How do I fix a 1989 Toyota corolla Fuel gauge that indicates empty all the time even when full?

Answer 1

You will need to determine it to be 1 of 4 things. 1: Broken wire between guage/dash and fuel tank. Typically you will find the wire breaks under the car, or along the edge of the door trim, where usually it is close to foot traffic and rubs and/or breaks. 2: Blown guage fuse, but this would usually affect temp guage as well as other indicator lights/guages. On many vehicles also the guages run off a voltage regulator, that could fail, but again other guages would be affected. 3: Sender unit inside the tank is stuck. This is easy using an voltmeter to measure the wire going to the sender unit. If you had filled the tank, the voltage would be very low, typically less than 1 volt, and the guage would be at or near maximum. Without removing the tank, you will simply need to measure it with the key in the on position, then drain the tank, safest way possible, usually by disconnecting the fuel line under the vehicle where it goes into the fuel filter. You may need to jumper across the fuel pump relay (if it is an electric fuel pump) to force the pump to drain the tank into a gas can. Then once you have removed the gas, measure once again the wire from the sender unit, and it should read a higher voltage, usually around 8-10 volts. 4: The guage itself is bad. This is easy to check, by simply grounding the wire from the sender unit and the guage should rise to full and then remove the ground and the guage returns to empty. If it does then the sender unit may be defective, and you are now faced with removing the gas tank from the vehicle, and replacing the sender unit. If your not familiar then my best advice now is to take to a garage to do this, as it is a very risky procedure, and you could easily blow yourself up, to death or severe injury if your not careful in removing the sender/pump unit from the tank.