My car hasn’t been run in 10+ years, so… I’m in the process of updating my entire fuel system in order to both rid the car of plastic and aging/leaky hoses. I am starting out at the fuel tank by pulling and completely cleaning it with cleaner, etch, and sealer (using a POR-15 kit).

My question is this: once I have the tank disconnected from the tunnel lines, is it possible to test the fuel sender by simply filling the tank with water? I’m not sure how the resistance of the sender works, and know that some of you will.

Thanks.

remove the sender and turn it upside down. Tank sould read full. Turn it right side up, and the red light should be on.

If you want to test it, remove the sender, insert it in a container with gas. . the further you put it in, the gas gauge will rise. .
I wouldn't put water in the tank. . . or put the sender in water. . just on principle. . may work but why introduce water somewhere it could cause trouble. .

You can also use 91% Isopropanol (rubbing alcohol). About $4 for 2 tall cylinders at Walmart in the pharmacy. Virtually eliminates any moisture concerns and is an excellent contact cleaner and old gas varnish remover...

Dries quick and leaves no residue. NOT 70%!!, only 91%...

Used it for years.

it is very dangerous to use water in a gas tank, both hydrogen and oxygen are found in water. Hydrogen can explode when around oxygen. Water can also be a toxicity hazard in high concentrations.

besides water is very hard on the metal tank, and gauge float assembly, and water is difficult to remove. test the float in a smaller container like a bucket, use alchohol as suggested, or I've used paint thinner, and even gas to check that the float floats. You can dry bench test electrical function letting gravity do the float movement as suggested prior. Keeping the water out of the fuel system is the best advice