I have a 1964 MGB that had a original SU fuel pump that worked fine for years after I cleaned up the points. I did leak very slightly so I decided to replace the stiff diaphram and points with new parts. I set the points as per the manuel and unscrewed the diaphram until it just flipped over and then one more turn. Seemed to work fine at first, but stops at times and leaves me sit. Let the car sit for a half hour or so and it runs again. I tested with the pump out of the car and can get it to stop by placing my finger over the suction inlet. I can even remove my finger and it still wont pump until I shake or hit it. Any ideas why??? Thanks