GPEC

*CHECKING THE FUEL DELIVERY SYSTEM

For a complete wiring diagram Consult Diagrams/Electrical.

Diagnostic Test

1. CHECKING THE FUEL PUMP OPERATION
Turn the ignition on.

NOTE: Diagnose and repair any fuel pump control circuit or relay DTCs before continuing with this test.

With a scan tool, actuate the fuel pump control to ON (100%).

NOTE: It may be necessary to use a mechanics stethoscope in the next step.

Listen for fuel pump operation at the fuel tank. The fuel pump should operate smoothly, without excessive noise. If necessary, compare to a known good vehicle of similar year, make, and model.

NOTE: If the pump has excessive noise or grinding, the pump should be replaced.

CAUTION: Stop all actuation tests before continuing.

Is the fuel pump operating when actuated?

Yes

- Go to 2

No

- Go to 7

2. CHECKING THE FUEL PRESSURE
Turn the ignition off.

WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.

Install a fuel pressure gauge on the fuel rail.
Turn the ignition on.
With the scan tool, actuate the fuel pump relay control. Observe the fuel pressure gauge.

NOTE: The fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).

CAUTION: Stop all actuation tests before continuing.

Select the conclusion that best matches the result of the test:

Fuel pressure is within the stated specification

- Test complete.

Fuel pressure is below the stated specification

- Go to 3

Fuel pressure is above the stated specification

- Replace the fuel filter/pressure regulator.
- Perform the PCM Verification Test.Powertrain Verification Test

3. RESTRICTED FUEL SUPPLY LINE
Turn the ignition off.

WARNING: The fuel system is under a constant pressure, even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.

Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.
Install special 5/16 fuel line adapter tool #6539 between disconnected fuel line and the fuel pump module.
Attach a fuel pressure test gauge to the T fitting on tool #6539.
Turn the ignition on.
With the scan tool, actuate the fuel pump relay control. Observe the fuel pressure gauge.

NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).

CAUTION: Stop all actuation tests before proceeding.

Is the fuel pressure within specification?

Yes

- Repair or replace fuel supply line as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 4

4. SADDLE FUEL TANK
Is the vehicle equipped with a saddle type fuel tank?

Yes

- Go to 5

No

- Go to 6

5. FUEL TANK SIPHON HOSE OR FUEL LINE RESTRICTED OR DAMAGED
Turn the ignition off.

WARNING: The fuel system is under a constant pressure, even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.

Gain access to the fuel pump module and the fuel tank module.
Inspect the fuel line and siphon hose between the fuel pump module and the fuel tank module. Look for disconnected or damaged lines and hoses.
Inspect the fuel pressure regulator for damage or a condition that might cause a fuel flow problem. Make sure that it is seated in the module properly.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 6

6. FUEL PUMP INLET STRAINER
Turn the ignition off.

WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death.

Remove the fuel pump module and inspect the fuel inlet strainer for damage or a condition that might cause a fuel flow problem.
Were any problems found?

Yes

- Replace the Fuel Pump Inlet Strainer.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Replace the Fuel Pump Module.
- Perform the PCM Verification Test.Powertrain Verification Test

7. FUEL PUMP GROUND CIRCUIT OPEN OR HIGH RESISTANCE
Turn the ignition off.
Disconnect the Fuel Pump Module harness connector.
Using a 12 volt test light connected to 12 volts, check the Fuel Pump Motor Ground circuit at the Fuel Pump Module harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Replace the Fuel Pump Module.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Repair the Fuel Pump Ground circuit for an open circuit or high resistance.
- Perform the PCM Verification Test.Powertrain Verification Test