99 dodge 3500 cummins... its getting air between the fuel cup and the outlet side of the lift pump.. I think its in the fuel cup.. Is that possible. I'm tryng not to spend the 300 $ on the cup.. Any help would would help me...

 

there are a couple places to look first the hose from the lp to the fuel filter is notoriously lame replace it and use decent clamps, the banjos on the lp must be clean and the washers must be in the right place or it will leak air and not start or just try to start but not quite. the fuel return and feed lines at the frame under the floor board are another good spot. if you have a frame mounted pusher pump unplug the stocker and hotwire the pusher, does it try to start if so you know the air leak is between the pusher and ip, it will try to start because the stock pulls air in while te pusher just pushes fuel out.