Air in fuel line

[Ca Rancher]

I bought diesel fuel was contaminated and white smoke started blowing out like crazy. I drained it and from the filter to the engine there is no air, but from the tank to the fuel filter there must still be air in the line. I fill up the fuel filter and everything runs good, but the fuel is not replaced from the tank. You can see by the attached photo, there is an off, on and air selection on my fuel filter. Question is what do I do when turning it to air? I also see there is a nipple or something above fuel filter - and I and wondering if I need to do something with this. Any help would be appreciated.

 

[Roadworthy]

Do you get fuel from the tank to the filter assembly? Try removing the filter and putting a can under it. See what the valve does. If you get no fuel in the "on" position check for a blockage where the fuel exits the tank. Sometimes there is a clog inside the tank itself. If you get flow to the filter check the tractor manual for the proper air bleeding sequence