The most likely place is at the pickup base in the tank. It could also be at an elbow or connection. It could be in the middle of a fuel line, but it's unlikely.
Have you replaced your Racor filter? If you had bad fuel, you may have to replace it 2 or more times.
If you buy the right size hose, temporarily hooking up a ball pump should be quick and easy. Just push the hose on the nipple. Start at the tank, test each section, and move down the line until you isolate the problem.