If your fuel gauge is reading empty when you know there is fuel in the tank, the cause may be a faulty sender unit (the fuel sending unit) located in the fuel tank. This part is relatively inexpensive and can be replaced with simple hand tools. (2) Step 1: Disconnect the Battery Disconnect the battery by loosening the terminal clamps and lifting them off their posts. Step 2: Open Fuel Tank If your vehicle has a locking gas cap, use your ignition key to unlock it. If it has a non-locking cap, twist it one-quarter turn counterclockwise to loosen it, and remove it by hand. Carefully lift up the cover of the fuel filler and place it somewhere safe where it will not get damaged or dirty. Step 3: Remove Fuel Pump Access Cover Remove any screws or bolts holding down the access cover over the fuel pump module. There may be several on some vehicles, so check all four corners of the panel for fasteners. Once all fasteners are removed, pull up the access panel to remove it and set it aside for later installation. Step 4: Remove Old Sending Unit To remove the sending unit's electrical connection, first, unscrew all screws holding down the ring around its top. You'll need to use a deep socket or a similar tool.