VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Gas Tank Sending Unit

Yesterday, I toke my 1939 Chevy on a trip where I used a couple tanks of gas. My gas gauge would not show more than 1/4 tank after filling both times. Later I checked the gauge with a 30 ohm variable resistor and it works fine. So today I removed the tank and the sending unit resistor is also good. Reads 0 to 30 ohms and is smooth as the float is moved. BUT..... the cork float seems to weight a LOT! Probably saturated with gas. I looked at Chevy's of the 40's and they sell a new cork unit, a brass float and a plastic one. I'm sure the cork one would work and most likely so would the plastic one. I like the idea of a brass float, but I'd have to bend the float lever and solder it on. Before I order a float, has anyone any experience or preferences with these floats. Thanks Mike

Just tried to remove my old cork float from the sending unit. It disintegrated and I had a hand full of what looked like wet saw dust. I'll definitely need a new one. Mike

Personal opinion but look how long it took the original float to go bad. If it's a direct replacement I'd go with the cork float.

That's true. Do you think today's replacement would be as good as the original. Some are and some are not. That's why I'm thinking brass. Mike

I use the brass rounded end cylindrical floats. It is necessary to bend the wire in 3/4 of a circle to hold the float. The wire will break if just bent. So I heat the wire to red and allow to cool before trying to bend it. Also have replaced the wire with piece from a wire clothes hanger. Right diameter and stiffness.

I have tried coating cork floats with the same sealer for gas tanks. Didn't hold up even though I coated them with more than one layer. Addition of ethanol makes cork questionable as float material. Shellac was used a cork sealer but it is not compatible with alcohols.

Today, the brass float from Chev's of the 40's came in the mail. The float arm is kinda hard, so I heated it to a red and let it cool slowly. I could then bend it easier. I straightened out the arm and then bent it around 7/8" socket to fit the brass float. Then cleaned and tinned the wire. The brass float was also cleaned and tinned. I had the wire tight around the float and then with a 300 watt iron, the wire and float were soldered together. The float works well, the resistance is a little jumpy, especially near empty, but it works to my satisfaction. Thanks for the help. Mike

Glad your float replacement went well. I found the brass float a good replacement for the original cork.

Keith Knox posted this link about a year ago. It is well worth reviewing. The importance of grounding the tank has been continually brought up by several chat members, and is also stressed in this link. Trouble shooting Gas Gauges by Randy Rundle.

Good luck, Mike

P.S. Also do a search of past posts using the terms +sending +unit

Good article. Grounds are very important in an old vehicle. Seems like a zillion years ago when I first started to work on this car, I made my own wiring harness for it and I included a ground wire for each device. That way I do not have to rely on the chassis and body for a ground. I also added a large ground strap to the engine near the starter. This helps the starter to spin better. Mikw