Fuel Supply Line: Description and Operation

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 filter back to the fuel tank. The fuel pipes consist of 2 sections:
- The rear fuel pipes are connected to the fuel sender assembly at the top of the fuel tank and deliver fuel to the fuel filter, which is mounted to the chassis. The rear fuel pipes are constructed of nylon.
- The chassis fuel pipe is located under the vehicle and delivers fuel from the fuel filter to the fuel rail. The chassis 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. There are 3 sizes of nylon pipes used:
- 9.53 mm (3/8 inch) ID for the fuel feed
- 7.94 mm (5/16 inch) ID for the fuel return
- 12.7 mm (1/2 inch) 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.