Hard start under 1/2 tank. Replaced a lot of parts!!

[Big Del]

Hi my truck is a 90 7.3, it won't start under 1/2, the closer it gets to half a tank the longer it cranks before starting. When I get it started its fine the rest of the day. It will run the tank empty if I'm on a road trip with out any direvability issues but if it sat over night that low it won't start.

I did a cup, return line and O ring kit and it didn't fix a thing. I dropped both tanks and the tanks and pickups were in perfect shape, so were the hoses return and supply. The lines were hard to see and the clips were brittle and 1 tab was broken so I put new keepers on thinking-hoping that would fix the air intrusion... NO GO, I'm getting frustrated filling it everytime it gets close to half.

I also put new fuel filter with pet****, pickup pump and I don't see any visible fuel leaks?

[91fordoilburner]

Put and electric pickup pump inline after the tank switch, 60 bucks at parts store should help greatly