Envoy 2WD V8-5.3L VIN P (2004)
Steps 18-25
The numbers below refer to the step numbers on the diagnostic table.
4. This step tests for an internal fuel leak.
5. This step tests the fuel pump check valve for a leak down condition.
6. This step tests the fuel pressure regulator.
10. This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.
11. This step tests for a leaking fuel injector or for a leaking fuel pressure regulator.
14. This step tests for a restricted fuel return pipe.
16. This step determines if the fuel pressure regulator or the fuel pump is the cause of the low fuel pressure.
18. This step verifies that a circuit condition is not the cause of a fuel pressure concern.
Fuel System Diagnosis - With Returnless Fuel System
FUEL SYSTEM DIAGNOSIS (WITH RETURNLESS FUEL SYSTEM)
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 filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of
