Rubber Fuel Hoses
The fuel feed and return pipes and hoses extend from the fuel sender to the fuel manager/filter. They are secured with clamps and are routed along the frame side member.
Nylon Fuel Pipes
Caution: In order to Reduce the Risk of Fire and Personal Injury:
• If nylon fuel pipes are nicked, scratched or damaged during installation,
Do Not attempt to repair the sections of the nylon fuel pipes. Replace them. • When installing new fuel pipes, Do Not hammer directly on the
fuel harness body clips as it may damage the nylon pipes resulting in a possible
fuel leak. • Always cover nylon vapor pipes with a wet towel before using a
torch near them. Also, never expose the vehicle to temperatures higher than
115°C (239°F) for more than one hour, or more than 90°C (194°F)
for any extended period. • Before connecting fuel pipe fittings, always apply a few drops
of clean engine oil to the male pipe ends. This will ensure proper reconnection
and prevent a possible fuel leak. (During normal operation, the O-rings located
in the female connector will swell and may prevent proper reconnection if
not lubricated.)
The nylon fuel pipes are designed in order to perform the same job as the steel or rubber fuel tubes that they replace. The nylon pipes are constructed in order to withstand maximum fuel system pressure, exposure to fuel additives and changes in temperature. There are two sizes used: 3/8 inches ID for the fuel feed, and 5/16 inches ID for the fuel return.
The fuel feed and return pipes are assembled as a harness. Retaining clips hold the pipes together and provide a means for attaching the pipes to the vehicle. The Quick-Connect type fittings are used at the fuel tank ends of the fuel feed/return pipes. Sections of the pipes that are exposed to chafing, high temperature or vibration are protected with a heat resistant rubber hose and/or corrugated plastic conduit.
The nylon fuel pipes are somewhat flexible and can be formed around gradual turns under the vehicle. However, if forced into sharp bends, the nylon pipes will kink and restrict the fuel flow. Once exposed to fuel, the nylon pipes may become stiffer and are more likely to kink if bent too far. Special care should be taken when working on a vehicle with nylon fuel pipes.
Quick-Connect Fittings
The Quick-Connect type fittings provide a simplified means of installing and connecting the fuel system components. The quick-connect fittings consist of a female socket and a compatible male connector. The O-rings, located inside the female socket, provide the fuel seal. The integral locking tabs or the fingers hold the fittings together. The metal collar quick-connect fittings have locking tabs that require a special tool in order to release. Refer to Servicing Quick Connect Fittings .
Injection Lines
The high-pressure discharge fittings on the head of the injection pump connect to the injection nozzles with steel lines of equal length and interior volume.
When the engine is running, the fuel is contained in the injection lines. During engine operation, a residual pressure of approximately 500 psi is maintained in each injection line. As the injection occurs in each line, a small amount of fuel enters the line, pushing a similar amount into the nozzle at the other end with a pressure wave.
Fuel Return System
The fuel return system has several different sizes and types of hoses and pipes. These hoses and pipes are connected to the injection pump and to each of the injection nozzles.
At the rear of the engine, the return system pipe under the intake manifold connects to a series of hoses and pipes that send the fuel back to the fuel tank.
