Fuel Pump: Testing and Inspection

Fuel Pump Electrical Circuit Diagnosis

Circuit Description

The engine control module (ECM) provides a ground to the coil side of the fuel pump relay. When the ignition switch is first turned On, the ECM energizes the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM de-energizes the fuel pump relay after 3 seconds.

Diagnostic Aids

Listen for a click when the fuel pump relay operates. When the fuel pump relay is commanded On with the scan tool, the ECM pulses the fuel pump relay ON and OFF several times.

For an intermittent condition, refer to Intermittent Conditions Intermittent Conditions.





Test Description

The numbers below refer to the step numbers on the diagnostic table:

2.

Listen for a click when the fuel pump relay operates. When the fuel pump relay is commanded On with the scan tool, the ECM pulses the fuel pump relay ON and OFF several times. Repeat the command as necessary.

3.

This step determines if the condition is located on the coil side or the switch side of the circuit.

7.

This step tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.

8.

This step verifies there is battery voltage to the fuel pump relay.

9.

This step jumps the fuel pump relay in order to activate the fuel pump.

13.

This step determines if the condition with the circuit is intermittent.