I have a replacement fuel tank for my car and was going to install it shortly. Is it a good idea for piece of mind to replace my sending unit while i'm at it? The one i have in my old tank is a minimum 16+ years old.What exactly does the sending unit do? Is it just a float and reading level kind of funtion it performs or is there more to it than that? If the float sticks or does not function properly what happens? Will the fuel pump still be able to pump gas if the sending unit is faulty?

David

The sending unit reflects the amount of gas in the tank. At a minimum, replace the sending unit gasket and the filter screen. You can test your sending unit with an ohmmeter when it's off the car, or if the rest of your electrical system is intact you can hook up the sending unit and raise and lower the float to check the indicated fuel level.

The mechanical fuel pump is entirely independent of the sending unit, other than the fuel passing through the pickup tube.

Thanks Vikki. I was just wondering if it was stuck above the fuel in the tank, would the pump still be able to pump the gas.

David

I would say replace the whole thing David. I had my tank out this winter for some metal work and decided to replace the unit just for piece of mind.
The float should read from 0 to 90 ohms when you’re testing it.
Oh, and be sure that it sealed properly before you put the tank back in. Put some Vaseline on the gasket and make sure the ring didn’t pop out anywhere. I did mine and it leaked really bad. When I drained and pulled the tank again, I noticed that the ring had popped out under the line and I didn’t notice it.
To leak check it, just create a nice tight seal with your mouth on the filler neck and blow (I know the comments are coming for this one ). It will take a couple breaths but it works.
If you don’t replace the whole unit, defiantly replace the ring and screen as Vikki said.