Checking System Function
Checking system function:
This test should only be performed after all previous test sections above have been completed, any faults found corrected and all components checked are OK. This then verifies that any faults found here depend on proper Engine Control Module (ECM) function.
Replace the Engine Control Module if a fault is found.
System function is checked by measuring voltage at injectors under different operating conditions.
Specific meter values are not important.
What is important, however, are the changes in meter deflection during different operating conditions.
Connect voltmeter to one of the fuel injectors:
- Peel back rubber cover from around injector wires.
- Connect voltmeter:
red lead (+) to yellow-red injector wire.
black lead (-) to green-white injector wire.
- Set voltmeter to measure 0 - 4 volts.
Check start function:
- Remove connectors from all injectors (so that engine does not start).
- Remove connector from coolant temperature sensor (to simulate cold start).
- Crank engine and check meter deflection.
- Deflection should be large when first cranking and then decrease.
- Reconnect coolant temperature sensor.
- Crank engine.
- Voltmeter should deflect as before but with decreased deflection.
- Reconnect injectors.
Check enrichment during warm-up:
- Start engine.
- Warm-up engine and read meter.
- As engine warms up voltmeter deflection should decrease slightly.
Connect tachometer:
- Switch off engine.
- Connect tachometer.
- Start engine.
Check idle speed:
- Idle speed should be 12.5 r/s (750 rpm).
- Engage air conditioning.
- Engine speed should increase to 15.0 r/s (900 rpm).
- Disengage air conditioning.
If engine speed does not increase with A/C engaged:
Check that air control valve does not stick.
Replace sticking valve and re-test with a new air control valve.
If engine does not idle:
Check air mass meter, (see; "Check air mass meter", section below).
Check fast idle:
- Remove connector from coolant temperature sensor (simulates cold engine).
- Engine speed should increase to 26.7 - 41.7 r/s (1600 - 2500 rpm).
- Reconnect coolant temperature sensor.
- Engine speed should return to normal idle.
Check air mass meter:
- Slowly increase engine speed.
- Meter deflection should increase with engine speed.
If incorrect, check voltage from air mass meter:
- Switch off engine.
- Peel back rubber cover from air mass meter connector.
- Connect voltmeter between terminal 7 (+) and terminal 6 (-).
- Start engine.
- Voltage should increase as engine speed increases.
- Replace and test with new engine control module (ECM) if air mass meter is OK.
Check acceleration enrichment:
- Voltmeter connected to one of the injectors.
- Quickly increase engine speed.
- Meter deflection should at first be large (= enrichment) and then reduce slightly.
Check fuel shut-off during engine braking:
- Increase engine speed to over 33.3 r/s (2000 rpm).
- Quickly release throttle control.
- Meter deflection should go down to O until engine speed reduces to approx. 23.2 r/s (1400 rpm), meter should then show deflection again.
Check full throttle enrichment:
- Remove connector from throttle valve switch (engine speed increases slightly).
- Increase engine speed to at least 58.3 r/s (3500 rpm) during check.
- Connect a jumper wire between connector terminal 18 and terminal 3.
- Meter deflection should increase slightly (= enrichment).
- Reconnect throttle valve switch.
Switch off engine:
- Remove voltmeter from injector.
- Reposition rubber connector cover.
Check air mass meter measuring wire dirt burn-off:
- Peel back rubber cover from around air mass meter wiring connector.
- Connect a voltmeter between terminal 8 (+) and terminal 36 (-).
- Start engine.
- Increase engine speed to over 33.3 r/s (2000 rpm).
- Switch off engine.
- After approx. 5 seconds voltmeter should show approx. 1 Volt for 1 second.
- Remove voltmeter.
- Reposition rubber cover around air mass meter connector.
- Reinstall panels under dashboard.
Check and adjust idle speed, CO-content: