Hierarchy of likely
fuel injection faults
Disconnect the ECU
Ground pin 20, then pin 21 of the ECU
- Pump
doesn't run? Either or both relays is/are bad;
stop
and repair
- Pump
runs? Pump relay is OK; proceed
Remove ground from pin 20; leave pin 21
grounded, then ground pin 18
-
Fuel
injectors do not click? Fuel System relay is bad,
or corrosion in the large round connector;
stop
and repair.
- Fuel
injectors click? Proceed
-
Check
for voltage on pin 5 of the air mass meter connector
-
No
voltage? System relay is bad;
stop and repair.
-
Voltage
OK? System relay is OK:
proceed
Reconnect ECU. Connect meter (dc volts, 3
volt scale) across a fuel injector.
Crank engine. 0.3 to 1 volt
indicated, injectors are clicking, pump is running?
- If
YES TO ALL, the fuel system is working well enough that the engine should at least
start (although
the Air Mass Meter could be bad).
- If
no voltage, no injector clicks and pump does not run, then something is probably
wrong in the crank sensor circuit.
- If
only the pump runs or only the injectors show voltage and click, suspect the
ECU.
- NOTE: ECU
failures are NOT common; the problem is almost always
something simpler, such as a relay, or corrosion.
AND A FINAL NOTE: I once read voltage over and over and
over again at the injectors - the voltage was there, but corrosion in the round
connector prevented any significant current from flowing. SO be sure that
you have current as well as voltage - make sure the injectors click. They
may be hard to distinguish when the engine is running or cranking, but you
should definitely hear them in the pin 18 test.
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