This is a manual for a 1951 Model B, yours will be similar,
http://www.tocmp.com/manuals/Carbs/Rochester/B/1951-B/MCarbRoch1951-B_0007.htm I copied the page about the pump system. I suspect your check ball (#5) is stuck, not letting fuel into the pump well. When carbs set for a while, things tend to stick, even rebuilt ones. Even a well worn leather diaphragm will squirt a little fuel.
Joe
