'68 Barracuda -wire to fuel tank sender

You can do the same thing with the temperature gage. Unplug sender with key on, it should go to cold. Jump the sender wire directly to ground it should peg all the way hot. That rules out a temp gage being a problem. Using this method with both fuel and temp gages also tests the sending unit wires from the gage to the sender for opens or ground shorts to rule those issues out as well.