I've had a Serfas floor pump for years now, and of course the gasket in the head was worn out. It wouldn't hold on certain stems, and would always leak as I pumped. I just replaced the head with a new Park one and its like having a new pump. It grabs, it doesn't leak, it takes many fewer strokes, and when I release it, it pops right off without loosing any air.

The funny thing is, the two pumps may very well use the same gasket, especially if it's the one that looks like this:

yea, it's one of those. I just popped off the old one and put in the new Park head. These are pretty common. The problem with them is you can't easily just replace the presta gasket.

Funny you should mention it. I recently wrote up a ifixit guide on how to replace that gasket since I had the same problem.

Never thought it would possible to get it out, but now I see you can. Where were you a week ago? For $7 the whole head was an easy fix in any case.