First, check to see that the camshaft lobe that operates the pump isn't worn out. Remove the pump, and have someone tap the starter as you shine a bright light into the hole. There should be a noticeable high spot visible as the cam turns. If the shaft is round, or showing extreme wear, it's time to change the cam. It's also possible you've simply bought a non-functional new pump. Push the pump operating rod down against the workbench top and see if any vacuum is developed at the inlet port. It's either a bad cam or a bad pump, or possibly both, but that would be pretty unlikely!
Jerry
