Well I have a bit of a problem, not sure how or where this air is getting in there. I have an 1983 300-SD converted with the dual tank system from greasecar. On both fuels, I am getting air bubbles you can see in the inlet pre-filter for the lift pump, although it's worse on WVO. the bleeder pump is the original screw type if that matters. All the lines are tight, and when I by-pass the solenoids, I still get the air being pulled into the pump. Once enough air has entered the pump it starts to idle very poorly, has no power and will eventually stall. Only way to get it going after this to go out and bleed the air out by pumping the plunger.