i have a 2001 f250 with the 5.4. from what i have read i should have the 38 gallon tank. i have been really questioning the accuracy of my fuel gauge on empty with the light on 25 gallons and the fuel pump will click off and after i drive i can park and my fuel gauge will read lower than what it was when i pulled into the driveway with. me and the wife went driving yesterday and we pulled back into the driveway on half a tank this morning i went to go run some errands and when i started the truck the gauge was almost on a quarter of a tank my driveway is flat and after driving for about 35 mins the gauge was still in the same spot and did not move up nor down.
i have a locking gas cap cover so i know someone is not taking gas out. i have changed the fuel filter and tried numerous different fuel system cleaners to try and see if maybe the contacts on the float in the tank are dirty nothing has changed or gotten any better.
i have checked the wire harness from the top of the tank and followed it up under the hood and found no drop in voltage or cracked or damaged wires. i checked with my multimeter i used my fluke meter not some cheap one. i know it makes a difference im at a loss guys.
i have no idea if the gauge is reading less or more from getting gas i am thinking it is showing less than what is in the tank.
any ideas on what could be my problem?

 

Do you have a long box (8 ft) or short box (6.5 ft) ?

(Long box= 38 gal gas tank , short box smaller gas tank )

 

2 door long bed

 

Sounds like a sending unit issue to me, my 07 E350 had that issue where I would fill it up, and the gauge would read 3/4 and very very slowly creep to the F mark. I dropped the tank and replaced the pump assembly and all has been well ever since.