Bad Fuel Sending Unit?
 

Ok guys and gals,
Help here. My fuel gauge only reads 1/4 when full and then when level comes down less than that it appears to work. I changed out the sending unit with a repro and no status change. I jumped a ground to the connection behind the tag leading to the gauge and it reads empty. I connect it back up 1/4 tank. I unhook it and it goes way past full. It appears my gauge works. I jumped the ground from the sending unit to the same ground the tail lights use and no change. This leads me to think the sending unit is junk!!!

Sounds like you did what this says with the same results.

There are (2) wires that "disappear" on top of the tank to the sending unit. There is a black wire--the ground that needs a good sheet metal ground under the car, and a tan wire that sends the signal back to the dash.

You need to find where the tan wire unplugs from the rear trunk harness. Take the end that runs back into the car and ground it to a good ground. Have an assistant turn the key to "ON". The gauge should go to "E".

Now leave both ends of the Tan wire loose with the key in the "ON" position. The gauge should go way past "F".

If this checks out, the gauge is GOOD.

If this doesn't check out, it doesn't necessarily mean the gauge is bad, you could have an issue with the wiring between the sending unit and the dash.


Try this, need to disconnect the tan wire to the sending unit to check.

Do a Ohm check on the fuel sending unit with a digital multimeter set @ 200.

When the tank is empty it should read 2, at half full 40, and full 84-88 Ohms.

Grounds are important and it's possible it could be the wire between the gauge and the sending unit.

Still no luck. I'm going to try a different brand!

On the back of the gas gauge there is a resistor I found out that the resistor is bad but I can't find a new one . If anyone out there has a old Malibu dash, I would love to get the resistor off of it