STS RWD V8-4.6L (2007)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis
Fuel System Diagnosis
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2
seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition
reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the
ignition remains ON.
The fuel system is a semi-returnless design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from
the engine. A semi-returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank.
Reducing the internal temperature of the fuel tank results in lower evaporative emissions.
The fuel tank stores the fuel supply. The fuel pump is an electric pump that is attached to the primary fuel tank module assembly. The fuel pump also
supplies fuel to the siphon jet pump, also attached to the primary fuel tank module. The siphon jet pump draws fuel from the secondary side of the fuel
tank to the primary side of the fuel tank. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors. A
fuel pressure regulator which is also located in the fuel tank, is attached to the primary fuel tank module. The fuel pressure regulator keeps the fuel
available to the fuel injectors at a regulated pressure. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe.
Circuit/System Verification
1. Turn OFF the ignition.
2. Relieve the fuel pressure. Refer to Fuel Pressure Relief.
3. Disconnect the chassis fuel hose from the fuel rail.
4. Install the J 37287 between the chassis fuel hose and the fuel rail.
5. Open the valve on the J 37287.
6. Turn ON the ignition, with the engine OFF.
7. Command the fuel pump relay ON with a scan tool.
8. Bleed the air from the CH-48027.
9. Command the fuel pump relay ON and then OFF with a scan tool.
10. Close the fuel feed pipe shut-off valve.
11. Monitor the CH-48027 for one minute.
‹› If the fuel pressure remains constant, replace the fuel sender assembly.
‹› If the fuel pressure does not remain constant, locate and replace the leaking fuel injectors.
Circuit/System Testing
Important:
* Inspect the fuel system for damage or external leaks before proceeding.
* Verify that adequate fuel is in the fuel tank before proceeding.
1. Turn ON the ignition, with the engine OFF.
2. Command the fuel pump relay ON with a scan tool.
‹› If the fuel pump does not operate, refer to Fuel Pump Electrical Circuit Diagnosis. See: Powertrain Management/Computers and Control
Systems/Testing and Inspection/Component Tests and General Diagnostics
3. Turn OFF the ignition.
4. Turn OFF all accessories.
5. Install a CH-48027.
6. Turn ON the ignition, with the engine OFF.
Important:
