TM10-3950-672-24-2
Air In the 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 provides 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. Fuel tanks that have the outlet fitting at the
top will have a suction tube that extends down in the
tank. Cracks or pin holes in the weld that joins 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.
5-70