Two main components make up a vehicle's fuel gauge system: the fuel gauge that shows how much fuel is present, and the sender unit that actually measures the amount. If one of these components isn't functioning correctly, your fuel gauge may not work or it may display inaccurate information. If you suspect your fuel gauge isn't working, you will want to test it.
Turn on the ignition and turn it off a few times in succession. Check to see whether the fuel gauge needle moves. Check the fuse if the needle doesn't move. You may find the fuse panel either beneath the dashboard or beneath the bonnet. Replace any bad fuses.
Attach one end of the jump lead to the terminal behind the fuel gauge. Attach the other end to the ignition. Turn on the vehicle. Replace the wiring between the ignition switch and the gauge if the needle works when doing this.
Disconnect the attached wire from the sender unit to the fuel gauge. Turn on the vehicle. Replace the sender unit if the fuel gauge claims to be full. Replace the fuel gauge if the needle doesn't move.