This issue just recently popped up but when my fuel level gets down to about 1/4 tank I have noticed that my crank times have been getting longer. My truck starts up fine when its full. The fuel filters are motorcraft and only have maybe couple thousand miles on them. Any ideas what I need to start looking at?

Early 2004 F250 with 270k miles.

 

Install a sensor and gauge on the fuel pressure.

 

The suction isn't sitting directly on the bottom. Your foot valve may have came off, that makes the suction even higher.

Worse case is your causing low fuel pressure and maybe causing injector damage. Fill the tank.

I never let it get below a 1/4... ever!