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Discussion Starter #1
recently my fuel gauge began to not function, it stays on full.
i searched and read some others with same problem, i checked the ground on both ends and cleaned them up, no fix.
Also read from Jim on this site to took apart wire in back trunk area, grounded out the wire coming from the gauge still stays on full.
what else can i troubleshoot before dropping the gas tank?

At this point, would it be leaning toward a faulty gas tank sending unit?
 

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1972 Nova
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If grounding at the trunk connection doesn't bring your gauge to empty, I would start looking forward rather than back towards the tank. If you grounded the car side of the connection and the gauge went to empty, that would mean the issue is at the fuel sender or around there. Can you find the wire right at the dash and try grounding that? It could be your fuel gauge acting up.
 

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Discussion Starter #3
If grounding at the trunk connection doesn't bring your gauge to empty, I would start looking forward rather than back towards the tank. If you grounded the car side of the connection and the gauge went to empty, that would mean the issue is at the fuel sender or around there. Can you find the wire right at the dash and try grounding that? It could be your fuel gauge acting up.
the wire at the dash, what color is it? where does the ground wire connect at the fuel guage?
 

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I agree with sudden_impulse ... if grounding the wire at the connection point in the trunk didn't cause the gauge to read empty, the problem is likely somewhere forward of that point.

The wire connecting the gauge to the sending unit should be tan along it's entire length.

In addition to the connector near the back of the trunk, the tan fuel gauge wire passes through 3 more connectors on it's way up to the gauge.

One is located in the forward part of the trunk, up over the driver side wheel well. It's a 6-cavity connector with 5 wires (one empty cavity).

The next connector is located up under the dash. Above the driver side kick panel, near the parking brake pedal assembly if I remember correctly. It's a long rectangular 11 cavity connector with 8 wires. The tan fuel gauge wire is near the middle, right next to a couple empty cavities.

And the final connector is located right on the back of the instrument cluster.

Working from the back of the car forward, try grounding the tan wire at each of those connection points. If the gauge goes to empty, you know the problem area is somewhere between the current & previous test points.

If the gauge continues to read full (even when grounding the tan wire right at the cluster plug), the problem could be the terminal in the cluster plug not making good contact with the finger on the cluster's printed circuit, a break in the printed circuit trace, a poor connection where the fuel gauge stud terminal connects to the printed circuit, or a bad gauge.


The fuel gauge grounds through the metal instrument cluster housing. And since the housing is mounted to a plastic bezel, there is a single ground wire (separate from the cluster plug) that connects to the cluster. However, a bad ground connection at the gauge will typically cause it to read empty (opposite of what you're seeing).
 

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Discussion Starter #5
I agree with sudden_impulse ... if grounding the wire at the connection point in the trunk didn't cause the gauge to read empty, the problem is likely somewhere forward of that point.

The wire connecting the gauge to the sending unit should be tan along it's entire length.

In addition to the connector near the back of the trunk, the tan fuel gauge wire passes through 3 more connectors on it's way up to the gauge.

One is located in the forward part of the trunk, up over the driver side wheel well. It's a 6-cavity connector with 5 wires (one empty cavity).

The next connector is located up under the dash. Above the driver side kick panel, near the parking brake pedal assembly if I remember correctly. It's a long rectangular 11 cavity connector with 8 wires. The tan fuel gauge wire is near the middle, right next to a couple empty cavities.

And the final connector is located right on the back of the instrument cluster.

Working from the back of the car forward, try grounding the tan wire at each of those connection points. If the gauge goes to empty, you know the problem area is somewhere between the current & previous test points.

If the gauge continues to read full (even when grounding the tan wire right at the cluster plug), the problem could be the terminal in the cluster plug not making good contact with the finger on the cluster's printed circuit, a break in the printed circuit trace, a poor connection where the fuel gauge stud terminal connects to the printed circuit, or a bad gauge.


The fuel gauge grounds through the metal instrument cluster housing. And since the housing is mounted to a plastic bezel, there is a single ground wire (separate from the cluster plug) that connects to the cluster. However, a bad ground connection at the gauge will typically cause it to read empty (opposite of what you're seeing).
thanks for your time, i’ll spend a couple hrs testing the tan wire from trunk forward tomorrow ...
 

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Hey Julie,
I see you had some other electrical issues last year. What did you find on this one? I note it's a TAN wire being discussed....
 

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recently my fuel gauge began to not function, it stays on full.
i searched and read some others with same problem, i checked the ground on both ends and cleaned them up, no fix.
Also read from Jim on this site to took apart wire in back trunk area, grounded out the wire coming from the gauge still stays on full.
what else can i troubleshoot before dropping the gas tank?

At this point, would it be leaning toward a faulty gas tank sending unit?
Do you have a copy of the service manual? There are some hints in there if I remember correctly. I had similar problem last year and found the connections to the fuel gauge and the ground point bad. I drilled a new hole and set ta new ground point, cleared the problem. If it makes you feel better I am in the process of replacing all the wiring harnesses. They are all painted over (black). Some are cut and left live, others are spliced and going to God knows where. The best investment you can make are the manuals. Year One, Ground Up and Eklers all have good stuff. I also use Summit and Jegs
 
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