The Stovebolt Site Forums The Shop Area The Electrical Bay 1953 AD 3100 Fuel Guage Mystery

I have a 53 chevy 3100 with a 6 volt system. Recently restored this truck with new guage cluster and wiring and fuel sender. My problem is the guage works great outside of the tank. As soon as you put it in the tank with fuel on it it registers to empty. I have read all the forums on this topic. I grounded the sending unit to the cab ohmed the sender read 30 at full 0 at empty checked continuity on all wire connections again and grounds. This is an electrical mystery like I have found a UFO or something. No one can believe this fuel tank can change this reading like this as if we are losing our ground when we put it in the tank. Any help would be appreciated. Thanks John

Does the float on the sending unit actually float when you put it in the tank. Could there be a hole in the float, causing it to sink?

If you have fuel in the tank, the float will float on top of the fuel

Unless there is a hole in the float.

Take the float out and see if there is fuel in it (bad); and/or, see if it floats on water (push it in the water).

Yep! Look for a submarine float...:) They can be bought as a single part so not too bad. They can be soldered if the leak is small and you are brave...:)

Sorry no fuel in the float! Have had that happen on other old trucks. Is there a chance that I have a 12volt guage or sending unit? by accident? Just had the guage cluster rebuilt. The sender is new also. Dont think sending units are 6v 12v specific though.

Sender and gauge are not volts specific. The problem is most likely a ground or bad wire so look at those real well. If it worked on the bench and the float is good you have a connection issue. If you pull the seat back out you can access the sending unit from in the cab. Lift it out of the tank and see if it will work when hooked up and you move the float up and down. Use care, you are sitting over an open container with the tank in there. Let us know what you find.

Mine did the same thing. If I tapped on the glass once installed the needle would move. Something must have put a bind in the gauge when installed and the needle was touching the glass. It worked perfect on the bench.

Gentlemen I went thru all my grounds once more. Decided to take the truck for a ride. No fuel indication. Drove down a rough country logging road for about 20 minutes and the guage came to life. I figure the bumping around finally polished enough metal so my quality of bonding increased. Thanks for the ideas. Now if I can find some speedometer magnates my speedo will be fixed, any idea on where to find those would be big help. Thanks John

Just guessing here....Could you have the wrong sender for your gauge. Most gauges read a higher resistance when empty than full, 30 ohms empty, 0 ohms full. I would hang a variable resistor (pot) on the sender wire,ground the other side and check what resistance it take to go from empty to full.

Went thru whole harness and all ground with multi-meter again. Decided to go for a drive. Guage came to life after a run on a rough dirt road! So I gues the vibration polished some metal and improved the bonding of the grounds. Thanks for all the great input. Now I need to find a set of magnates for my speedo. Any Ideas on where to find these? Thanks John

If your sender isn't grounded, the gas gauge generally will read full not empty. I would pull the sender out of the tank, ground it to bare metal and move the float up and down and watch the gas gauge. My guess is that the gauge mysteriously went bad, lost power, or the needle is hitting the gauge glass as mentioned above.
Carl