I have had an issue for several months now with the F350. I can fill it up and it reads full. When I drive it the needle drops down and when it hits the halfway mark it goes back to full. I haven't pushed it past that point too much but it's there now. However, I can put about 18 or so gallons in it at this point when it goes back to full on the gauge. I have been keeping up with the mileage on the odometer to know where I am and has been fine but want to get it fixed.

About 10 years ago I did the hutch and harpoon mod on it. I remember putting in a new tank supply return sending unit assembly because I think it was doing something like this at the time back then...just can't remember. I recently did the hutch and harpoon mod to the Excursion because the tank filters were dirty and starving the pump for fuel. I put in a new tank supply return sending unit assembly after cleaning the tank. I still have the sending unit from the Excursion and it wasn't having fuel gauge reading problems.

Has anyone had issues like this? I am thinking it is probably the sending unit but want to make sure before I pull the tank assembly. Also, I know the Excursion has a different size and/or shape tank so am wondering if I can somehow utilize the sending unit from it but don't know if the fuel level arm assembly will interchange.

 

I had a 150 with this issue, in those they used a brass float for the gage, Not sure on the larger trucks,

but ford would try to sell you the entire unit. When it was really an 8.00 fix.....

maybe some one will chime in with recent knowledge.

best of luck

 

The float is a black plastic unit. I looked at the unit I pulled out of the Excursion and the plate the sending unit mounts to is steel, and rusted. Why the rest of the unit is stainless is beyond me! I am guessing after looking there are wiring issues...maybe bad ground because of the rust.