9-7X L6-4.2L (2008)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis
Fuel System Diagnosis
Diagnostic Instructions
*
Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
*
Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
*
Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/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 returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe
from the engine. A 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. An electric turbine style fuel pump attaches to the fuel sender assembly inside the fuel tank. The fuel pump supplies
high pressure fuel through the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel
injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel sender assembly. The function of the venturi pump
is to fill the fuel sender assembly reservoir. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel
injection system. The fuel sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in
the fuel feed pipe and the fuel rail in order to prevent long cranking times.
Reference Information
Description and Operation
Fuel System Description (See: Computers and Control Systems/Description and Operation/Fuel System Description)
Electrical Information Reference
*
Circuit Testing (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing)
*
Connector Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs)
*
Testing for Intermittent Conditions and Poor Connections (See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections)
*
Wiring Repairs (See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs)
Scan Tool Reference
Control Module References (See: Testing and Inspection/Programming and Relearning/Control Module References)for scan tool information
Special Tools
*
CH-48027 Digital Pressure Gage
*
J 37287 Fuel Line Shut-off Adapter
Circuit/System Verification
Important:
*
Inspect the fuel system for damage or external leaks before proceeding.
*
Verify that adequate fuel is in the fuel tank before proceeding.
*
The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
*
Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.
1. Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool. You should hear the fuel pump turn ON and OFF.