The Stovebolt Site Forums The Shop Area The Electrical Bay Gas Gauge Problem

I just installed a new gas gauge, sending unit, and tank in my 1953 3100. Its a 12V system. The gauge does not work as it doesn't move from empty. I want to confirm how the gauge is wired. What side of the gauge does the sending unit ground hook up to and what side does the ignition? I thought my gauge had a positive and negative on the back but I'm not sure since I can't see it without taking it back out. Thanks for your help.

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Sometimes the new gauge needle will pinch on the bezel. Check to see it is clear.
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Also make sure the gauge itself is grounded to the housing
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Yes, before I installed I made sure the needle was clear and removed the paint for a good a good ground. I'm thinking maybe I wired the gauge wrong between the ground and the ignition. Is that possible?

On my truck the sender grounds to the bottom of the cab
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Not sure if it's the same on your year

The gauge will have an ignition terminal (switched 12V) and a sender terminal and I believe is grounded by the case/mounting. The sender should be also grounded from one of it's mounting screws to the frame. This is a must have wire, otherwise you are relying on straps, tubing or touching, not good. Wire brush the sender flange, screw and a nearby spot on the frame, install the wire and then cover all the bare spots with that liquid insulator. Be sure the frame is grounded to the body and body to engine. It all should be checked for operation before final installation. The same careful grounding should be done at the gauge(s).

If you have a simple test probe with a light you can test the power side of the guage and make sure you have power. If you then touch the sending unit side of the guage the guage should move. I know it's difficult to get to while standing on your head under the dash so you can do the same by probing the wires that connect to the guage.

You can also test the fuel sending unit with an ohm meter. It should read between 0 and 30 ohms.

ok, thanks, I'll give it a try

There is great help on this in Tech Tips.

Ok, I pulled the gauge and the problem was that it wasn't grounded properly. With the sending unit out of the tank, I moved the arm up and down and the gauge worked properly. However, once I mounted it to the tank it would not work. The needle stayed on empty when the tank was 3/4 of the way full. Is this a bad sending unit or do I need to try bending the arm? This is strange it would work properly out of the tank but not when its inside of the tank.

Hi, 53, It sounds like you have the float arm indexed wrong. If you have the in cab fuel tank you should have the float arm facing the side of the truck. If it is facing the back or front it will hit the tank and not move. If it is like a boat sender you can unbolt the center bolt , lower the sender and rotate 90deg and then bolt it up. Hope this helps. Have fun, Brian

Does the float float? You could ohm your sensor to ground to be sure the ground is good.

Thanks Brian, yes, I made sure the arm was facing the drivers side of the cab. I also did a test in a bucket of water and it worked fine. As I mentioned, it worked fine when its connected outside of the tank which tells me it has to be something in the tank. I believe these are 19 gallon tanks so maybe I just don't have enough gas in the tank. Its about half full right now.

Hi, 53, Check the length of the sender float to the mounting flange out of the tank in the empty position and with the sender out of the fuel tank, check how deep the tank is. You may have the wrong sender. You want about 1/2" clearance of the float above the bottom of the tank at empty.