The Stovebolt Site Forums The Shop Area General Truck Talk Fuel sender float

Think about it. The current from your hot wire goes to your sending unit then to ground. The amount of current going to ground depends on the amount of current allowed through the sending unit. That differing amounts of current is controlled by the position of the rheostat in your sending unit. An empty tank allows nearly full current to pass. A full tank allows little current to pass. Touching your hot wire directly to ground is the same as the sending unit float being in the empty tank position so your gauge reading empty when you do that is not abnormal.