Here's another thunk from a recent experience.
If the fuel line hoses are old, you could be losing suction from the pump.
I could blow through the hose that went to the pump inlet and hear bubbles in the tank (checking for obstruction).
I still couldn't get the pump to deliver.
I pulled a section of hose, crimped one end and blew into it and air could be heard... though it wasn't leaking.
I replaced it with new hose and problem was solved.
Jerry
