Fuel Pump Relay: Description and Operation

Powertrain Control Module (PCM) Wiring:

PURPOSE
The PCM controls the fuel pump relay which operates the in-tank fuel pump.

OPERATION
When the key is first turned "ON" (key in "RUN" position with engine "OFF"), the PCM will turn the fuel pump relay "ON" for two seconds. This build up the fuel pressure for cranking. If the engine is not started within two seconds, the PCM will shut the fuel pump "OFF" and wait until distributor reference pulses are present. As soon as the engine is cranked, the PCM will turn the relay "ON" and "RUN" the fuel pump. The Oil pressure switch is provided as a backup to the fuel pump relay.

LOCATION
LH side of engine compartment, in micro relay center.

DIAGNOSTIC NOTES
- The PCM will monitor the fuel pump circuit for proper operation and set the appropriate PCM code if necessary.

- The PCM monitors voltage on the fuel pump power CKT 120 to detect fuel pump voltage supply faults.

- A faulty fuel pump relay can result in long cranking times, particularly if the engine is cold.

- An inoperative fuel pump would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.