Table A1-7B Fuel System Diagnosis (Fuel Pressure Check)

Diagnostic Chart:

Description:

Circuit Description

The Powertrain Control Module (PCM) will energize the fuel pump relay for 2 seconds when the ignition switch is turned to the ON position. When the fuel pump relay is energized the fuel pump will operate and pressurize the fuel system. When the engine is being cranked, or is running, the PCM will receive ignition system reference pulses and will continue to energize the fuel pump relay. The PCM will de-energize the fuel pump relay when ignition system reference pulses are no longer detected.

The fuel pump will deliver fuel to the fuel injector in the TBI unit at a controlled pressure of 160-210 kPa (23-31 psi) when the fuel pump is energized and the engine not running. When the engine is idling at normal operating temperatures the fuel pressure will be 90-140 kPa (13-20 psi). The fuel pressure regulator maintains the correct fuel pressure at all times by returning excess fuel to the fuel tank.

Diagnostic Aids

Improper fuel system pressure can result in any of the following conditions:

^ The engine cranks but will not start.

^ The engine cuts out or stalls (may feel like an ignition malfunction).

^ Poor fuel economy and a loss of power.

^ Hard starting.

One minute after the fuel pump stops, fuel pressure should hold at approximately 90 kPa (13 psi).

For fuel pressure gauge installation and removal procedures, Refer to Fuel Pressure / Testing and Inspection / Procedures / Fuel System Pressure Test. Testing and Inspection

If fuel pressure is normal and symptoms still exist, Refer to Symptoms. Testing and Inspection

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

3. Checks to see it fuel system pressure is within specifications with the ignition ON, and the fuel pump running.

4. Checks the fuel pressure after the fuel pump stops. Approximately one minute after the fuel pump stops fuel pressure should remain steady at 90 kPa (13 psi).

6. This step checks for a faulty check valve in the fuel pump.

7. This step checks for a faulty fuel pressure regulator.

10. This step checks for a faulty fuel pressure regulator.

14. This step checks the operation of the fuel pressure regulator.