9-7X V8-5.3L (2005)
Fuel Return Line: Description and Operation
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:
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9.5 mm (3/8 in) ID for the fuel supply
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7.6 mm (5/16 in) ID for the fuel return
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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.
ON-BOARD REFUELING VAPOR RECOVERY SYSTEM (ORVR)
The On-Board Refueling Vapor Recovery System (ORVR) is an on-board vehicle system designed to recover fuel vapors during the vehicle refueling
operation. The flow of liquid fuel down the fuel filler pipe provides a liquid seal which prevents vapor from leaving the fuel filler pipe. An evaporative
emission (EVAP) pipe transports the fuel vapor to the EVAP canister for use by the engine.
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.
