Yukon/Denali 2WD V8-4.8L VIN V (2005)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis
FUEL SYSTEM DIAGNOSIS
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
two 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 two 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
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 pump and 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.
TEST
