Loss Of Fuel Pressure

If the fuel tank vent lines are plugged (or capped) then yes, as the car runs and the fuel level drops, it creates a vacuum in the tank, eventually matching the suction from the pump. Run it until it loses fuel, then pull the cap. If you remove the cap and get a sucking or whooshing sound (like opening a jar) then it has aventing issue. I see it more commonly in post '72 cars with the vent sytems they had. I even capped a line once thinking the other vents were clear, and got myself stuck the same way... and that is with a big electric pump...lol. Also, sniff your oil to see if it's contaminated with fuel. If the diaphram in the pump leaks, it could be going into the crankcase. You'll smell it and the oil will be very thin if that's the case.