Fuel Pump Electrical Circuit Diagnosis Non-European Emissions

When you turn ON the ignition switch, the engine control module (ECM) energizes the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no ignition reference pulses, the ECM shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

The following conditions may cause the fuel pump fuse to open:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation:

Fuel System Description

Electrical Information Reference

Scan Tool Reference

Special Tools Required

J 43244 Relay Puller Pliers

Ignition ON, command the fuel pump relay ON and OFF with a scan tool. You should hear the fuel pump turn ON and OFF when you command the fuel pump relay ON and OFF.

1. Ignition OFF, the fuel pump should not be operating.

⇒	If the fuel pump operates continuously, test for a short to voltage in the fuel pump supply voltage circuit. If the circuit/connections test normal, replace the fuel pump relay.

2. Remove the fuel pump relay from the electrical center with the J 43244 relay puller pliers.
3. Connect a test lamp between the control circuit of the fuel pump relay terminal 85 and B+.
4. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. The test lamp should respond to the scan tool commands.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests OK, replace the control module.

⇒	If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests OK, replace the control module.

5. Load test for battery voltage between the ignition 1 voltage circuit terminal 86 of the fuel pump relay and ground.

⇒	If less than B+, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal refer to Ignition Relay Diagnosis for further diagnosis.

6. Load test for battery voltage between the battery voltage circuit terminal 30 of the fuel pump relay and ground.

⇒	If less than B+, repair the battery voltage circuit for a short to ground or an open/high resistance.

7. Connect a 15-amp fused jumper wire between the battery voltage circuit terminal 30 and the supply voltage circuit terminal 87 of the fuel pump relay. The fuel pump should operate.

⇒	If the fuel pump does not operate, test for the following conditions:

•	An open/high resistance in the motor circuit of the fuel pump

•	An open/high resistance in the ground circuit of the fuel pump

⇒	If the above circuit/connections test normal, replace the fuel pump.

8. If all circuit/connections test normal, test or replace the fuel pump relay.

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the fuel pump relay.

⇒	If the resistance is not within the specified range, replace the fuel pump relay.

2. Measure for infinite resistance between the following terminals of the fuel pump relay:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If continuity is detected, replace the fuel pump relay.

3. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒	If the resistance measures more than 2 ohms, replace the fuel pump relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.