Envoy 4WD V8-5.3L VIN P (2004)
Fuel Supply Line: Description and Operation
Fuel System (Without Returnless Fuel System)
FUEL FEED AND RETURN PIPES
The fuel feed pipe carries fuel from the fuel tank to the fuel rail assembly. The fuel return pipe carries fuel from the fuel rail assembly back to the fuel
tank. The fuel pipes consist of 2 sections:
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The rear fuel pipe assemblies are located between the top of the fuel tank and the chassis fuel pipes. The rear fuel pipes are constructed of nylon.
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The chassis fuel pipes are located under the vehicle and connect the rear fuel pipes to the fuel rail. These pipes are constructed of steel with
sections of rubber hose covered with braiding.
NYLON FUEL PIPES
CAUTION: Refer to Fuel and EVAP Pipe Caution in Service Precautions.
Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There are 3 sizes of
nylon pipes used: 9.5 mm (3/8 in) ID for the fuel supply, 7.6 mm (5/16 in) ID for the fuel return, and 12.7 mm (1/2 in) ID for the vent. Heat resistant
rubber hose or corrugated plastic conduit protects the sections of the pipes that are exposed to chafing, to high temperatures, or to vibration.
Nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if nylon fuel pipes are forced into sharp
bends, the pipes kink and restrict the fuel flow. Also, once exposed to fuel, nylon pipes may become stiffer and are more likely to kink if bent too far.
Take special care when working on a vehicle with nylon fuel pipes.
FUEL PIPE O-RINGS
O-rings seal the threaded connections in the fuel system. Fuel system O-ring seals are made of special material. Service the O-ring seals with the
correct service part.
