T M 9 - 4 9 1 0 - 6 7 7 - 1 4 & P

TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORTAND GENERAL SUPPORT MAINTENANCE

MANUAL INCLUDING REPAIR PARTS LIST

FOR

TESTER, INTERNAL COMBUSTION ENGINEM O D E L 2 7 - 1 2

(CENTURY TOOL COMPANY, INC.)( N S N 4 9 1 0 - 0 0 - 2 5 5 - 8 6 7 3 )

H E A D Q U A R T E R S , D E P A R T M E N T O F T H E A R M Y

MAY 1980

TM 9-4910-677-14&P

Technical Manual HEADQUARTERSDEPARTMENT OF THE ARMY

No. 9-4910-677-14&P Washington, DC, 9 May 1 9 8 0

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORTAND GENERAL SUPPORT MAINTENANCE

MANUAL INCLUDING REPAIR PARTS LISTFOR

TESTER, INTERNAL COMBUSTION ENGINEMODEL 27-12

(CENTURY TOOL COMPANY, INC.)(NSN 4910-00-255-8673)

REPORTING OF ERRORS

You can help improve this manual by recommending improvements using, DAForm 2028 (Recommended Changes to Publications and Blank Forms) or D AForm 2028-2 located in the back of this manual. Mail your form direct toCommander, US Army Armament Materiel Readiness Command, A T T N :DRSAR-MAS, Rock Island, IL 61299. A reply will be furnished direct to you.

This manual is published for the purpose of identifying an authorized commercial manual for the use of

NOTE

the personnel to whom this tester - is issued.

Manufactured by: CENTURY TOOL COMPANY, INC.Hilton StreetEaston, PA 18042

Procured under Contract No: DAAA09-76-C-6699

This technical manual is an authenticat ion of the manufac tu re r s ’ commerc i a lliterature and does not conform with the format and content specified in AR 310-

3, Military Publications. This technical manual does, however, contain availableinformation that is essential to the operation and maintenance of the equipment.

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TM 9-4910-677-14 & P

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TM 9-4910-677-14 & P

TESTER, INTERNAL COMBUSTION ENGINE

The vacuum gauge is an accu-r a t e m e a n s o f a d j u s t i n g i g n i t i o nt iming . With the motor a t a fas tidle, advance the ignition timing soas to get the highest possible steadyreading on the vacuum gauge. N o wr e t a r d s o t h a t t h e n e e d l e o n t h egauge just begins to drop. Now theques t ion of de tona t ion or p i n ge n t e r s t h e p i c t u r e . If the cool ingsys tem is funct ioning proper ly , thespark plugs are not too hot, the com-bustion chamber is not insulated bya c a r b o n m i x t u r e , t h e c a r b u r e t o rm i x t u r e i s r i g h t , a n d t h e m i x t u r ef rom the carbure tor has the properturbulence in the combustion chain.ber, this is the proper timing posi-t i o n . U n f o r t u n a t e l y , i n m a n y i n -s t a n c e s , one or more of the abovement ioned condi t ions ex is t , and wemust set the ignition timing to com-pensate for them. To do this, shortout the cylinders by clipping the dif-ferent leads to the spark plugs untilthe motor i s work ing on two cy l -i n d e r s . W e a r e n o w a b l e t o d u p -l i c a t e a l o a d t e n d e n c y o f t h em o t o r t o d e t o n a t e o r p i n g . R e -tard the t iming t i l l the motor doesn o t p i n g , a n d t h e t i m i n g i s n o ws e t t o e l i m i n a t e d e t o n a t i o n .

Pairs of cyl inders can be placedunder load by shorting out the plugsof the other cylinders after openingthe throttle valve and locking it inp l a c e . If two cylinders are able torun the engine against the compres-sion of the others, it indicates thatthe ignition is not missing, that thec a r b u r e t o r h i g h s p e e d a n d p o w e rc i rcui t s a re working and tha t com-p r e s s i o n m u s t b e a t l e a s t i n f a i rcondition. Compare the vacuumreadings while running on differentpai rs of cyl inders .

O n 4 c y l i n d e r e n g i n e s , s e t t h ethrottle so the engine will run about900 RPM with all cylinders operating.Then run on the following pairs withthe other cylinders grounded out.

Run on cyl. 1 and 4. Run on cyl. 2 and 3

O n 6 c y l i n d e r e n g i n e s f i x t h ethrottle at about 1000 RPM with a l lc y l i n d e r s o p e r a t i n g Then run onthe following pairs with the remain-ing cylinders grounded out.

Run on cyl. 1 and 6 Run on cyl. 2 and 5

Run on cyl. 3 and 4

On 8 cy l inder - engines f ix thethrottle at about 1500 RPM runningon all cylinders. Then run on thefo l lowing pa i rs wi th the o ther cy l -inders grounded out.

Run on cyl. 1 and 8 Run on cyl. 3 and 6

Run on cyl. 2 and 7 Run on cyl. 4 and 5

T h e m a n u f a c t u r e r s o f V - 8 e n -g i n e s u s e s e v e r a l d i f f e r e n t m e t h o d so f n u m b e r i n g t h e c y l i n d e r s . T od e c r e a s e t h e c o n f u s i o n a l e t t e r i n gs y s t e m ( s e e i l l u s t r a t i o n ) h a s b e e nd e v e l o p e d

TM 9-4910-677-14 & P

which applies to all V-8 engines re-gardless of which cylinder the manu-facturer has designated as numberone. On V-8 engines, ground out allthe other cylinders and run on thefollowing pairs.

Run on cyl. A and F Run on cyl. D and G

Run on cyl. Band H Run on cyl. C and E

1. When the pointer is low butsteady, the trouble is somethingwhich affects all cylinders alike.This could be late ignition timing,late valve timing, or loose tappets.Such troubles can be responsible forthe reading being anywhere from1/4to 2 inches low. Intake system leaks(warped intake manifold, leakymanifold gasket, leaky carburetorflange gasket, poorly seating intakevalves and leaky intake guides) canbe responsible for the reading beinganywhere from 1/4 to 16 inches lowdepending on the size of the leak.

2. When the pointer pulses regu-larly, the trouble is something whichaffects one particular cylinder con-sistently; for instance, one exhaust,valve which does not seat, one ex-haust tappet which is too tight, orone sticky valve, or one dead sparkplug. The pulses of the pointer aremuch greater if they are caused bysome form of leakage such as ex-haust valve not seating, rather thansomething which, only slows the pis-tons such as a dead spark plug.

3. An unsteady pointer may becaused by defects occuring irregu-larly and in several or all of the cyl-inders. Other defects which areresponsible for an unsteady pointerare loose distributor governorsprings, rich carburetor mixture,extremely advanced or retardedspark, wide spark plug gaps, igni-tion points not synchronized, or in-take valves shifting on their seats.

4. It the pointer is unsteady and ifthe sweeps of the pointer increasewith increases in speed, the troubleis weak or broken valve springs. Ifthe sweeps get smaller but morerapid on increasing the speed, thetrouble is in intake system leaks. Ifthe pointer steadies on increasingspeed, the trouble is ignition, faultydistributor weights, or carburetion.

5. This is a normal reaction whenthe throttle valve is opened andclosed. If the pointer does not re-spond with wide sweeps, it is an in-dication that leakage exists. If thepossibilities of leakage throughpoor1y seating valves, manifolds,gaskets, etc. have been exhausted,then the piston rings are not seal-ing properly.

6. (1) When the distributor is ad-vanced to the highest steady readingand then retarded so the pointer is1/4 to1/2 inch below the highest steadyreading, and (2) if the pointer iswithin specifications and holdingsteady after making this adjustmentand (3) if the ignition is in time afterchecking with a timing light aftermaking this adjustment, the enginecan be considered to be in time.Allow one inch less for each 1000feet of elevation.

NORMAL REACTIONS

18 to 22 inches is usually referredto as the normal range for a warmedup engine at idle speed, but withgreater and greater degrees of valveo v e r l a p , this range is becomingmeaningless. Some car manufac-turers are now specifying 15 inchesas a noamal vacuum reading duringengine idle. The specifications forthe car under test should be checked.If with proper tune-up a particularengine could be adjusted to 21 inchesof vacuum, it would be considerablyout of time if the vacuum were ad-justed to only 19 inches; despite thefact that 19 is within the so callednormal range.

To adjust ignition timing with avacuum gauge, loosen the distributorsetscrew and advance to the highestSTEADY reading. Then retard

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TM 9-4910-677-14 & P

enough so the reading is 1/4 to 1/2 inchbelow the highest steady reading.An intake system leak will also lowerthe reading but it may be so smallthat the pointer may still be withinthe so called normal range. Morewill be said about intake systemleaks and timing later, but at themoment, we wish to emphasize (1)that the higher the vacuum gaugereading, the better; provided the ig-nition is not so far advanced that theengine pings under normal accel-eration and (2) that an engine is notnecessarily in perfect working orderjust because the vacuum reading iswithin the so called normal range onthe gauge.

Normal steadiness of the gaugepointer varies according to the num-ber of cylinders in the engine. Onfour cylinder engines, the intakestrokes do not overlap. The vacuumgauge responds to this with an evenrippling motion of the pointer. Onsix cylinder engines, there is onlya faint trace of this rippling and on8 cylinder engines, it is almost non-existent, except on engines whichhave overlapping valve timintg. Thebest way to become familiar with anormal steady reading is to connectthe gauge to engines known to be ingood operating condition and then tostudy the readings.

Responses of the gauge to move-ments of the throttle valve are muchmore exaggerated in a driving testthan in a floor test, but in eithercase, the vacuum will fall off whenthe throttle is suddenly opened andit will rise when the throttle is sud-denly closed. In a floor test, it isnormal for the pointer to oscillatebetween approximately 3 and 25inches as the throttle is suddenlyopened and closed. If the vacuumgauge does not respond in this way,it is an indication that leakage existseither in the form of poorly seatingvalves or in the form of poorly seal-ing piston rings.

REATION TO SPEED CHANGES

A low reading on the gauge mayindicate late ignition timing. A highunsteady reading may indicate ad-vanced timing:

Just as a vacuum gauge may beused to adjust ignition timing, itmay also be used, in much the samemanner, to adjust the idle screw in acarburetor by richening the mixtureto the highest steady reading. Thus,a faulty carburetor adjustment willaffect the vacuum reading.

Valve timing too, affects vacuumgauge readings. Valve timing can belate because of improper installationof timing gears but more commonthan this, tappets are set too loosecausing the valves to open late (andclose too early). This conditionwould reduce power considerably.Consequently, the speed of the pis-tons would be slowed and this wouldbe still another reason why the vac-uum gauge reading might be low.

Speed of the pistons will be slowedby anything that reduces power, suchas shorted spark plugs, leaky igni-tion wires, or any of a number ofignit ion di f f icult ies which mayground out a cylinder. To learn theeffect of a dead cylinder, connectthe vacuum gauge to an engine andshort out first one, then two sparkplugs, etc. and study the effect. Youmay be surprised by the small re-duction in speed and vacuum at idlespeed by shorting out only one cyl-inder, especially on an 8 cylinderengine. The reduction is greater ona 6 cylinder engine and quite notice-able on a 4 cylinder engine.

REACTION TO LEAKAGEIt should be understandable that

a leak in any of the passageways be-tween the carburetor and the cyl-inders will interfere with the flow ofair and fuel from the carburetor tothe cylinders. Defects of this natureaffect the speed of the pistons too;but much more directly they inter-fere with the actual creation of thevacuum. A leak in the manifoldgasket (depending on its size) can beresponsible for a reading anywherefrom slightly above zero to slightlybelow normal. Leakage into themanifold has much more effect onthe gauge reading than defects thataffect speed only. A very tiny leakwill lower the vacuum reading con-siderably.

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TM 9-4910-677-14 & P

(Leakage leans the mixture. When it isexcessive, it burns the valves and sparkplugs prematurely. Even in its mildestform, it causes an engine to ping. Itshould be noted that compensation can bemade in mild cases of leakage by re-tarding the spark. When this is done, theengine will not develop quite as muchpower or have quite as good mileage aswhen the leakage is corrected and thetiming advanced to where it should be.When adjusting the ignition timing witha vacuum gauge as explained previously,leakage is automatically compensatedfor. Or looking at it another way; if thevacuum gauge setting is later than thetiming light setting it usually indicatesthat intake system leakage exists. Thereare other reasons, however, why it issometimes necessary to retard the sparkfrom the timing light setting to prevent aping. Sometimes it is because of low

octane gasoline or because of com-pression being too high).

Intake system leakage is not onlyfound in the form of a leaky manifoldgasket. It might be in the form of awarped or loos e intake manifold,leaky carburetor flange gasket, wornthrottle shaft, one or more poorlyseating intake valves (for any rea-son including a tight tappet), one ormore worn intake valve guides, orleaks in any of the lines or fittingsto any vacuum operated units such aswindshield wipers, etc. All of thesedefects affect all cylinders equallyso all of them cause the vacuumgauge to give a low but steady read-ing. How low the reading dependson the size of the leak.

There are other types of leakagewhich DO NOT affect all cylindersalike and therefore DO NOT give asteady reading on the vacuum gauge.A poorly seating exhaust valve, forinstance, would affect the intake onlyfor one cylinder. Every time the in-take valve for that cylinder wouldopen (on the intake stroke of the pis-ton) exhaust gas would be drawn intothat cylinder. This momentary re-duction in vacuum would react on thegauge as a large pulse of 2 to 4 inchesand much larger than the pulsescaused by shorting out a cylinder.Of course, the size of the pulse de-pends on the size of the leak andwhere more than ore cylinder is con-cerned, the pulses change to anerratic wandering of the pointer in

fairly wide sweeps. Other defectswhich DO NOT affect all cylindersequally are a worn exhaust valveguide, a piston ring that does notseal, a leaky spark plug gasket, etc.

UNSTEADY POINTER

If the pointer moves in widesweeps of 3 or 4 inches, the troublecould be a blown head gasket betweentwo cylinders or ignition cross firingbecause of insulation breaking downeither in the distributor or in thespark plug cables. The troublecould also be weak valve springs.To determine whether or not thetrouble is due to cross firing, oneplug at a time may be shorted out todetermine which is firing its cyl-inder at the wrong time. The sweep-ingaction will stop when the offend-ing plug is shorted out.

Distributor governor weightmovements are sometimes verycritical at low engine speeds becausethere is no spring tension on them;and often they cause a continual butvery slight change in engine speed bymoving in and out. This action causesa continual advance and retard of thespark, in turn, causing the pointeron the gauge to be unsteady. Thepointer may react much the sameway if the spark is advanced beyond.the highest steady reading.

An unsteady action of the pointermay also be caused by unevenly orwidely spaced spark plug gaps or byspark plugs that are carbonized froma rich mixture or from oil; or justbecause they are too cold for theengine. An unsteady pointer may al-so be the result of small inconsistentintake system leaks, such as intakevalves shifting on their seats be-cause of worn guides or such as aworn throttle shaft in a carburetor.Ignition points that are not synchron-ized, insufficient tappet clearance,weak valve springs and sticky valvesalso cause the pointer of the gauge tobe unsteady.

Often the trouble may be isolatedby adjustment of the timing and thecarburetor and a check of the ignitioncircuit including inspection of the

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TM 9-4910-677-14 & P

plugs. If further isolation is nec-essary, the engine speed should beincreased to what would be about 12or 15 MPH. The higher speed re-duces the effect of a rich mixture,puts tension on the governor weightsand decreases the effect of smallIntake system leaks. At the sametime, it increases the effect of badvalve action.

(A) On this faster engine speed,if the pointer steadies, the troubleis ignition, car buretion, faulty dis-tributor weights or advancedtiming.

(B)If the sweeps get larger withfurther increas es in speed, thetrouble is definitely weak or brokerlvalve springs.

(C)When the sw eeps becon]eshorter and more rapid on the 111-creased engine speed, the troublecould be slight intake sjstcm leaks.Such leaks could b e duc iu stickyvalves or insufficient tappet clear-ance. Tappet clearances can k>echecked and sticking valves car] b~eliminated in most cases, at leasttemporarily, by the intr-oductlon ofoil through the intake system or byapplying Lt directly t o t h e guideswhere possible.

LOW READING

A low reading can often be ccr -rected too, Ly adju:, ting the lgnltiontiming. If it cannot be corrected inthis manner, concentrate on findingan intake system leak. Head gasketleaks to the outside atmosphere canbe located by running the engine andlistening for the escape of the burnedgases. If the escape is suspected tobe through the spark plug, the plugshould be examined closely forstreaks. If the head gasket is blownbetween two cylinders or if the ex-haust valves do not seal properly, acompression gauge test will revealthe cylinders at fault.

T o determine i f intake systemleaks are present, the ignition shouldbe shut off and the engine crankedwith the starter while the hand isheld tightly over the carhl]retor air

horn (after removing the alr clean-el.). A vacuurrj gauge reading duringcranking of at least 17 inches irldl-cates the Intake system to be fairlywell sea~d, but the higher the read-ing, the better if” the reading islow, it should IJC det., rrnined whetherthe leak is Lrlthe ,a~’luretor or ln theengine. To do this, the carburetorshould be rt, moved and the test madeagain, but this time with the mouthof the manifold cover edwlth the handor with some kind of a stopper. Ifa h~gher reading is obtained by thelatter test, then the leak is in thecar buret(,, P(,sslblya worn throttleshaft, a poor vacu,~lm llr]e, a leakyflange gasket or a cracked castingwoul(i b(, the sourct, of the trouble.With the engine ru~ning, Intake sys-tem leaks may be detected bysquirting oil around w he r e leakscould exist. If a leak is present, theoil disapp[,ars :r]to the leak. A leakbetween the intake and exhaust manif-olds ~rl the heat rl~cr 1s difficult toi[~catc kjy any othtf m e t h od than(,lirr~lr~atlc)[l of {)th[~l pc~ssi billties orby direct [,xamlllatlon.

If t}iv t~(,ubl< c.~rlnot IIP !ocatedwitl, the rt, asonlng of the previousparagra}>hs a]ded by your previousexpcrlence, in a kf a cylinder bal -ancf test tc is elate the troublefurther. A cyllnder balance test isalso useful In detf, rmlning the gener-al condition of an englrre.

COLD ENGINE TESTING

T o make a satisfactory engineanalysis with a vacuum gauge, theengine must be at operating temper-ature because there area great manydefects p r e s ent in a cold enginewhich correct themselves after op-erating temperature is reached. Anengine which is cold must be capableof developing a t least 7 inches ofvacuum in the intake manifold whilecranking t o guarantee a sufficientflow of f ue 1 into the cylinders tostart the engine. Sometimes, anengine cannot develop vacuum andwill not start because of lack of oilaround the piston rings or because ofa large intake system leak.

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TM 9-4910-677-14 & P

VACUUM BOOSTER PUMPDisconnect both sides of the pump

and connect the vacuum gauge on thewiper side. The reading should besteady between 7 and 12 inches. Aruptured diaphragm may cause highoil consumption, poor engine idle orfouling of spark plugs on one side ofthe engine.

CHOKED MUFFLERAccelerate the motor quickly

several times in rapid succession.With a clear muffler the indicatorneedle has a quick return to nor-mal each time while with a cloggedmuffler, the indicator needle willhave a tendency to be sluggish and,in severe cases, will not raise be-yond 8 inches and will show excess-ive vibration.

LIFT TESTWith the ignition switch in the

Off position, the throttle closedtightly, use the starting motor toturn the motor and note the indicatorreading. It should read between 8and 14 inches. Failure to do so in-dicates an open intake due to thebutterfly not closing properly, aleaky intake manifold gasket orburnt heat risers.CHOKE TEST

Open throttle, close the choke,and step on the starter. The gaugeshould read, at least, 2 inches, oras high as 6 inches depending on thetype of choke. If you cannot get thedesired reading, the choke valve isnot closing properly which usuallycauses hard starting.

FUEL PUMP TESTERPRESSURE TEST

To make a fuel pump pressuretest, remove the gas line from thepump to the carburetor at the fuelpump. Remove the 1/8" pipe fittingfrom the pump. Insert the 1/8" pipefitting supplied with the analyzer andfasten the hose from the pressuregauge to it. Make sure the fittingsare all air tight. Operate the motorat 10 to 15 miles per hour. Thereading on the gauge should be notless than 2, and not more than 3-1/2pounds; and not less than 1/2 poundon wide open throttle. If these read-ings are not obtained, pump repairsare necessary. On late model Olds-mobile - 6 cylinder - specificationscall for 4-1/2 pounds maximum. Onthe 8 cylinder, 3-1/4 pounds maximum.

VACUUM TESTTo make a fuel pump vacuum test,

remove the gas line from the pumpand, using the proper adapter sup-plied, attach the hose of the vacuumgauge. Operate the motor to 10 to15 miles per hour. The reading onthe gauge should be 8 or more inches.

If these readings are not obtained,pump repairs are necessary.

FUEL FLOW TESTTo determine if gas line or gas

tank is clogged, connect T fittingbetween fuel pump and line to gastank. Attach hose from gauge to re-maining nipple of tee. Operate themotor at 10 to 15 miles per hour. Ifgas line and tank cap are clear, thegauge reading will fluctuate between0 and 1 inch of vacuum, and steadyreading above one inch of vacuumindicating partially or wholly ob-structed gas line or tank cap.

MUFFLER BACK PRESSURE TESTTo make a muffler back pressure

test, it is necessary to drill and tapfor 1/8" pipe fitting in the exhaustmanifold, as near the muffler pipeflange as possible. Insert the 1/8"pipe fitting and attach the hose lead-ing to the pressure gauge. Start themotor. If a pressure of 3 pounds ormore s shown, the muffler must bereplaced. Motor speed to be approx-imately 50 miles per hour.

ALTITUDE COMPENSATOR FOR VACUUM GAUGEAltitude From Atmospheric Vacuum Gauge

Sea Level Pressure Reading - Normal MotorSea Level 14.7 181000 Feet 14.1 162000 Feet 13.6 143000 Feet 13.1 13.54000 Feet 12.5 135000 Feet 12.3 12.5

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PARTS LISTMODEL NO. 27-12 VACUUM TESTER

DESCRIPTION QTY. REQUIREDVACUUM GAGE 1 ea.

HOSE, 50” LONG, V4 “ I.D. 1 ea.ADAPTER SET

3/8-24 NF-27/16-24 N$21 /2-20 NF-21 /2-20 NF-2

5/16-24 NF-21 /8-271/4-183/8-18CARRYING CASE

INVERTED FLARE FEJvIALELNVERTED FLARE FEMALEINVERTED FLARE FEMALEFLARED MALE

FLARED MAI.EMALEMALEMALE

1 ea.1 ea.1 ea.1 ea.1 ea.1 ea.1 ea.1 ea.1 ea.

GAUGE MUST BE ADJUSTEDTO ZERO BEFORE USING.

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By Order of the Secretary of the Army:

E. C. MEYERGeneral, United States Army

Chief of StaffO f f i c i a l :

J.C. PENNINGTON

Major General, United States Army

The Adjutant General

U.S. GOVERNMENT PRINTING OFFICE: 1982 O - 388-960

TM 9-4910-677-14&P

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