the fuel supply line from fuel tank to fuel filter housing.the fuel return line back to fuel tank.the fuel drain line from each fuel injector.the fuel supply line from fuel filter to fuel injection pump.the fuel injection pump return line.the fuel line from fuel injection pump to fuel rail.the four fuel lines from fuel rail up to the fuel injectors High-pressure fuel lines deliver diesel fuel under extreme pressure from the injection pump to the fuel injectors. This may be as high as 180,000 kpa (26,107 psi) . Use extreme caution when inspecting for high-pressure fuel leaks. Inspect for high-pressure fuel leaks with a sheet of cardboard. High fuel injection pressure can cause personal injury if contact is made with the skin.