I've had good luck with polyester fiberglass resin. This is on floats used
with
a wire sticking up to see fuel level.
I have dipped them in resin and then shook off the excess. They don't
seem to float any lower and the resin resists auto fuel.

Cheers:

Paul
NC2273H


Got a pair of fuel-level senders and the cork floats have lost some of
whatever it was that was painted on them. These will be in tanks with
automotive gasoline. What should I use to seal them?