Fuel Delivery and Air Induction: Testing and Inspection

FUEL SYSTEM DIAGNOSIS

DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

CIRCUIT/SYSTEM DESCRIPTION
When the ignition is turned ON, the engine control module (ECM) supplies power to the in-tank fuel pump, by energizing the fuel pump relay. The in-tank fuel pump remains ON as long as the engine is cranking or running and the ECM receives crankshaft reference pulses. If there are no reference pulses, the ECM turns the in-tank fuel pump OFF, 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running. The electric fuel pump is incorporated into the modular fuel pump and sender assembly design and is located inside the fuel tank. The fuel pump supplies fuel through a fuel filter, also located in the modular fuel pump and sender assembly, through the fuel feed pipes, to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, located in the modular fuel pump and sender assembly, keeps the fuel available to the fuel injectors at a regulated pressure. When the fuel pressure rises above the pressure regulator calibration, the pressure is relieved, with excess fuel exhausted into the modular fuel pump and sender assembly reservoir.

CIRCUIT/SYSTEM VERIFICATION
1. Ignition ON, command the fuel pump relay ON with a scan tool. You should hear the fuel pump turn ON and OFF.

IMPORTANT:
- Inspect the fuel system for damage or external leaks before proceeding.
- Verify that adequate fuel is in the fuel tank before proceeding.
- If the fuel pump does not operate, refer to Fuel Pump Electrical Circuit Diagnosis. Component Tests and General Diagnostics

2. Ignition OFF, all accessories OFF, install the J 34730-1A.
3. Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 380-427 kPa (55-62 psi).
4. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

CIRCUIT/SYSTEM TESTING
1. Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 380-427 kPa (55-62 psi).

IMPORTANT:
- The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
- DO NOT start the engine.
- If the fuel pressure is more then the specified range, replace the fuel pump.

2. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi). in 1 minute.

IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

- If the fuel pressure decreases more than the specified value, perform the following procedure:
2. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief Procedure.
3. Install the J 37287 between the fuel feed pipe and the fuel rail.
4. Open the valve on the J 37287.
5. Bleed the air from the fuel pressure gage.
6. Close the valve on the J 37287.
7. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi). in 1 minute.
- If the fuel pressure remains constant, replace the fuel pump.
- If the fuel pressure drops, locate and replace the leaking fuel injector.
3. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi). in 5 minutes.
- If the fuel pressure decreases more than the specified value, replace the fuel pump.
4. Remove the J 37287 and J 34730-1A.
5. Operate the vehicle within the conditions of the customers concern while monitoring fuel related parameters with a scan tool.
- If the scan tool parameters indicate a lean condition, test for a restricted fuel feed pipe, restricted fuel filter, or poor connections at the harness connectors and ground circuits of the fuel pump. If all test normal, replace the fuel pump.
- If the scan tool parameters do not indicate a lean condition, refer to Symptoms - Computers and Control Systems. - Symptoms - Engine Controls

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Fuel Sender Assembly Replacement
Fuel Rail Assembly Replacement