Gas Gauge Sensor

September 25, 2005 to October 22, 2005

Let me start by admitting that the damn gauge worked when I started this project. It does not now. Anyone see where I went off the reservation? I sure don't.

When I took the sensor out of the tank I could not believe it still worked. It looked like a solid block of rust. This is also a pretty fair sample of what the inside walls of the tank looked like as well.

I was almost in shock as I started cleaning. I carefully removed the gunk and rust with a toothbrush and a brass brush. Spray-can carb cleaner helped loosen the bad spots. The float was in good shape but a little dry-rotted. To try and preserve the whole thing I painted everything you see here with the tank sealing compound when I coated the tank. I hope that painting that cork was not a really bad idea but I figure it can only help hold it together at this point.

Here is the top with the cleaned electrical contacts. Notice the three rivets holding the sensor together. Guess where this is going...

The old tank wiring harness was in bad shape. So I made a new one. Once the harness was assembled I tested it then tried to test the sensor with a multi-meter. Imagine my surprise when it did not seem to be working. Wiggling and shaking would get me continuity though one of the two terminals but the other never seemed to work.

At this point I was out of ideas so I reluctantly drilled out the three rivets holding the sensor together.

Here is the resistor part of the sensor. The wiper attached to the fuel level float shorts this to ground to vary the resistance between each terminal and ground. This guy looks to be in good shape.

And this large picture shows the other side. Click on it for a close-up. The float lever passes into this area though two insulated bushings that also position the wiper relative to the resistor. The end of the lever bends about 90 degrees and is crimped to a bit of brass bent and shaped to form the wiper on one end and a ground contact that rubs on the body of the sensor on the other.

The first problem I found was a hole in the wiper where it rubs against the resistor. The brass just wore through. This fuzzy picture shows the hole.

I carefully cleaned the contacts points and tested the sensor. It seemed to be working OK so I started thinking about putting it back together.

I found new rivets at the hardware store. I also made a minor modification. Since was doing everything in my power to ensure there was no bare metal anywhere on the gas tank I figured I might have a problem getting a good ground on the tank after putting it back together. After a little rooting around in my boxes of electronic bits I found a ground tab that I could scavenge. Here you can see the ground tab riveted on with the top rivet. I used a hammer and a steel rod to mash the rivets. They will work but did not turn out all that well. If I ever have to do it again I will mash them with my vise.

The gasket between the sensor and the tank was in pretty bad shape so my oldest daughter Rachael helped me cut a new one. She took the picture at left.

Using the new gasket and some sealer I re-installed the sensor in the tank. I hooked up the new harness and ran a ground wire from the ground tab to the frame. But the gauge is always empty now...