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Home >> Chevrolet >> 1998 >> Camaro V8-5.7L VIN G >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Component Tests and General Diagnostics >> Circuit Diagnosis - Fuel Pump Relay
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Circuit Diagnosis - Fuel Pump Relay

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Circuit Description

When the ignition switch is ON, the PCM activates the in-tank fuel pump. The fuel pump remains ON as long as the PCM receives reference pulses from the ignition system. If there are no reference pulses, the PCM turns the fuel pump OFF after about 2-3 seconds. The pump delivers fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure remains at 380-420 kPa (55-61 psi). Excess fuel returns to the fuel tanks. When the engine is stopped, a scan tool in the output controls function can turn ON the fuel pump.

Improper fuel system pressure results in one or many of the following symptoms:
- Cranks but will not run
- Cuts out, may feel like an ignition system concern
- Poor fuel economy
- Loss of power
- Hesitation
- DTCs

Diagnostic Aids

Important:
- Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

- For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

- The following conditions may have caused the fuel pump fuse to open:
- The fuse was faulty
- There is an intermittent short in the fuel pump power feed circuit.
- The fuel pump has an intermittent internal condition.

- For an intermittent condition, refer to Symptoms.

Test Description

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

3. Refer to the thumbnail wiring schematic for the proper terminal identification.

5. The test lamp only illuminates for two seconds even though the scan tool commanded position is ON. You will have to command the fuel pump OFF then ON to re-enable the PCM fuel pump control.

12. Inspect the fuel pump fuse for an open. If the fuse is open, test the circuit for a short to ground.

20. Inspect the fuel pump fuse for an open. If the fuse is open, test the circuit for a short to ground.

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