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

Fuel System Diagnosis (Fuel Pressure Check):

Fuel System Diagnosis (Fuel Pressure Check):

Fuel System Circuit:

Circuit Description

When the ignition switch is turned to the "ON" position, the Powertrain Control Module (PCM) will turn "ON" the in-tank fuel pump. It will remain "ON" as long as the engine is cranking or running and the PCM is receiving ignition reference pulses. If there are no ignition reference pulses, the PCM will shut "OFF" the fuel pump in about 2 seconds after ignition "ON" or engine stops.

The fuel pump will deliver fuel to the Throttle Body Fuel Injection (TBI) unit and fuel injector, then to the fuel pressure regulator, where the system pressure is controlled to about 160-210 kPa (23-31 psia) with the ignition switch "ON" and to about 90-140 kPa (13-20 psia) with the engine idling at normal operating temperature. Excess fuel is then returned to the fuel tank.


Diagnostic Aids

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

^ Cranks, but will not run.

^ Cuts out, may feel like an ignition malfunction.

^ Poor fuel economy, loss of power.

^ Hard starts.

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

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


Test Description

Number(s) below refer to the step number(s) on 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.

2. Checks to see if fuel system pressure is within specifications with the ignition "ON," and the fuel pump running.

3. Checks the fuel pressure after the fuel pump stops. Approximately one minute after the fuel pump stops fuel pressure should stay steady at 90 kPa (13 psia).

4. Observe step 5 if no fuel pressure is indicated.