Fuel lines and fittings – general information
Warning: Diesel fuel is flammable, so take extra precautions when you work on any part of the fuel system. See the Warning in Section Fuel transfer pump – check and replacement.
Warning: The pressure in the high-pressure fuel lines can be extremely high (as much as 23,200 psi), so use extreme caution when inspecting for high-pressure fuel leaks. Do not move your hand near a suspect leak – instead, use a piece of cardboard. High-pressure fuel leaks can cause severe injury.
Caution: Do not attempt to weld high-pressure fuel lines or repair lines that are bent, kinked or otherwise damaged. Replace them with factory replacement fuel lines.
Low-pressure fuel lines
1. The low-pressure side of the fuel system includes the following lines:
Fuel supply line from the fuel tank to the fuel transfer pump
Fuel return line back to the fuel tank Fuel drain manifold line at the rear of the cylinder head
Fuel supply line from the fuel filter to the fuel injection pump
2. Leaks in the low-pressure fuel lines can cause fuel starvation, which will result in low power. You should be able to smell a leak on the low-pressure side of the fuel system. If you find a leak at a fuel line connection, tighten the fitting and note whether the leak stops. If it doesn’t, the fitting might be stripped, and must therefore be replaced.
3. Obstructions in the low-pressure fuel lines can cause starting problems and, because they’re restricting the fuel supply to the fuel injection pump, they can prevent the engine from accelerating. The usual symptoms are low power and/or a white fog-like exhaust. Inspect the low-pressure fuel lines for bends, kinks and other damage. If you find a damaged line, replace it; don’t try to repair it.
4. The low-pressure lines use various types of quick-connect fittings at connection points. For step-by-step instructions showing how to disconnect and reconnect these fittings, refer to Fuel lines and fittings – repair and replacement in Fuel and exhaust systems – gasoline engines.
5. After tightening the fitting (s) and/or replacing any low-pressure fuel lines, prime the fuel system (Fuel system priming).
High-pressure fuel lines
6. The high-pressure side of the fuel system includes the following lines:
Fuel line from the fuel injection pump to the fuel rail
Six fuel lines from the fuel rail to the fuel injector connector tubes
7. Leaks in the high-pressure fuel lines are usually pretty obvious, and can be extremely dangerous. Not only as a fire hazard, but a stream of high-pressure fuel can cut right through your skin. Start the engine, put on a pair of safety goggles and move a piece of clean cardboard over and around the high-pressure fuel lines and their connections. If a high-pressure line connection is leaking, it will spray the cardboard. Tighten the fitting, then prime the fuel system (Fuel system priming). If a line itself is leaking, the line must be replaced – don’t attempt to repair a damaged line.
8. Unless you’re replacing the injection pump or some other component on the high-pressure side of the fuel system, we don’t recommend disassembling the high-pressure side of the fuel system.