Master cylider question

[911Etarga]

I am so close to giving up on this thing.

I put a new Master in my '71 then bled and bled, but my brake pedal would still go to the floor unless I pumped it several times. Then I would let it sit for 5 seconds and the pedal would go to the floor again. So I returned the Master cylinder and got another one from the same company on Ebay. I just installed it and it is still not working!!! The only time the the pedal feels like it should is when the pressure bleeder is on, pressurized, and all the valves are closed. But when I let the pressure off the bleeder, the pedal goes to the floor. I pump, it gets hard, I let it sit, it goes totally soft.
Could the company (Foriegn car parts, FCP) have a batch of bad masters?
My brakes worked before I did all this but where spongy.....
I have checked for leaks-non.