1940 Tank Unit Sender
A Technical Tip from Buick Technical Tips

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Tank Sender Unit (1940) -- If by now you have concluded that your tank sender is intermittent, why not rebuild it yourself? I did, and it works just fine.

Siphon gas from tank or run it dry, rinse with water and drain again, especially if you have to use heat on the strap nuts in the trunk well. Use every precaution that common sense dictates when working around gasoline. The tank drain pipe plug is rotted in place and will tear the tank if it is torque too much. (Don't use heat on this item, please!)

• Remove the sender unit from top of tank.
• Put unit on bench and drill out the rivets that hold the cover over the slide wire. 
• Remove the cover and you will see the thin copper flexible strap that connects the slider to the wire lead terminal. It will be broken about in the middle. 
• Soft-solder it together, or solder a flexible jumper wire from piece to piece to restore electrical continuity. 

When you see the problem, I'm sure a number of solutions will come to mind. Make sure that the strap will not short to the case and replace the cover, using a few small machine screws and nuts (#4 or #2, I forget which size I used). Use some RTV or Permatex to seal the cover. If you find the slide wire burned, it is because someone over the years jumped the battery wire to the tank wire on the gas gauge. Most of the time the strap will be broken. (Clean the slide wire with alcohol before reassemble.) 

• Check with ohmmeter or jumpers to ground, and gas gauge.
• Check float for gas logging and make sure float arm does not bind when installing.

Buick Bugle, June, 1988, James Cox, #12125.