You don't seem to be getting anywhere here. You are looking for someone
to provide a quick solution and you won't find it at your computer
without doing something. Get up, go out there and check things. I think
your old pump is dragging and blowing the fuse. I would be persuaded
differently if you found something else on the circuit with a short
causing the current draw. But the pump is probably old and very
suspect. They do go like this. If that is the case it's a big job to
change it. I would put an amp meter in series with the pump and see
what it draws. It should only be a few amps. If it's close to 10, you
need a pump.