How one test Air in Fuel?

A replacement of fuel supply lines, fuel filters, fuel injection pump, high pressure fuel lines and injectors will let air enter the fuel system. Air in the fuel system will make the engine hard to start, run rough, misfire, and produce low power and cause excessive smoke and fuel knock.

Replacing procedure of Air filter, Fuel filter of Generator:

Replacing the fuel supply lines, fuel filters, fuel injection pump, high presser fuel lines and injectors will let air enter into the fuel system. One must follow the system to bleed the air from the system.

Since the fuel transfer pump provides positive pressure through the fuel filter and supply line to the fuel injection pump, loose connections or defective seals show as a fuel leak and not as an air leak.

For faster air purge small amounts of air can be bled from the fuel injection pump by operating the hand primer located on the fuel transfer pump or by cranking the engine.

One sees a source that is often overlooked for air to enter the fuel system is between the inlet prefilter and the suction tube in the tank. Fuel tanks that have the outlet fitting at the top have a suction tube that extends to the bottom of the tank. Cracks or pin holes in the weld that join the tube to the fitting can let air enter the fuel system.

A stuck open injector can also blow combustion gas back into the pump and cause air to be present in the overflow. If the engine seems to be misfiring or running rough, break all the injector supply lines loose at the pump end.

One must use two adjustable wrench or spanner when loosening the lines at the fuel pump, one to hold the delivery valve and one to loosen the fuel line and at last tight the fuel lines where must torque value is 24 N.m = 212 in-lb.

One must follow this caution

Keep away hands and body parts from the high pressure fuel lines. Fuel comes from the high pressure fuel lines are under extreme pressure and also cause serious by penetrating the skin.

Do not vent the fuel system on a hot engine this can cause fuel to spill onto a hot exhaust manifold which can cause a fire.

This Step one must check air in the high pressure lines by loosening the fittings at the head. Crank the engine to allow entrapped air to bleed from the line. Tighten the fittings where torque value must be 38 N.m = 28 lb-ft.

Now operate the engine and vent one line at a time until the engine run smoothly.

If one show air continues to bubble out of the system for several minutes then an air leak is present.

An often overlocked source from which air can enter the fuel system is between the inlet of the fuel transfer 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 to the bottom of the tank. Cracks or pin holes in the weld that join the tube to the fitting can let air enter the fuel system.

One must be check to make sure all the fittings from the fuel supply line on the tank to the inlet of the fuel transfer pump are tight.

For checking the air in fuel supply line use a sight glass at the fuel lift pump inlet.