Otto
Here's what I'm talking about on how to check the cam lobe. But I don't think you'll find it to be a problem.
What you're describing sounds like an inlet check valve in the pump (both of them - It's not the first time that a part has been bad out of the box) stuck in the open position or leaking enough that it pushes the fuel back into the tank instead of up to the carb.
You can get a repair kit for the original if you want to use it from Then and Now Automotove
Link. Fuel pumps aren't that hard to repair. I did that on my original glass bowl pump and they even include the strainer that goes on top in the bowl.
