and 569 should indicate batteryvoltage. If no voltage is present, repairignition circuit.

b. Leads 93 and 315 should indicate 0voltage. If voltage is indicated, repair liveshort.

d. Two Prong Connector

a. Lead 483 should indicate battery voltage.If no voltage is indicated, replace timedelay module.

b. Lead 93 should indicate 0 voltage. If batteryvoltage is indicated, replace time delaymodule.

3. Disconnect either lead (458) at fantemperature switch. [(This simulates enginecoolant temperature at 230°F (110°C) orabove)]. Using a multimeter, measure voltageat the four and two prong connectors. Leave458 disconnected.

a. Lead 458 at the four prong connectorshould measure 0 volts. Replace time delaymodule if voltage is indicated.

b. Lead 315 at the four prong connectorshould “momentarily” measure batteryvoltage when kick down switch is manuallyactuated. If measured voltage remains,replace time delay module.

c. Lead 93 at the two prong should measurebattery voltage with kickdown switch notengaged. Momentarily engage kickdownswitch, battery voltage should drop to 0for approximately 20 seconds. Ifmeasured voltage remains, replace timedelay module. Immediately after testactivate kickdown switch again. The timedelay switch should not allow the voltagedrop for another 20 seconds. After 20seconds has passed, repeat 1st test.

4. Turn rotary switch to the OFF position.

Figure 13-7. Time Delay Module Connector Testing.


Page 13-10

C. BENCH TESTING (Table 13-1)

NOTE

Time delay module may be bench testedwithout removing from vehicle.

1. Disconnect four and two prong leads frommodule.

2. Using a multimeter, check for continuity atthe following leads of the time delay module:

a. Lead 458 at the two prong and 569 at thefour prong. If continuity is not present,replace time delay module.

b. Measure for continuity in the remainingleads at the time delay module. Ifcontinuity is detected at any remainingleads, replace time delay module.

3. Using a multimeter, check for resistance atthe following leads. Set resistance rangeswitch at R3 (see Table 13-1).

TWO PRONG FOUR PRONG

LEAD # LEAD # RESISTANCE

9 3 + 458– ∞(Infinity)93– 458+ ∞9 3 + 569–/583* ∞93– 5 6 9 + / 5 8 3 * ∞9 3 + 93– ∞93– 9 3 + ∞9 3 + 315– ∞93– 315+ ∞458+/583* 458– ∞458–/583* 458+ ∞458+/583* 569–/583* Continuity458–/583* 569+/583* Continuity458+/583* 93– ∞458–/583* 93+ ∞458+/583* 315– ∞458–/583* 315+ ∞

* Wire #458 is superseded by wire #583, and #569 is superseded by#583 on Level III vehicles only.

Table 13-1. Time Delay Module Resistance Tests.

MILITARY HMMWV - FMTV Sales, LLC

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