Fuel Pump Circuit Tests

Check Fuel Pump Operation

Connect test mode connector and turn ignition on. Ensure fuel pump operates for 2 seconds after turning ignition on. If fuel pump operates for 2 seconds, check fuel injector circuit. See FUEL INJECTOR CIRCUIT TESTS . If fuel pump does not operate, go to next step.

Check Fuel Pump Power Supply

Turn ignition switch on. Check voltage between ground and fuel pump 6-pin connector terminal No. 1. Voltage should be at least 10 volts. If voltage is 10 volts or more, replace fuel pump. If voltage is less than 10 volts, go to next step.

4) Check Harness Between Fuel Pump & Fuel Pump Relay Connector

Turn ignition off. Measure resistance between harness 6-pin connector terminal No. 1 and fuel pump relay 4-pin connector terminal No. 4. Resistance should be less than one ohm. If resistance is more than one ohm, repair open in harness between fuel pump and fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. If resistance is less than one ohm, check fuel pump 6-pin connector terminal No. 1 and chassis ground. Resistance should be more than one megohm. If resistance is less than one megohm, repair short in harness between fuel pump and fuel pump relay connector. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.

Check Fuel Pump Relay

Disconnect fuel pump relay and main relay connectors. Remove fuel pump relay and main relay from bracket. Connect battery voltage and ground to fuel pump relay terminals No. 1 and 3. Ensure there is less than 10 ohms resistance between terminals No. 2 and 4. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, replace fuel pump relay. See Fig 2. See appropriate wiring diagram in WIRING DIAGRAMS article in this section. If fuel pump relay does not click, replace relay. If fuel pump relay clicks, verify zero ohms resistance between terminals No. 2 and 4. If resistance is as specified, go to next step. If resistance is not as specified, replace fuel pump relay.

Check Harness Between ECM & Fuel Pump Relay Connector

Disconnect connectors from ECM. Measure resistance of harness between ECM connector terminal No. 32 and fuel pump relay 4-pin connector terminal No. 3. Resistance should be less than one ohm. If resistance is less than one ohm, check for poor contact in ECM connector. If resistance is more than one ohm, repair open circuit in harness between ECM and fuel pump relay. See appropriate wiring diagram in WIRING DIAGRAMS article in this section.

Fig 2: Testing Fuel Pump Relay

Courtesy of SUBARU OF AMERICA, INC.