When I turn on the ignition my fuel tank registers as full, even though I know it is empty (I have just drained it). How do I identify if the problem is in the gauge or the sender unit? The sender unit has both live and earth wires. Should the unit itself be insulated from the tank body?
to test ..disconnect wiring from tank unit the needle in the car should go to empty. put a wire to both terminals on the wiring plug..(jump wire)..and ign on needle will go to full
if when by passed with wire the guage reads full then the tank unit is at fault...sounds like the tank unit has got fault and is shorting out and making your gauge read full all the time
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.