Chapter 14RoverMEMS - MPi/SPiContentsOverview of system operationCatalyticconverter and emission control. . . . . . . . . . . . . . . . . . . .. 6Control functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2

Fuel injection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Ignition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4Introduction' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Primary trigger. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3

AdjustmentsAdjustment pre-conditions 7Idle adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Ignition timing checks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9

Throttle adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 8

System sensor and actuator tests -

Air temperature sensor (ATS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Carbon filtersolenoid valve (CFSV). . . . . . . . . . . . . . . . . . . . . . . . . . 31

Coolant temperature sensor (CTS) 19ECMvoltage supplies and earths. . . . . . . . . . . . . . . . . . . . . . . . . . . 24Fuelinjector operation (MPi) 14Fuel injector operation (SPi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

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SpecificationsVehicle

Rover MEMS MPi114 1.4 GTi 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214 1.4 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220 2.0 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220 2.0 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .220 2.0 OOHC 16V turbo cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414 1.4 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414 1.4 OOHC 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .416 1.6 OOHC 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420 2.0 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420 2.0 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420 2.0 OOHC 16V turbo cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .620 2.0 OOHC 16V turbo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .820i 2.0 OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .820 2.0 OOHC 16V turbo cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Metro 1.4 GTi OOHC 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MGF 1.8 OOHC 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MGF 1.8 WC OOHC 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Montego 2.0 EFi ...........................................Montego 2.0 EFi AT ........................................

Rover MEMS SPiMetro 1.4 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Metro 1.4 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '. . . . . . .Metro 1.4 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Mini Cooper 1.3i MT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MiniCooper 1.3iAT ........................................MiniCooper 1.3i Cabriolet ...................................Mini1.3 ..................................................111 .....................................................114 .....................................................114 1.4i & Cabrio cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114 1.4i 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214/414 non cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214/414 cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .214 1.4 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414 1.4 16V cat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414 1.4 16V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Fuel pressure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Fuel pump and circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Inertia switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Knocksensor (KS) .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Manifoldheater (SPi engines only) 23MAPsensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Multi-function unit (MFU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Oxygen sensor (OS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Phase sensor (CID) 16Primaryignition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Primary trigger - crank angle sensor (CAS) .. . . . . . . . . . . . . . . . . . . 11Stepper motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

System relays. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Throttle potentiometer sensor (TPS) 21Throttleswitch (TS) 20Pin table - typical 36-pin and 18-pinFault codes -Obtaining fault codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

. I:Year idle speed CO%

1991 to 1994 850 ::I:50 0.75 max1992 to 1996 875 ::I:50 0.5 max1991 to 1994 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01992 to 199p 875 ::I:50 0.5 max1995 to 1996 875 ::I:50 0.5 max1995 to 1996 875 ::I:50 0.5 max1991 to 1994 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01994 to 1996 800 ::I:50 0.3 max1991 to 1996 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01991 to 1994 850 ::I:50 0.5 to 2.01995 to 1996 875 ::I:50 0.3 max1995 to 1996 875::1:50 0.3 max1989 to 1992 750 ::I:50 2.0 to 2.51989 to 1992 750 ::I:50 2.0 to 2.5

1990 to 1992 850::I:50 0.5 to 2.01990 to 1992 850 ::I:50 0.5 to 2.01993 to 1997 850 ::I:50 0.5 to 2.01991 to 1992 850 ::I:50 0.5 to 2.01991 to 1992 850::I:50 0.5 to 2.01993 to 1997 850 ::I:50 0.5 to 2.01996 to 1997 850 ::I:50 0.4 max1995 to 1997 850 ::I:50 0.4 max1995 to 1997 875 ::I:50 0.4 max1991 to 1994 875 ::I:50 0.75 max1991 to 1993 875 ::I:50 0.75 max1989 to 1992 850 ::I:50 0.5 to 2.01990 to 1992 850 ::I:50 0.5 to 2.01992 to 1996 850 ::I:50 0.5 to 2.01992 to 1996 850::I:50 0.5 to 2.01995 to 1996 850 ::I:50 0.5 to 2.0

14.2 Rover MEMS - MPi/SPi

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Overview of system operation

1 Introduction

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Please read this overview of Rover MEMSoperation in conjunction with Chapter 2,which describes some of the functions inmore detail.

The Rover MEMS (Modular EngineManagementSystem) was developed jointly byRover and Motorola, and first appeared in 1989on Montego 2.0 carburettor and then MPivehicles. MEMS is a fully-integrated systemthat controls primary ignition, fuelling and idlecontrol from within the same ECM (seeillustration 14.1). When fitted to carburettedengines, it is known as the ERICsystem.

MEMS was designed as a modular systemthat was capable of controlling a wide rangeof engines equipped with either MPi or SPi.Additionally, the ECM is designed for a harshenvironment. It is robustly built, andincorporates short-circuit protection inconsideration of its location in the enginecompartment.

Prior to 19.94, there were three mainproduction versions of MEMS. These arelabelled versions 1.2, 1.3 and 1.6. From mid-1994, version 1.8 was fitted.

The differences between the versions areas follows:

a) Version 1.2 (the first production version)was designed for non-catalyst engines.Although a catalyst could be fitted to theexhaust system of vehicles with v1.2, thecatalyst would be of the non-regulatedtype. Version 1.2 is identified by a single36-pin multi-plug connector to the ECM.

b) Version 1.3 is a fully-regulated catalystversion with ECM control of emissioncontrols. Version 1.3 is identified by twomulti-plug connectors (36-pin and 18-pin)to the ECM. .

Improvements in internal organisationreJ~as-en' 'llt'al' are-as- of Mt:MS, amr cnlbwan'1fie"

return of a single 36-pin multi-plug connectorto the ECM. However, turbocharged vehiclesretain the twin multi-plug connectors.

From mid-1994, MEMS version 1.8 hasbeen in production. Main changes are fitmentof a plastic inlet manifold and a new steppermotor. The new stepper motor no longer actsupon the linkage to the throttle plate, but usesthe motor to actuate a valve mounted withinthe inlet manifold. Very late versions fitted toKR6 and MGF vehicles utilise wasted sparkDIS and variable valve control NVc).

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14.1 RoverMEMS(Rover214SPi).Multi-point systemsare very similar

1 Throttlepedal switch 9 Throttlebody heater (inlet 16 Fuelpump relay2 Inertiaswitch manifold) 17 Throttlebody heater3 Fuelpump 10 CTS (inletmanifold)relay4 TPS 11 Distributor 18 Ignitioncoil5 Fuelpressure regulator 12 CAS 19 OS6 Fuelinjector 13 SO connector plug 20 OS relay7 Stepper motor 14ECM 21 CFSV8 ATS 15 Mainrelay 22 Charcoalcanister

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2 Controlfunctions

Rover MEMS - MPi/SPi 14-3

. !.:gnal processingThe MEMS ECM is designed with three

main areas of control. These are the ignition,fuel system and idle speed. The correctignition dwell and timing for all engineoperating conditions are calculated from dataprovided by the CAS (crankshaft position andspeed), and the MAP sensor (engine load).

Basic ignition timing is stored in a three-dimensional map, and the engine load andspeed signals determine the ignition timing.The main engine load sensor is the MAPsensor, and engine speed is determined fromthe CAS signal.

Correction factors are then applied forstarting, idle, deceleration, and part- and full-load operation. The main correction factor isengine temperature (CTS). Minor correctionsto timing and AFR are made with reference tothe air temperature sensor (ATS) and throttlepotentiometer sensor (TPS)signals.

The basic AFR is also stored in a three-dimensional map, and the engine load andspeed signals determine the basic injectionpulse value. Using the speed/density method,MEMS calculates the AFR from the pressurein the inlet manifold (MAP) and the speed ofthe engine (CAS).

This method relies on the theory that theengine will draw in a fixed volume of air perrevolution. The AFR and the pulse durationare then corrected on reference to ATS, CTS,battery voltage and rate of throttle opening(TPS). Other controlling factors aredetermined by operating conditions such ascold start and warm-up, idle condition,acceleration and deceleration. Duringacceleration, additional injection pulses areprovided at 80° crankshaft intervals.

MEMS accesses a different map for idlerunning conditions, and this map isimplemented whenever the idle switch isclosed and the engine speed is at idle. Idlespeed during all warm-up and normal hotrunning conditions is maintained by the idlespeed stepper motor. However, MEMS makessmall adjustments to the idle speed byadvancing or retarding the timing, and thisresults in an ignition timing that is foreverchanging during engine idle.

Basic ECM operationOnce the ignition is switched on, a voltage

supply to ECM pin 11 is made from theignition switch. This causes the ECM toconnect pin 4 to earth, so actuating the mainfuel injection relay. A relay switched voltagesupply is thus made to ECM pin 28, fromterminal 87 of the main fuel injection relay.Depending on model, the coil is supplied withvoltage from either the main relay or from theignition switch direct.

The majority of sensors (other than thosethat generate a voltage such the CAS, KS andCID sensor), are now provided with a 5.0-voltreference supply from a relevant pin on theECM. When the engine is cranked or run, aspeed signal from the CAS causes the ECM toearth pin 20 so that the fuel pump will run.Ignition and injection functions are alsoactivated. All actuators (Injectors, ISCV, FTVVetc) , are supplied with nbv from the mainrelay, and the ECM completes the circuit bypulsing the relevant actuator wire to earth.

Self-diagnostic functionMEMS provides a serial port for diagnostic

and system tuning purposes. The port allowstwo-way communication, so that certainparameters can be changed (ie CO value) andactuation of various output components.

In addition, a self-test capability regularlyexamines signals from the engine sensors, andinternally logs a code in the event of a faultbeing present. This code can be extractedfrom the MEMS serial port by a suitable FCR. Ifthe fault clears, the code will remain loggeduntil the FCR is used to erase it from memory.

LOS (limp-home mode)MEMS has a limited operating strategy

(LOS)or limp-home facility, and in the event ofa serious fault in one or more of the sensors,the EMS will substitute a fixed default value inplace of the defective sensor.

For example, in limp-home mode thecoolant temperature sensor (CTS)value is setto 60°C, the ATS is set to 35°C, and engineload is based on rpm. The engine mayactually run quite well with failure of one ormore minor sensors. However, since thesubstituted values are those of a hot engine,cold starting and running during the warm-upperiod are likely to be less than satisfactory.Also, failure of a major sensor, ie the MAPsensor, will lead to a considerable reduction inperformance.

Adaptive andnon-volatile memory

Over a period of time, the ECM will learn thebest idle position for a particular engine -irrespective of age, engine condition and load,so that the correct idle speed is alwaysmaintained. The adaptive idle settings arestored in non-volatile memory. Consequently,a replacement ECM will need some time to re-learn the system parameters before properidle control is restored. A tune-up with asuitable FCR is recommended whenever anew ECM is fitted.

Faults identified by the self-diagnosticfunction will also be stored in non-volatilememory, and will remain there until erased by asuitable FCR. This allows the self-diagnosticfunction to retain data of an intermittent nature.

Adaptive idle measurements and faultcodes retained in non-volatile memory cannotbe lost - even if the vehicle battery isremoved. If the ECM from one vehicle is

transferred to another vehicle, the contents ofnon-volatile memory will also be transferred,unless a FCR is used to erase the codes and

tune the engine to the new set-up.

Reference voltageVoltagesupply from the ECM to the engine

sensors is made at a 5.0-volt reference level.

This ensures a stable working voltage,unaffected by variations in system voltage.

The earth return connection for most enginesensors is made through ECM pin number 30,and this pin is not directly connected to earth.The ECM internally connects pin number 30 toearth via the ECM earth pin that is directlyconnected to earth.

Signal shieldingTo reduce interference (RFI), a number of

sensors (eg the crank angle sensor, knocksensor and oxygen sensor) use a shieldedcable. The shielded cable is connected to themain ECM earth wire at terminal 29 to reduceinterference to a minimum.

3 Primarytrigger

Crank angle sensor (CAS)The primary signal to initiate both ignition

and fuelling emanates from a CAS mountednext to the flywheel. The CAS consists of aninductive magnet that radiates a magnetic field.The flywheel incorporates a reluctor diskcontaining 34 steel pins set at 10° intervals.Asthe flywheel spins, and the pins are rotated inthe magnetic field, an AC voltage signal isgenerated to indicate speed of rotation. Thetwo missing pins (set at 180° intervals) are areference to TDC, and indicate crankshaftposition by varying the signal as the flywheelspins. One missing pin indicates TDC forcylinders 1 and 4, and the other missing pinindicates TDC for cylinders 2 and 3.

The peak-to-peak voltage of the speed signalcan vary from 5 volts at idle to over 100volts at6000 rpm. The ECM microprocessor containsan analogue-to-digital converter to transformthe AC pulse into a digital signal.

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4 Ignition14

Data on engine load (MAP) and enginespeed (CAS)are collected by the ECM, whichthen refers to a three-dimensional digitalignition map stored within its microprocessor.This map contains an advance angle for basicload and speed operating conditions. Theadvance angle is corrected after reference toengine temperature (CTS), so that the bestignition advance angle for a particularoperating condition can be determined.

14-4 Rover MEMS - MPi/SPi

AmplifierThe MEMS amplifier contains the circuitry

for switching the coil negative terminal at thecorrect moment to instigate ignition. Thesignal received by the amplifier from the CAStrigger is of an insufficient level to completethe necessary coil switching. The signal isthus amplified to a level capable of switchingthe coil negative terminal.

The amplifier circuitry is contained withinthe ECM itself, and the microprocessorcontrols the ignition dwell period for eachcondition of engine speed and batteryvoltage.

Dwell operation in MEMS is based upon theprinciple of the 'constant-energy current-limiting' system. This means that the dwellperiod remains constant at about 3.0 to3.5 ms, at virtually all engine running speeds.However, the dwell duty cycle, whenmeasured in percent or degrees, will vary asthe engine speed varies.

Ignition coilThe ignition coil utilises low primary

resistance in order to increase primary currentand primary energy. The amplifier limits theprimary current to around 8 amps, and thispermits a reserve of energy to maintain therequired spark burn time (duration). In DISsystems, the coils are double-ended, and firetwo spark plugs together. The KR6 utilisesthree DIScoils, and the MGF two DIS coils.

DistributorIn the MEMS system, the distributor only

serves to distribute the HT current from thecoil secondary terminal to each spark plug infiring order. The distributor is located on theinlet camshaft at the cylinder No 4 end. Thedistributor contains a rotor arm, and also hasa deflector plate and oil drain to prevent oilseal leakage from contaminating thedistributor cap and rotor arm.

Distributorlessignitionsystem (DIS)

Vehicles with the KR6 V6 engine, and thosewith the four-cylinder MGF WC engine utilisewasted spark DIS ignition. The MGF withoutWC is equipped with a distributor. Refer toChapter 2 for a detailed description of wastedspark and DIS.

Knock sensor(some MPi vehicles)

The optimal ignition timing (at enginespeeds greater than idle) for a given high-compression engine is quite close to the pointof onset of knock. However, running so closeto the point of knock occurrence means thatknock will certainly occur on one or morecylinders at certain times during the engineoperating cycle.

Since knock may occur at a differentmoment in each individual cylinder, MEMSemploys a knock control processor (KCP)built into the ECM to pinpoint the actual

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cylinder or cylinders that are knocking. Theknock sensor is mounted on the engine block,and consists of a piezo-ceramic measuringelement that responds to engine noiseoscillations. This signal is converted to avoltage signal that is proportional to the levelof knock, and returned to the ECM forevaluation and action.

The ECM will analyse the noise from eachindividual cylinder, and uses a sophisticatedtechnique to recognise knock as distinct togeneral engine noise.

Initially, timing will occur at its optimalignition point. Once knock is identified, themicroprocessor retards the ignition timing forthat cylinder in steps of 0.625° until eitherknock ceases or a maximum retard of 10° isreached. The timing is then advanced in0.65° increments until the reference timingvalue is achieved or knock occurs again,when the processor will retard the timing oncemore. This procedure continually occurs sothat all cylinders will consistently run at theiroptimum timing.

If a fault exists in the KCP, knock controlsensor or wiring, an appropriate code will belogged in the self-diagnostic unit, and theignition timing retarded by 10.5° by the LOSprogram.

5 Fuel injection

Rover has adopted three distinct methodsfor providing fuel to the engines equippedwith MEMS. The methods are simultaneousmulti-point injection (MPi), sequential multi-point injection (MPi) and single-point injection(SPi).

Because of the modularity of MEMS, verylittle difference exists between the implemen-tation of each system on the various engines.First, a description of common features and adescription of each type follows.

The injector(s) are switched using twocircuits. Operation depends on the principlethat more current is required to open aninjector than to keep it open. This kind ofsystem is often termed 'current-controlled'.Once the injector is open, a second circuitrapidly pulses the injector to earth. Theswitching is so rapid that the injector iseffectively held open, and less current isrequired during the operation. Advantages ofthis arrangement include a reduction ininjector operating temperature, andimmediate injector closure once the holdingcircuit is switched off.

The MEMS ECM contains a fuel map withan injector opening time for basic conditionsof speed and load. Information is thengathered from engine sensors such as theMAP sensor, CAS, CTS, ATS and TPS. As aresult of this information, the ECM will look upthe correct injector pulse duration right acrossthe engine rpm, load and temperature range.

The fuel injector is a magnetically-operatedsolenoid valve that is actuated by the ECM.Voltage to the injectors is applied from thefuel pump relay, and the earth path iscompleted by the ECM for a period of time(called pulse duration) of between 1.5 and10 milliseconds. The pulse duration is verymuch dependent upon engine temperature,load, speed and operating conditions. Whenthe magnetic solenoid closes, a back-EMFvoltage of up to 60 volts is initiated.

The amount of fuel delivered by theinjector(s) is determined by the fuel pressureand the injector opening time - otherwiseknown as the pulse duration. The ECMcontrols the period of time that the injector isheld open, and this is determined by thesignals from the various sensor inputs. Duringengine start-up from cold, the pulse durationand number of pulses (frequency) areincreased to provide a richer air/fuel mixture.

Over-speed fuel cut-off(rev limiter). To prevent over-high engine speeds, which

might otherwise lead to engine damage,above 6250 rpm (MPi) and 6860 rpm (SPi),MEMS inhibits the injector earth path. As theengine speed drops below 6150 rpm and6820 rpm respectively, fuel injection isreinstated.

Deceleration fuel cut-offA deceleration fuel cut-off is implemented

during engine over-run conditions, to improveeconomy and reduce emissions. Theconditions for over-run to be implementedare:

a) Throttle closed (throttle pedal contactsclosed).

b) Engine speed above 2600 rpm (MPij or1500 rpm (SPij.

c) Coolant temperature above BO°C.d) Once the engine speed drops below

2600 rpm or 1500 rpm respectively, fuelinjection is reinstated.

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Multi-point injection(MPi -simultaneous)

The MPi system consists of one injector foreach cylinder, mounted in the inlet port, sothat a finely-atomised fuel spray is directedonto the back of each valve. The injectors areall pulsed simultaneously, twice per enginecycle. Half of the required fuel per enginecycle is injected at each engine revolution.

Fuel will briefly rest upon the back of avalve before being drawn into a cylinder.Unlike other simultaneous systems, theinjectors are all connected to the ECM viaseparate wires to separate ECM driver pins.

Multi-point injection(MPi -sequential)

The sequential system functions in a similarmanner to the simultaneous system.However, with reference to the signal from thecylinder identification (CID) sensor (only

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Rover MEMS -MPi/SPi 14-5

present in sequential systems), each injectoris actuated as its inlet valve opens, in firingorder.

s Single-point fuel injection (SPi)The SPi system consists of a single injector

mounted in the throttle body. The amount offuel delivered by the injector is determined bythe fuel pressure and the injector openingtime -otherwise known as the pulse duration.

In SPi engines, fuel is injected into the inletmanifold, where it mixes with air. Thedepression produced by a descending pistoncauses the resulting air/fuel mixture to bedrawn into each cylinder. Otherwise, operationOtt{1einjector is very similar to operation of the

inje~d to the MPi systems.

Cylinder identification sensor(sequential injection only). In simultaneous MPi systems, the ECMdoes not have to recognise No 1 cylinder, orind~ed even the firing order. When thecrankshaft or distributor provides a timingsignal, the correct cylinder is identified by themechanical position of the crankshaft,camshaft, valves and ignition rotor.

On models fitted with sequential injection,the ECM must determine which cylinder is onits firing stroke, and the CID sensor providesthe appropriate signal. The CID sensoroperates on the inductive principle, and is apermanent magnet device mounted adjacentto the camshaft. A reluctor is attached to thecamshaft, divided into four equal quadrants.Each quadrant contains a unique number ofteeth, numbering from one to four. Becausethe AC-generated signal from each quadrantis unique, the ECM is able to determine thecamshaft position and cylinder sequence.

The reluctor should be handled withextreme care, due to the fragile sinteredmaterial used in its construction. Any impactmay cause cracking or a stress fracture.

MAP sensor

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The main engine load sensor is the MAPsensor. A vacuum hose connects the MAPsensor (located within the ECM) and the inletmanifold (see illustration 14.2). Manifoldvacuum acts upon the MAP sensordiaphragm, and the ECM converts thepressure into an electrical signal. MAP iscalculated from the formula: AtmosphericPressure less Manifold Pressure = ManifoldAbsolute Pressure.

Using the speed/density method, MEMScalculates the AFR from the MAP signal andthe speed of the engine (CAS). This methodrelies on the theory that the engine will draw ina fixed volume of air per revolution.

The. inlet manifold on the MPi models is a'dry' manifold. Since fuel does not enter themanifold - due to injection being made ontothe back of the inlet valve, there is no risk offuel being drawn into the MAP sensor tocontaminate the diaphragm, and a fuel trap isnot used. However, on Rover 820 models

Clads are

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14.2 SPi: The MAP sensor vacuumhoseconnections to the fuel trap at the air filter.

The hoses are colour coded to ensurecorrect refitting

under certain operating conditions, fumes aredrawn from the rocker box into the MAPsensor vacuum hose and then to the ECM,where contamination can occur. This can beprevented by fitting the fuel trap used on SPimodels.

The inlet manifold on the SPi models is a'wet' manifold. Fuel is injected into the inletmanifold, and there is a risk of fuel beingdrawn into the MAP sensor to contaminatethe diaphragm. This is prevented by runningthe vacuum hose upward to the air filter,through a fuel trap and then to the ECM(which contains the MAP sensor).

Air temperature sensor (ATS)The ATS is mounted in the air inlet casing

(MPi) or air filter casing (SPi), and measuresthe air temperature before it enters the inletmanifold. Because the density of air varies ininverse proportion to the temperature, theATS signal allows more accurate assessmentof the volume of air entering the engine.

The open-circuit supply to the sensor is at aS.O-volt reference level, and the earth path isthrough the sensor return. The ATS operateson the NTC principle. A variable voltage signalis returned to the ECM based upon the airtemperature. This signal is approximately2.0 to 3.0 volts at an ambient temperature of20°C, and reduces to about 1.S volt as thetemperature rises to around 40°C.

Although the air filter casing used on SPimodels contains a thermal valve system, thethermal valve has no bearing on the AFR, andthe air temperature is calculated solely byreference to the ATS.

CO adjustmentThe CO value at idle speeds can only be

adjusted through the medium of a FCRattached to the serial port. It is not possible tomake this adjustment by any other means. Oncatalyst-equipped models, the CO is non-adjustable.

Coolant temperature sensor(CTS)

The CTS is incorporated in the coolingsystem, and contains a variable resistancethat operates on the NTC principle. When the

engine is cold, the resistance is quite high.Once the engine is started and begins towarm-up, the coolant becomes hotter, andthis causes a change in the CTS resistance.As the CTS becomes hotter, the resistance ofthe CTS reduces (NTC principle), and thisreturns a variable voltage signal to the ECMbased upon the coolant temperature.

The open-circuit supply to the sensor is at aS.O-volt reference level, and this voltagereduces to a value that depends upon theCTS resistance. Normal operating tem-perature is usually from 80° to 100° C. TheECM uses the CTS signal as a main correctionfactor when calculating ignition timing andinjection duration.

Throttle potentiometer sensor(TPS)

A TPS is provided to inform the ECM of rateof acceleration. The TPS is a potentiometerwith three wires. A S.O-volt reference voltageis supplied to a resistance track, with theother end connected to earth. The third wire isconnected to an arm which wipes along theresistance track, and so varies the resistanceand voltage of the signal returned to the ECM.

From the voltage returned, the ECM is ableto calculate just how quickly the throttle isopened. From model year 1993 onwards, theTPS also informs the ECM of idle position witha voltage of approximately 0.6 volts.

Throttle pedal switchUntil the 1993 model year, the throttle pedal

switch indicated a closed throttle to the ECM.The ECM was then able to recognise the idlespeed condition and also deceleration. From1993 models year, MEMS recognised theclosed throttle condition with reference to theTPS signal.

Stepper motorThe stepper motor is an actuator that the

ECM uses to automatically control idle speedduring normal idle and during engine warm-up(see illustration 14.3). When electrical loads,such as headlights or heater fan etc areswitched on, the idle speed would tend todrop. In this event, the ECM advances theignition timing to make a small speed change,and indexes the stepper motor for a greaterchange in idle speed. During periods of cold

14.3 Rover 820 stepper motor1 Stepper motor 2 Ignition coil 3 ECM

14-6 Rover MEMS - MPi/SPi

"

running, the stepper motor will open thethrottle so that the engine rpm willbe set to asuitable fast idle speed. Also, on sensing lowbattery voltage, the ECMwillincrease the idlespeed to allowgreater alternator output.

The stepper motor is a DC motor, providedwith a voltage supply from the system relay.The motor windings are earthed through fourearth wires. Byearthing various combinationsof the four wires, the ECMis able to indexthemotor to its correct position. The ECMcontrols idle speed by using the steppermotor in one of two diverse ways.Throttle plate actuator

The stepper motor controls a cam andpush rod through a reduction gear. Thepush rod contacts the throttle lever, whichactuates the throttle plate and so maintainsthe correct idle speed. Maximum movementof the stepper motor is 3.75 revolutions, andthis is accomplished by 180 steps of 7.5°. Thereduction gear reduces the actual cammovement to 150°.Inlet manifold air valve

The air valve stepper motor is an actuatorthat the ECM uses to automatically controlidle speed during normal idle and duringengine warm-up. When the throttle is closed,the throttle valve is locked in a position wherevery little air passes by. The throttle positionthen, willhave no effect upon the idle speed.

A by-pass port to the throttle plate islocated in the inlet manifold. A valve ispositioned inthe port. As the valve moves, thevolume of air passing through the port willvary, and this directly affects the idle speed.The idle speed then, depends upon theposition of the stepper air valve in the by-passport. This method of idle control is fitted tosome models (principally those with theplastic inlet manifold)fromthe middleof 1994.

Adaptive idle controlSince the idle control is adaptive, over a

period of time, the ECM will learn the bestposition for a particular engine - irrespectiveof age, engine condition and load, so that thecorrect idle speed is always maintained.Consequently, a replacement ECM willneedsometimeto re-learnthe systemparametersbeforeproper idlecontrol is restored.

Adaptive idle measurements are retained innon-volatile memory and cannot be lost -even if the vehicle battery is removed. Onmodels prior to 1993, idle position wasdeterminedby an idle switch locatedon theacceleratorpedal.From1993, this switch hasbeen discontinued,and the idle positien isnow determined by the TPS.

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11.,

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Manifold heater (SPi)The ECM controls the manifold heater

through a relay. This heater works on the PTCprinciple, and allows a greater current toquickly heatthe inlet manifold during the warm-up period. This allows better driveability duringengine warm-up. Once a preset temperature of

U...!....

14.4 Rover 820 MEMS multi-function unit(MFU)

MFU multi-plug disconnected

approximately 75° C is reached, the ECM tumsoff the relay. If the ignition is switched to the'on' position and the engine is not cranked, theECM will turn off the manifold heater after a fewseconds. The manifold heater will also be

turned off to prevent battery overload duringengine cranking.

MEMS relays and MFUThe MEMS electrical system is controlled by

a number of relays. The relays utilised in somevehicles are conventional in construction andoperation. However, some models areequipped with an MFU (multi-function unit).Main and fuel pump relays(Rover 214, 414, 220 and 420 models)

A permanent voltage supply is made tomain relay terminals 30 and 86, and fuel pumprelay terminal 30, from the battery positiveterminal. When the ignition is switched on, theECM earths terminal 85 through ECM terminalnumber 4, which energises the relay winding.This causes the main relay contacts to close,and terminal 30 is connected to the outputcircuit at terminal 87. A voltage supply is thusoutput at terminal 87. Terminal 87 suppliesvoltage to the injector(s), ECMterminal 28, theignition coil terminal 15 (some models) andthe stepper motor. In addition, voltage issupplied to the manifold heater relay terminal86 on SPi vehicles.

When the ignition is switched on, a voltagesupply is made to fuel pump relay terminal 86,and the ECM briefly earths relay contact 85 atECM terminal 20, which energises the fuelpump relay winding. This causes the fuelpump relay contacts to close, and connectsvoltage from terminal 30 to terminal 87.Voltage is thereby output to the fuel pumpcircuit. After approximately one second, theECM opens the circuit and the pump stops.This brief running of the fuel pump allowspressure .to build within the fuel pressurelines, and provides for an easier start.

The fuel pump circuit will then remain openuntil the engine is cranked or run. Once theECM receives a speed signal from the CAS,the fuel pump winding will again be energisedby the ECM, and the fuel pump will run untilthe engine is stopped.

Multi-function unit (MFU)main andfuel pump relays (all Rover modelsother than 214, 414, 220, and 420)

The MFU is a sealed box that contains foursets of relay contacts. The two relays alwaysused are a main and fuel pump relay, and theother two will be chosen from the starter, OS ormanifold heaterrelays (see illustration 14.4).

If anyone of the relays fails, the whole MFUmust be replaced. However, the relaycontacts are heavy-duty, and failure is a fairlyrare occurrence.

Two multi-plugs of 8-pin and 6-pinconfiguration connect the MFU with MEMSwiring. The multi-plug terminal designationsare identified by the prefix 8 or 6 for the multi-plug, and the suffix 1 to 8 or 1 to 6 for theactual terminal. So 8/1 would identify theterminal as number one terminal in the eight8-pin multi-plug. There follows a typicaldescription, but be warned that wiring ofsome MFU's may differ.

A permanent voltage supply is made to theMFU main relayterminals 8/6 and 8/7 from thebattery positive terminal. When the ignition isswitched on, the ECM earths terminal 6/3through ECM terminal number 4, whichenergises the relay winding. This causes themain relay contacts to close, and outputvoltage is available at MFU terminal 8/1, 8/3and 8/8. These output terminals supply voltageto the injector(s),ECM terminal 28, the ignitioncoil terminal 15 models) and the stepper motor.Connections to individual components varyaccording to vehicle. In addition, voltage isintemally supplied to the manifold heater relayinside the MFU on SPi vehicles.

When the ignition is switched on, a voltagesupply is made to MFU terminal 6/2, and theECM briefly earths MFU contact 6/1 at ECMterminal 20. This energises the fuel pumprelay, and causes the fuel pump relaycontacts to close. Terminal 8/6 is thusconnected to terminal 8/4, and voltage isthereby output to the fuel pump circuit. Afterapproximately one second, the ECM opensthe circuit, and the pump stops. This briefrunning of the fuel pump allows pressure tobuild within the fuel pressure lines, andprovides for an easier start.

The fuel pump circuit will then remain openuntil the engine is cranked or run. Once theECM receives a speed signal from the CAS,the fuel pump winding will again be energisedby the ECM, and the fuel pump will run untilthe engine is stopped.

Engine shut downOn switching off the engine, the ECM keeps

the relay (or MFU) earth energised for up to 30seconds. This holds the voltage supply to theECM, which-thef-l actuates the stepper motorto its fully closed' osition (thus preventingengine run-on). After a seconds more, theECM actuates the stepper motor to a positionwhere it slightly opens the throttle plate, readyfor the next engine start.

Rover MEMS - MPi/SPi 14-7

14.5 Fuel delivery circuitfor SPi engines

1 Fuel tank2 Fuelpump3 Swirlpot4 Non-returnvalve5 Fuel filter6 Fuelinjector7 Fuelpressure

regulator8 Fuelreturnline9 Venturi

Fuel pressure systemNote: Uniquely, the Montego utilises a roller-type fuel pump mounted outside the fuel tank.Voltage to the fuel pump is applied through a1.0 ohm ballast resistor. This reduces the

voltage and current applied to the fuel pump,and ensures cooler running. Duringcranking,when a higher voltage level is required, voltageis applied directly to the pump from the startersolenoid and the resistor is by-passed. Full nbvis thus applied to the fuel pump.

The fuel system includes a fuel tank, withswirl pot and a submerged fuel pump. Thefuel pump draws fuel from the tank andpumps it to the fuel rail via a fuel filter (seeillustration 14.5). -

Switching the ignition key on causes theECM to energise the fuel pump relay forapproximately one second so that the fuelsystem is pressurised. The fuel pump relay isthen switched off, to await a cranking orrunning signal. The swirl pot prevents air fromentering the fuel supply line, by ensuring thatthe pick-up strainer is always immersed in fuelwhen the fuel level is low - even during fuelmovement due to centrifugal forces actingupon the vehicle.

The pump is of the 'wet' variety, in that fuelactually flows through the pump and theelectric motor. There is no actual fire risk,because the fuel drawn through the pump isnot in a combustible condition. The fuel pumpassembly comprises an outer and inner gearassembly, termed a 'gerotor'. Once the pumpmotor becomes energised, the gerotorrotates, and as the fuel passes through theindividual teeth of the gerotor, a pressuredifferential is created. Fuel is drawn throughthe pump inlet, to be pressurised between therotating gerotor teeth, and discharged fromthe pump outlet into the fuel supply line.

To reduce the effect of fluctuations in fuelpressure, a pulsation damper is provided inthe pump outlet, thereby preventing hydraulicknock. The pump is protected from over-pressurising by a' relief valve mounted in theinlet side of the pump. Once the engine isrunning, fuel is fed through a non-return valveand fuel filter to the multi-point injector rail orthe single throttle body injector.

To prevent pressure loss in the supplysystem, a non-return valve is provided in the

fuel pump outlet. When the ignition isswitched off, and the fuel pump ceasesoperation, pressure is thus maintained forsome time. Temperature in the fuel rail ismonitored by a fuel rail temperature sensor(FRTS)in manual transmission models; a fuelrestrictor and fuel temperature sensor (FTS)isused in automatic transmission models.

Fuel pressure regulator (MPi)Fuel pressure in the fuel rail is maintained at

a constant 2.5 bar by a fuel pressure regulatorfitted on the outlet side of the fuel rail. The fuelpump normally provides much more fuel thanis required, and surplus fuel is thus returnedto the fuel tank via a return pipe. In fact, amaximum fuel pressure in excess of 5 bar ispossible in this system.

The pressure regulator consists of twochambers, separated by a diaphragm. Theupper chamber contains a spring, whichexerts pressure upon the lower chamber andcloses off the outlet diaphragm. Pressurisedfuel flows into the lower chamber, and thisexerts pressure upon the diaphragm. Oncethe pressure exceeds 2.5 bar, the outletdiaphragm is opened, and excess fuel flowsback to the fuel tank via a return line.

A vacuum hose connects the upperchamber to the inlet manifold, so thatvariations in inlet manifold pressure will notaffect the amount of fuel injected. This meansthat the pressure in the rail is always at aconstant pressure above the pressure in theinlet manifold. The quantity of injected fuelthus depends solely on injector opening time,as determined by the ECM, and not on avariable fuel pressure.

At idle speed with the vacuum pipedisconnected, or with the engine stopped andthe pump running, or at full-throttle, thesystem fuel pressure will be around 2.5 bar. Atidle speed (vacuum pipe connected), the fuelpressure will be approximately 0.5 bar underthe system pressure.

Fuel pressure regulator (SPi)Fuel pressure of approximately one bar is

controlled by the pressure regulator, which islocated within the throttle body next to the -injector. As the pressure rises over the pre-determined level, excess fuel is returned tothe fuel tank via a return pipe.

Fuel rail temperature sensor(FRTS) -some MPi models withmanual transmission

The FRTS senses the temperature of thefuel in the fuel rail, and the value is logged bythe ECM at the time that the engine is shutdown. When the engine is restarted, the ECMcompares the start-time temperature with thetemperature recorded at shut-down. If thenew temperature is higher, the injection pulseis lengthened during the cranking operation toprovide hot start enrichment. This enrichmentdecays at a fixed rate.

Fuel temperature sensor (FTS)and fuel restrictor solenoid(FRS) -MPi models withautomatic transmission)

In vehicles with automatic transmission, theFRTS is replaced with a fixed resistance sothat after-start enrichment will never beimplemented. When the fuel rail temperatureexceeds 90°C, the FTS closes to completethe earth circuit to the FRS. The FRS isenergised to cause a restriction in the fuelreturn line. The increased fuel pressurethereby improves starting.

Inertia switchThe inertia switch is a safety cut-out switch,

used to isolate the fuel pump in the event of avery sharp deceleration - eg a collision.Oncethe switch has been activated, the electricalsupply to the fuel pump remains open-circuituntil the inertia switch has been reset byraising the button (see illustration 14.6).

Temperature gauge(Montego only)

The engine coolant temperature gauge onthe instrument panel is connected to earththrough the ECM. MEMS actuates the gaugeand warning lamp by rapidly pulsing the ECMconnection to earth. This produces a squarewaveform of variable frequency and dutycycle. The frequency increases as the enginetemperature increases, and the hotter theengine, the lower will the average voltagebecome. In addition, the duty cycle will alsochange.

14.6 Reset inertia switchby depressing plunger

14.8 Rover MEMS - MPi/SPi

TurbochargerReferto Chapter 2 fora detailed description

of turbocharger operation. An intercooler,which is a kind of air radiator, for cooling isused in Rover turbo models. Boost control iscontrolled by the ECM so that maximum useis made of the turbo during appropriateoperating conditions.

Air by-pass (turbo models)Turbo lag is reduced on Rover turbo

models by use of an air by-pass valve. Asensing pipe connects the by-pass valve withthe inlet manifold. When the turbine suppliescompressed air to the manifold, thecompressed air pushes upon the air by-passvalve, and it remains shut. Duringdecelerationor light load when the turbo is inactive, themanifold contains depressed air (a vacuum)and the depression willopen the air by-passvalve. Airpressure from the impellerwheel iscirculated throughout the turbochargerhousing, and prevents a back pressureforming. The turbine slows very little, andturbo lag is much reduced when theaccelerator is re-applied.

6 Catalyticconverter andemission control

'

1

1I.I

From January 1993, all new cars in the UKare fitted with a catalyst as standardequipment.

Adjustments

~14.7 Carbon filter solenoid valve (CFSV)

1 Wiringconnector2 Inlethose, charcoalcanister to GFSV3 Outlet hose, GFSV to throttlebody4 G-cIip5 Inlethose, connector6 0 ring7 GFSV

The MEMS injection system fitted tocatalyst vehicles implements a closed-loopcontrol system, so that exhaust emissionsmay be reduced. Closed-loop systems arefitted with an oxygen sensor (OS) whichmonitors the exhaust gas for its oxygencontent. A low oxygen level in the exhaust

signifiesa rich mixture.A high oxygen level inthe exhaust signifiesa weak mixture.

The OS only produces a signal when theexhaust gas, has reached a minimumtemperature of approximately300°C. In orderthat the OS will reach optimum operatingtemperature as quickly as possible after theengine has started, the OS contains a heatingelement.

The OS heater supply is made from the OSrelay terminal number 87. This ensures thatthe heater willonly operate whilst the engineis running. Under full-load conditions, theheater supply is cut-off by the ECM byinhibitingthe earth path of the OS relay. TheKR6engine utilises twin oxygen sensors, onefor each bank.

Carbon filter solenoid valve(CFSV)

A CFSVand activated carbon canister willalso be employed to aid evaporative emissioncontrol (see illustration 14.7). The carboncanister stores fuel vapours until the CFSVisactuated by MEMS.CFSV actuation occurswhen the engine temperature is above 70°C,the engine speed above 1500 rpm and theMAPsensor returns less than 30 kPa.

When the CFSV is actuated by MEMS,thevalveis modulated on and off,and fuelvapoursare drawn into the inletmanifoldto be bumt bythe engine during normalcombustion. So thatengine performance will not be affected, theCFSV remains closed during cold engineoperation and also duringengine idle.

~

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7 Adjustmentpre-conditions

1 Ensure that all of these conditions are metbefore attempting to make adjustments:

I

a) Engine at operating temperature. Engineoilat a minimumtemperatureof aOOG.A journey of at least 4 miles is advised(particularly so if equipped with A1).

b) Ancillary equipment (allengine loads andaccessories) switched off.

c) AT engines: Transmission in N or P.d) Engine mechanically sound.e) Engine breather hoses and breather

system in satisfactory condition.f) Induction system free from vacuum leaks.g) Ignition system in satisfactory condition.h) Air filter in satisfactory condition.ij Exhaust system free from leaks.j) Throttle cable correctly adjusted.k) No fault codes logged by the EGM.I) OS operating satisfactorily (catalyst

vehicles with closed-loop control).

.1I

l

2 In addition, before checking the idle speedand CO value stabilise the engine as follows.a) Stabilise the engine. Raise the engine

speed to 3000 rpm fora minimum of30 seconds, and then let the engine idle.

b) If the cooling fan operates duringadjustment, wait untilit stops, re-stabilisethe engine, and then restart theadjustment procedure.

c) Allowthe GOand idlespeed to settle.d) Make allchecks and adjustments within

30 seconds. If this time is exceeded, re-stabilise the engine and recheck.

8 Throttleadjustments

1 Clean the throttle valve and surroundingareas with carburettor cleaner. Blow-by fromthe breather system often causes stickingproblems here (see illustration 14.8).2 The throttle valve position is critical, andmust not be disturbed.3 The TPS in not adjustable for this range ofengines.

JSC~-'I

14.8 Adjust the throttle lost motion gap -see text

1 The clearanceshould beequal on both sides

2 Adjustment nut3 Locknut

Rover MEMS - MPi/SPi 14.9

--- t-- - - - -----

9 700 timingchecks.p... ----

1 The ignition timing is not adjustable onthese models, and timing marks are notprovided.

, - -- --10 Idle adjustments

I

Adjustments (idle tune)1 Idle speed and CO level (non-cat modelsonly) are only adjustable through the use of asuitable FCR connected to the serial port.2 Before connecting the FCR, check thethrottle lost motion gap.3 After completing the idle tune, recheck thethrottle lost motion gap.

System sensor and actuator tests

Adjustment of the throttle lostmotion gap (typical)4 Switch the ignition on.5 From within the engine compartment, usethe throttle lever to fully open the throttlevalve. The ECM will index the stepper motorto 25 steps.6 Allow the throttle valve to fully close.7 Adjust the throttle cable so that an equalgap exists either side of the lost motionlever.8 Switch off the ignition key. The steppermotor will revert to normal control.

Important notesPlease refer to Chapter 4, which describes common test procedures applicable to this system. The routines in Chapter 4 should be read in

conjunction with the component notes and wiring diagrams presented in this Chapter. The wiring diagrams and other data presented in thisChapter are necessarily representative of the system depicted. Because of the variations in wiring and other data that often occurs, even betweensimilar vehicles in any particular VM's range, the reader should take great care in identification of ECM pins, and satisfy himself that he hasgathered the correct data before failing a particular component.MEMSECMterminals

The multi-plug terminals at the MEMS ECM are gold-plated, and care must be taken that the plating is not removed during procedures thatinvolve probing or back-probing. The terminal wires are sealed with a rubber plug, and you should not back-probe through these plugs, or piercethem with a sharp object. If the rubber plug is damaged, it will lose its water-sealant qualities. The following method is strongly recommended toprevent damage to terminal or sealing plug.

First, disconnect the multi-plug and detach the white cover. Carefully insert a small jeweller's-type screwdriver into the recess at the top of theterminal pin. Gently lever out the plastic retainer leg, and gently pull on the wire from behind the multi-plug. Once the clip is disengaged, theterminal should slide easily from its holder. Slide the rubber plug up the wire, and then push the terminal back into the multi-plug. Repeat thisprocedure for all terminal pins that will be back-probed during a test. After testing is completed, the procedure should be reversed, and all sealantplugs refitted into their original position.

Moulded component multi-plugsFrom about 1994, many Rover models are fitted with moulded multi-plugs to the components. This means that it is no longer possible to

backprobe the component. Live voltage or oscilloscope tests must therefore be made at the ECM or with the aid of a break-out box (BOB).Component BOB's suitable for this purpose are available from the suppliers of engine test equipment.

1 Refer to the notes at the start of this 1 Refer to the notes at the start of Section 11, 1 Refer to the notes at the start of Section 11,Section, and refer to the relevant Section of and refer to the relevant Section of Chapter 4. and refer to the relevant Section of Chapter 4.Chapter 4. 2 A knock sensor is only used in 2.0 litre2 The CAS resistance is 1100 to 1700 ohms engines with MPi.

11 Primarytrigger -crank angle sensor (CAS)

12 Primary ignition

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4(see illustration 14.9).2 The primary ignition is essentially that of anECM with internal amplifier.3 Primary resistance (distributor ignition) is0.71 to 0.81 ohms. Secondary resistance is5000 to 15 000 ohms.

4 Primary resistance (DIS ignition) is 0.63 to0.77 ohms.

13 Knock sensor (KS)

14 Fuel injector operation (MPi)

- - .J

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.2 Voltage to the injectors is provided fromeither the system relay or MFU.3 MEMS fuel injector operation is current-controlled.4 Injector operation is either simultaneous orsequential.5 The injector resistance is normally 15.0 to17.0 ohms.

- - -.....15 Fuel injector operation (SPi)

III- - - lE

ECM11 Isupplyfrom281 ignition switch

tacho -oninstrumentpanel

CAS1' 2

fl>whOOIOignitioncoil

EQH1414earth

14.9 Typical local wiring diagram: ignition

14.10 Rover MEMS - MPi/SPi

EOH1417

8 9 33 30 16

e'arth

KS TPS CTS ATS

14.10 Typical local wiring diagram:sensors

2 Voltage to the injectors is provided fromeither.the system relay or MFU.3 The SPi system is current-controlled.4 The injector resistance is normally 1.1 to1.5 ohms.

16 Phase sensor (CID)

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.2 The CID phase sensor is located adjacentto the camshaft.

3 Unfortunately, no data is available for CIDresistance, but failure is likely to be indicatedbya short- or open-circuit reading.

17 MAP sensor

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4(see illustration 14.10).2 The MAP sensor is incorporated. into theECM, and separate voltage tests are notpossible.3 Performance of the MAP sensor can bequickly evaluated by a suitable FCR attachedto the serial port. Select Datastream; thevalues should be similar to those detailed inthe MAP table (see Chapter 4, Section 18).

18 Airtemp,eraturesensor (ATS)

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.2 The ATS is mounted in the air inlet casing(MPi) or in the air filter casing (SPi).

--~-"""'~ ~ .-

19 CGolant temperatUre sensor(CTS)

--'-"""""''''

1 Refer to the notes at the start of Section 11,

and refer to the relevant Section of Chapter 4.

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20 Throttle switch (TS)

1 On pre-1993 models equipped with thethrottle pedal.-mounted 'idle switch', theengine will gasp, die and fail to respondproperly if the engine speed is increased bymoving the throttle lever directly from underthe bonnet. This is because the ECM links theidle switch closed condition with rpm, andenters fuel deceleration cut-off mode. The

engine rpm should only be increased by useof the accelerator pedal from inside the car.2 However, during testing it is sometimesmore convenient to be able to control theengine speed by moving the throttle leverdirectly. It is possible' to by-pass the idleswitch by disconnecting one 'of the wires onthe pedal switch. MEMS will assume a fault,and set a default value. The engine will thenrespond to throttle lever movement. .3 Once testing is complete, the pedal switchwire must be reconnected, and a FCR used toclear the ECMof any logged faults.4 Check that the terminal pins are pushedhome and making good contact with thepedal switch.

Checking pedal switch operation5 The two wires to the pedal switch multi-plug connector are earth and idle signal.6 With the engine stopped, and ignition on,connect the voltmeter negative probe to anengine earth.7 Connect the voltmeter positive probe to thewire attached to the pedal switch signalterminal number 2.,The meter should indicatezero volts.8 If zero volts cannot be obtained:

a) Check the pedal switch earth connection.b) Make the pedal switch resistance tests

(below).

9 Crack open the throttle. The voltage shouldrise to 5.0 volts.10 If the voltage is low or non-existent:a) Check that the pedal switch idle terminal

is not shorted to earth. .

b) Disconnect the pedal switch connections,and check for5.0 volts at the signalterminal.If there is no voltage, check forcontinuityof the signal wiringbetween thepedal switch and the ECM.

11 If the pedal switch wiring is satisfactory,check all voltage supplies and earthconnections to the ECM. If the voltagesupplies and earth connections aresatisfactory, the ECM is suspect.

Pedal switch resistance tests12 Connect an ohmmeter between the earthterminal 1 and terminal 2.13 With the pedal switch closed, theohmmeter should indicate very close to zeroohms.14 Slowly open the throttle, and as the pedalswitch cracks open, the resistance should

14.11 Check the throttle pot voltageoutput with the aid of a voltmeter

become open-circuit and remain so - even asthe throttle is opened fully.15 If the pedal switch does not behave asdescribed, and if it is not prevented fromopening or closing fully by a binding throttlelinkage, the ECM p.edalswitch is suspect.

21 Throttle potentiometersensor (TPS)

1 Refer to the notes at the start of SectiOn 11,and refer to the relevant Section of Chapter 4(see illustration 14.11).

22 Stepper motor

1 Switch the ignition key to the 'on' position.2 After 5 seconds, switch the ignition key tothe 'off' position. The stepper motor plungershould fully retract, and then step to thecorrect position (according to temperature),ready for the next engine start. After15 seconds, the main relay will audibly 'clickout' . If this operation is completedsatisfactorily, it is probable that the steppermotor condition is also satisfactory.

Stepper motor tests3 Check for nbv to the stepper motor supply.4 Connect a DC voltmeter to each of theearth pins in turn (see illustrations 14.12and 14.13).5 Switch the ignition key on and off. A voltageshould be briefly seen as the stepper motoractuates.

6 Disconnect the stepper motor multi-plug,and check the resistance from pin 5 to pins 1,2, 3 and 4 in turn; 16 ohms should' beobtained between pin 5 and e?ichearth pin.

Rover MEMS - MPi/SPi 14-11

.ECM2 3 22 27 24 23 . 26

supptyfrommainrelay: t87

23164" Stepper

motor

EOH1418

inj 1 inj2 inj3 inj4

14.12 Typical local wiring diagram:injectors, stepper motor

14.13 Stepper motor multi-plugpin numbers

7 Disconnect the ECM multi-plug (refer toWarning No 3 in Reference)8 Switch the ignition key 'on'.9 Connect a jumper lead from ECM pin 4 tobattery earth (this energises the main relaywith the ECM disconnected).10 Connect a voltmeter between earth andECM pins 22, 2. 27 and 3 in turn. nbv shouldbe obtained.11 If nbv is not obtained at one or more ofthe ECM pins. check the continuity of thewiring between the relevant ECM and steppermotor pins.12 If the stepper motor wiring is satisfactory.check all voltage supplies and earthconnection~ to the ECM. If -the' voltagesupplies and earth connections aresatisfactory, the ECM is suspect."

-- - - - -- -- - -23 i!Manifold heater

(SPi engines only)

-- . --- ----..--1 Referto the notes at the start of Section 11.and refer to the relevant Section of Chapter 4.2 Make tests when the engine coolanttemperature is less than 75°C. Note: If theengine is hot. a variable potentiometer couldbe connected to the CTS multi-plug so that acold engine could be simulated.3 If a FCR is available. the manifold heaterrelaycan be "actuated via the serial port. Thisliould prove the integrity of the relay andassociated wiring.

14.14 Probing for nbv at theECM multi-plug

- -.. - - - - - -.--24 ECMvoltage supplies

and earths

1 Refer to the notes at the start of Section 11.and refer to the relevant Section of Chapter 4(see illustration 14.14). .

2 In addition to relay drivers for the main relayand pump relay. relay drivers may be availablefor the manifold heater and OS relays.

25 Inertia switch

1 Refer to the notes at the start of Section 11.and refer to the relevant Section of Chapter 4.2 Montego models only: check the ballastresistor by-pass.3 The inertia switch may be located behindthe radio (early models) or in the enginecompartment. close to the bulkhead.

ECM

29 36 18 72142028

EARTH f--.

screoen ~ ---,..---~ ::-H

, 26 System relays

.

.

.I1 Power to the MEMS electrical circuits isprovided by either a number of conventionalrelays or an MFU (multi-function unit).2 When a conventional set of relays are used.testing also follows conventional lines. In thisinstance. please refer to Chapter 4, whichdescribes common test proceduresapplicable to checking standard systemrelays found in Rover MEMS systems. Theroutines in Chapter 4 should be read inconjunction with these component notes andthe wiring diagrams portrayed in this Chapter(see illustration 14.15).3 In the Rover MEMS system. the OS andmanifold heater are also supplied from a relay.

- _l1li'- 011-

27 Multi-function unit (MFU) ,

JQuick relay test1 Aquick method of determining whether therelay is defective would be:a) By-pass the MFU and attempt to run the

engine.b) Check for voltages at the MFU output

terminals or at the components suppliedby the relay.

2 If the wiring and MFU operation aresatisfactory, yet the ECM fails to operate oneor more of the relays, the ECM is suspect.

86 30.

STEPPERMOTOR

IN.£CTORS

IGNITION COIL

I,

1 2

CFSV

OXYGEN SENSOR

14.15 Typical local wiring diagram: relays and components

14-12 Rover MEMS - MPi/SPi

STEPPER MOTOR

FUEL PUMP OXYGEN CFSV

14.16 Typical local wiring diagram: relays (MFU)and components

- - -- - - -- --Testing the MFU3 Ignitionkey on, relayconnected.4 Backprobe or probe for voltages atcomponents supplied by the relay. Ifthere isno output, backprobe at the appropriate MFUoutput terminal. Ifthere is still no output, andall supply and earth voltages are satisfactory,the MFUis suspect (see illustrations 14.16to 14.18).5 Ifone of the MFUrelays is judged faulty,theMFUmust be renewed complete.

MULTIFUNCTIONUNIT

812

EARTH

STARTER SOLENOID

- - ---I 28 Fuelpump and circuit

---- - - - -

~14.17 Multi-function unit (MFU)

1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.

--- --29 Fuel pressure

- --- ----1 Refer to the notes at the start of Section 11,

and refer to the relevant Section of Chapter 4.

14.18 MFU multi-plug

30 Oxygen sensor (OS)

- -- - - --- - --- - - - -1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.2 The OS found in the majority of RoverMEMS systems is a four-wire sensor with aheater.

31 Carbon filtersolenoid valve(CFSV)

-- --- --1 Refer to the notes at the start of Section 11,and refer to the relevant Section of Chapter 4.

Pin table - typical 36-pin/18-pinNote: Refer to illustration 14.19.

Terminal 'A'1 Injector cylinder 42 Stepper motor phase 23 Stepper motor phase 14 Main relay driver5 -6 -7 Oxygen sensor signal8 TPS signal9 TPS supply10 Diagnostics output11 Ignition switch supply12 -13 -14 Earth15 Diagnostics input

16 ATS17 KS18 Oxygen sensor return19 AC magnetic clutch relay20 Fuel pump relay driver21 CFSV

22 Stepper phase 323 Injector pulse cyl 224 Injector pulse cyl125 Ignition coil26 Injector pulse cyl 327 Stepper motor phase 428 Supply from main relay29 ECM earth30 Sensor return31 CAS +

32 CAS return33 CTS34 FRTS35 AC high press safety sw36 Oxygen sensor relay driver

Terminal'S'3 Alternator5 OS relay driver6 Turbo boost valve8 Turbo air pressure solenoid13 OS return14 OS signal15 Camshaft sensor18 Camshaft sensor

Rover MEMS - MPi/SPi 14-13

Fault codes

t_~:n~~UR:_. . ,1 Rover MEMS requires a dedicated FCR toaccess fault codes and Datastream, actuatecomponents and make service adjustments.Flash codes are not avai"lablefor output fromthis sy,Stem.

2 MEMS does not provide too many codes,since a programmed test procedure (whenusing a Rover dedicated tester) will check thesensor and actuator circuits and report on allfaults found.

Code1210161719

FaultCTS circuit faultATS circuit fault

Fuel pump circuit faultTPS circuit fault

TPS supply voltage faultOxygen sensor heater circuit fault(cat models only)

1 12

24 +=E:IDODDDDDDDDI!I13

DDDDDDDDIJD 13 70000000000 1

25 36EClH1413

14.19 Typical 36-pin and 18-pin multi-plugs