Checking The Fuel Delivery System

CHECKING THE FUEL DELIVERY SYSTEM

Special Tools:






For a complete wiring diagram, refer to the Wiring Information.

1. FUEL PUMP OPERATION
1. Ignition on, engine not running.
2. With the scan tool, actuate the Fuel System test.

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

3. Listen for fuel pump operation at the fuel tank.

Does the Fuel Pump operate?

Yes

- Go To 2

No

- Go To 5 CAUTION: Stop All Actuations.

2. FUEL PRESSURE





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 possible serious or fatal injury.

Perform the following procedure to purge air from the system:

- Open the Fuel System Isolation Valve (1).
- Close the Flow Test Valve (2).
- Ignition on, engine not running.
- With the scan tool, actuate the fuel pump.
- Open the Flow Test Valve (1) for 10 seconds, then close the Valve. CAUTION: Stop All Actuations.

- Turn the ignition off.
- Disconnect, empty and then reconnect the Reservoir Assembly.

1. Turn the ignition on, wait five seconds, turn the ignition off and then wait one minute before proceeding.
2. Read the Fuel Pressure Gauge (3) and record the reading.

Choose a conclusion that best matches your fuel pressure reading.

Below Specification

- Go To 3

Within Specification

- Test Complete.

Above Specification

- Replace the fuel pressure regulator.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. RESTRICTED FUEL SUPPLY LINE

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.

1. Turn the ignition off.
2. Disconnect the Fuel Pressure Decay Tester (8978A).
3. Raise the vehicle on a hoist and disconnect the fuel pressure line at the fuel pump module.
4. Install the Fuel Pressure Decay Tester (8978A) between the fuel supply line and the fuel pump module.
5. Ignition on, engine not running.
6. Using the scan tool, actuate the Fuel System test and observe the fuel pressure gauge.

CAUTION: Stop All Actuations.

Is the fuel pressure within specification now?

Yes

- Repair/replace fuel supply line as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. CHECKING FUEL INLET STRAINER

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 possible serious or fatal injury.

1. Turn the ignition off.
2. Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer. Fuel Pump Module - Removal.

Is the Fuel Inlet Strainer plugged?

Yes

- Replace the Fuel Pump Inlet Strainer. Fuel Pump Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Fuel Pump Module. Fuel Pump Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. FUEL PUMP OUTPUT CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the Fuel Pump Module harness connector.
3. Ignition on, engine not running.
4. With the scan tool, actuate the Fuel System test.
5. Using a 12-volt test light connected to ground, probe the Fuel Pump Output circuit.

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

Does the test light illuminate brightly?

Yes

- Replace the Fuel Pump Module. Fuel Pump Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Repair the excessive resistance or open in the Fuel Pump Relay Output circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.