Air In Fuel System

A replacement of supply lines, fuel filters, injection pump, high pressure lines and injectors will let air enter the fuel system. Follow the specified procedure to bleed the air from the system.





Since the lift pump and injection pump provide a positive pressure through the fuel filter and supply line to the injection pump, loose connections or defective seals will show as a fuel leak.





The most usual place for air to enter the fuel system is between the inlet of the lift pump and the suction tube in the tank. The fuel tank has the outlet fitting at the top with a suction tube that extends down in the tank. Cracks or pin holes in the tube to the fitting can let air enter the fuel system.





Air in the system will make the engine: hard to start, run rough, misfire, produce low power, and can cause excessive smoke and a fuel knock.