Thought I'd share a quick easy way to test the tank.

Home Depot sells a 3" expandable pipe plug. Install this in the fuel inlet, palce a small section of 3/8 air hose on the fuel outlet. Install a valve stem in the other end of the hose and hose clamp both ends of the air hose of course. Air up a SHORT blast of air and spray liberally with soapy water. I know this is common sense but finding a plug the exact same size as needed for the filler was a blessing. Total cost: About 4 bucks. Total time: About 15 minutes. Mine was leaking at the old 24volt sending unit gasket.