doc93

Anyone ever had thier fuel gauge read full all the time? Or how can I test the fuel gauge?

Tedd Thompson

Doc93, does your gauge go to empty when key is off? If it does then I would look at the sender in the tank .The float could be stuck in the tank at the full position due to crud,rust ect,or it is shot from old age. Before you drop the tank check to see if there is current to the gas tank sender. It should be gray and can be found, I believe,at the rear trunk area near the license plate lead.If no juice there you have a broken wire or bad connection. If you drop the tank check the leads to the sender and test for juice at that point.I would also reground the tank to see if there is a broken ground some where. Keep an eye on the cluster gauge to see if you get movement at any test.The fuel tank guage is nothing more than a rheostat and the cluster guage a meter that reads restance.Hope this helps...Tedd

jaunty75

This is typically a symptom of an open circuit in the fuel gauge wiring. Ground the gauge, and it should read empty. Open circuit should read full (or well beyond full). Trace the wire from the tank as best you can (it might be hard to get at right where it attaches to the tank sending unit as that is likely to be on top of the tank, I would think) all the way to the gauge and look for a break in the wire or an open connection.

To test if the gauge itself is working, find the wire coming from the gauge, disconnect it from the end coming from the sending unit somewhere (there might be a connector somewhere around behind the rear license plate area), and ground it. The gauge should go to empty. If it does, the gauge is ok and you have either an open circuit or a problem with the sending unit inside the tank. With luck, it will just be an open circuit.

55miketn

the 55 ground wire (grey) is mounted to the sending unit and is covered with a leather strap to protect it. If it is not making a good ground,(open circuit) then it will read full any time the switch is on.. I ran a new ground wire ( the attachment post was loose) and ground it on the body at the trunk floor. I had to solder the post to make a good contact. I pulled the tank and pulled the sending unit. You could just buy a new sending unit if you pull the tank. (I'm cheap)

Olds Dad

I believe there's only ever one (factory) wire to the unit (grey according to the service manual) - and the ground comes through the steel fuel line to the tank and ultimately strapped to the frame. I found this out the hard way by replacing my tank, installing a short piece of rubber fuel line (killing my ground), reinstalled the new tank to find my guage pegged full with key on, empty with key off...I removed the tank again, screwed an eyelet with a ground wire to one of the sending unit screws, ran it through the trunk pan grommet with the gray wire, and to the trunk latch assy...and now I have a fuel guage again...just my experience.

jaunty75

The original question in this thread was posted 15 months ago.

Olds Dad

oh yeah..look at that - I (obviously) tend to not notice the dates...saw it in the "New Posts" and just replied...it's not easy being this stupid

golds56

well i am sort of glad someone answered him ,my tank was renewed about ten years ago and its just been setting since ,i put fuel in and guess what? The darned gauge goes to over full with the key on.Just what i needed another project.

55miketn

If it goes to full when empty, either the float/sending unit is stuck in the up position, or you don't have an adequate ground on the sending unit. Put a jumper wire from the sending unit(clean contact) to a good ground and see if it works(should read empty). If so, the ground is the problem.

golds56

is the sending unit toward the front or back of the tank?

Tedd Thompson

If I remember correctly it's about 4 inches from the front, centered on the tank. It's been 10 years so someone correct me if I'm wrong.....Tedd

55miketn

The sending unit is in the top of the tank left of center toward the front. If you are under the car, you can see it when you remove the fuel line. The bolts that hold it in are supposed to ground it, but if there is a strip if material between the mounting strap and the tank, it will not let the tank ground. That is why I ran a separate ground wire from one of the bolts to a good ground in the trunk. Works perfect!!