__________________ 1st rule of yachting: When a collision is unavoidable, aim for something cheap.
"whatever spare parts you bring, you'll never need"--goboatingnow
"Id rather drown than have computers take over my life."--d design
do you think yours could be similar to this: http://www.cruisersforum.com/forums/...re-145315.html
i just rebuilt mine, and all's well now. in any case you can isolate the pump from the rest of the circuit (plumb the in hose into a jug, and the out hose to a closed valve - i doubt you can hold 40 or even 20 psi with your thumb, although who knows) to localize the problem.
for what it's worth, but hope this helps...