If you have any rubber fuel line between the fuel pump and the tank check it real close for any cracks where the pump could pull in air when trying to pull fuel from the tank. I have seen it before as once you get the fuel to the pump it works for a bit but because of cracks in the suction side it bleeds off the fuel in the suction side and wont start again later. You most likely pulled much more vacum with the mighty vac pump the the fuel pump makes so that may be why it worked like that. But I would check the suction lines for small crack. Not big enough to cause a fuel leak problem but enough to pull in air on the suction side. Course an electric fuel pump back by the tank is a good idea. Ron