Fuel Return Line: Description and Operation

FUEL FEED PIPES

The fuel feed pipe carries fuel from the fuel tank to the fuel injection system. The fuel pipe consists of 3 sections:
- The rear fuel pipe is located from the top of the fuel tank to the chassis fuel pipe. The rear fuel pipe is constructed of nylon.
- The chassis fuel pipe is located under the vehicle and connects the rear fuel pipe to the engine compartment fuel pipe. The chassis fuel pipe is constructed of steel with a section of rubber hose.
- The engine compartment fuel pipe connects the chassis fuel feed pipe to the fuel rail. The engine compartment fuel pipe is constructed of steel.

NYLON FUEL PIPES

Nylon pipes are constructed to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. The following 2 sizes of nylon pipes are used:
- 9.53 mm (3/8 in) ID for the fuel feed
- 12.7 mm (1/2 in) ID for the vent

Heat resistant rubber hose or corrugated plastic conduit protect the sections of the pipes that are exposed to chafing, high temperature, or 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. The fuel system O-ring seals are made of special material. Service the O-ring seals with the correct service part.