Chart A5 - Fuel System Diagnosis
The ECM turns in-tank fuel pump on as long as ignition is "ON" and the engine is cranking or running. The ECM will allow the pump to run as long as it receives reference pulses from distributor. If there are no reference pulses, the ECM will shut off the fuel pump within 2 seconds after key is "ON". The fuel pump test terminal is located on left side of engine compartment. When engine is stopped, pump can be turned "ON" by applying battery voltage to test terminal. Improper fuel system pressure will result in one or all of the following symptoms: Cranks but will not run, Code 44, Code 45, engine cuts out (may feel like ignition problem), poor fuel economy, loss of power and hesitation.
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- If the fuse is blown, this test will confirm a short to ground on circuit 120. To prevent mis-diagnosis, be sure fuel pump is disconnected before test.
- This test determines if pump circuit is ECM controlled. The ECM will turn pump relay on, then turn it off after 2 seconds, if engine is not cranking or running.
- This step turns fuel pump on, if circuit 120 wiring is okay.
- This step checks for battery voltage at fuel pump relay.