[Bowtie67]

Actually if I remember right because I just installed all new guages and wiring in the truck and before I had hooked up the wiring my sender read empty. You can disconnect the wire from the tank unit and see where it is and if it is still reading full I would say a short in wiring, you could also clip the wire as close to the sending unit as possible leaving room to be able to reconnect wire after and try running new wire to tank. Or instead of clipping wire use an ohm meter between gauge wire (disconnected) to body with the wire also disconnected from sending unit and see if there is a short, if no short check wire with ohm meter to make sure its not broken.