Fuel gauge inop?
 

Picking up a 01 F-250 and the fuel gauge is inop the low fuel light works so I was wondering if anybody has a good starting point? I'm new to diesels as this will be my first had mostly Yotas and one Dodge 1500 thought it was time for a real full size.

Thanks

does the guage stay on empty, or does it go to full and not go down.
If it goes to full and doesnt go down, it is probably a ground problem, if it stays on empty, it is a problem on the power side of the circuit or in the tank sender unit.

do you have an ohm meter for testing?
a common problem is that the sheet metal nut will fall off of the float and then the float will fall off causing the gauge to stay at empty

Yea the needle stays on empty, now I am assuming I have to drop the tank to get to the float I guess it won't be to bad if its empty and I get some help.

So filled the truck and fuel gauge went to full for a few minutes then slowly went to empty so I am thinking sending unit.

usually when the sending unit goes bad it will stay on full due to high resistance, since it stays on empty i would think it would be the float or the signal wire shorted to vref

I'll check the wiring first since it was working yesterday then took a dump again.

Wheres the ground wire? my harness only has two wires from the tank. My guage stays at full most of the time but occassionally goes down to where it should be.

The sending unit has two wires a ground and a hot. it is possible that one of the wires has come off sending unit. if it is staying on full.
if it stays on empty more than likely the sending unit is bad