The problem is the mechanical pump is bad or the lobe on the cam is worn off enough the pump arm is not moving. As for the electric pump, put a momentary push button in line, use it only for priming the carburetor, there's no reason to run it full time. See if fuel will siphon from the tank to a pan lower then the tank. If it does, your mechanical should be able to pull fuel through it and work as normal.
