Thanks guys. Let me clear up some of your questions.
When I say it won’t pump up, I mean that it will lot pump fuel to the carb when pumping the plunger. (although I do have my pressurized “test Tank” that does “pressurize” the tank. I know this because it pumps up and I can then loosen the cap and it hisses to equalize pressure.
I have checked the check valve by taking it off and sucking and blowing into the tube. I have also replaced the check valve with a known good tank and got the same result.
I have checked the gasket in the cap and it is not dry rotted, rock hard, or missing. I “think” it is ok.
Also, I have attached the tank to a motor (in order to see if the connector is leaking) and I could not get it to pump fuel to the carb. (no fuel fills the glass bowl).
This is why I was asking if the diaphragm is different for the new versus old tanks.
