Air In Fuel Problem

[allan3306]

My truck is a 91 idi and just finished a complete body swap due to cancer beyond repair and the body wanted to come off on it's own. After replacing all fuel lines/ return lines / lift pump/ sending unit the fuel system will prime and then ends up full of air. The lift pump was removed and replaced again but still same thing. The tank is full of fuel and i even went as fare as bypassing the tank selector and went direct to the lift pump and still same thing. Any input would be great and THANKS in advance.

 

[Silver Burner]

I just had a problem and found out that the check valve next to the bleeder valve on top of the fuel filter was stuck open allowing tons of air in. It's the little brass fitting that the return line attaches to from the injector. Take it out and see if you can see light through it. If you can, replace it and I bet it'll fix the problem. It fixed mine.

 

[johneich]

I understand there are three check valves 2 on IP and 1 on filter, is there a low cost place these can be bought? These would be good to carry as spares behind the seat?

 

[allan3306]

Found fuel in oil and further inspection revealed fuel leaking from injection pump shaft seal at gear. Installed new pump and primed system. Truck ran for about 2 hours and shut down by itself. Fuel filter was full of air again and would not prime. Installed electric pump at tank and the pump is pushing but still full of air. All check valves where checked and replaced filter housing. Would anyone have more ideas besides setting it on fire because i am close to that point.

 

[gatorman21218]

Did you replace all the rubber olives on the hard fuel lines (not the injection lines)? Also did you put the clamps back on the steel injection lines? If not then they will crack, but I doubt that will cause enough air to enter the system.

Are both the fuel tanks full? if not then maybe you tank selector valve is stuck and sucking air from one tank and fuel from another

Another thing there are some o-rings in the fuel water separator that can leak too. You might try a fuel filter with a built in separator and see if that helps

 

[flareside_thun]

Are you running the one piece filter or the two piece?

One piece:
http://www.myfishingpictures.com/data/500/medium/ford_fuel_filter_002.jpg

Two piece:
http://www.intellidog.com/dieselmann/int.jpg

if it's the latter, that could be letting air in....just a thought.

 

[allan3306]

Thanks to everyone for your advice and suggestions but the problem was a crack in the tank selector on the frame side. I bypassed it and ran off the saddle tank. It has ran steady now for 14 hours with out shutting down and no power issues as well.

 

[gatorman21218]

Search on here about manual fuel selector valves. A user by the name of Midnight Rider knows alot about them. I plan to put them in if ever my factory unit fails