Air in the fuel system

[ouidosson]

I have a 1994 gmc 3500 dually 6.5 L Turbo diesel and I have air in the fuel lines! Needless to say, it stumbles and runs like crap. Is the fuel system supposed to be under a vaccum? My water in fuel lite came on but when I bleed the fuel filter I can't find any water, but do have air in the lines. Also, where is the water in fuel sensor located? Any and all help will be appreciated. I am a new diesel owner and as you see, I don't know much about them!

[rustyk]

The water sensor is in the fuel filter housing. The source of air would be between the fuel tank and the lift pump. The round "dial" on top of the filter is the air bleed. There should be a small petcock/valve mounted near the filter to drain water.

[Warren96]

Check the fuel line between the tank and the fuel pump. Even though there will be a small vaccumm on it under normal conditions, you may find a tell-tale wet spot on the line or even on the top of the fuel tank. Good Luck!

[phantom309]

How did you diagnose air in the fuel as your problem?