I got a "made in Canada" fuel pump like you describe to put on my big bore
engine when I built it up for my 122 wagon in Panama. It lasted less than
3 weeks before something broke inside, I believe the actuating trigger.
I was about 3 miles from home so I had to blow in the gas tank to fill the
carbs, start it and drive it till it ran out and then do it again. Good thing
I wasn't any further! Have you noticed where the gas cap is on a 122 wagon?
Mighy LOOOooooooow! And since the tank was full it belched about a quart of
gas on me each time I stopped blowing.

I'll stick with a new Pierburg pump from now on! If it is good enough for a
good-breathing 164 it'll certainly handle any B20!

In response to your question, though, you certainly have a leak on the suction
side, but whether it is in the pump, the line or the pickup in the tank is
hard to say. Could be any of the above.