Sounds like M Dew has the right thought. The strainer, we called them the sock, in the tank sounds clogged. When low on fuel it is sucking through the lower part where all the crud is. A simple vacuum test would tell if that's the problem.

ComputerScrapper thats reminds me of the auto parts store years ago. It was called One Stop.
We called it Ten Stop. A few trips just to get the right part then a few more to get one that worked!