2001 Ford V-10 Gas Guage

I had a similiar problem with a 1989 E350 Ford van except that it would show empty all the time. Turned out to be a brass float for the fuel sending unit that had a hole in it and the float filled with gas. Dropped tank, removed sending unit and float, bought new float for about $10 and reinstalled.

99% of the time, on a rig of that age, it's the sender. Most shops don't even trouble-shoot, they just replace the sender.

Unfortunately it seems like most of the time Ford makes your drop the tank to replace.

Two people. One inside cab manning ignition switch and watching gas gauge. You underneath rig with 12 volt test light, clipped to shined-up chassis frame ground.

ONE of the wires going atop the tank is the fuel gauge wire. Turn key on, probe each wire and when partner says "That's It!" the gauge rises, then you either have a bad ground (unlikely with gas tank fuel pump) or a bad tank sending unit.