Since I don't have a set up like yours so I can't say for sure, but the accummulator when it gets its pressure and builds up seems like it might have a check valve[whether piloted or manually released] that holds that pressure and when you cut off the machine it relieves the pressure on the check valve. If it has a check valve then that check valve could have something holding it open and letting it just pump oil straight through it and back to tank. If it has a check valve and it is stuck open then that would cause the problems that you are having. Just thinking out loud without looking at the system that you have, I'm probably wrong about that thought but then again I might be right, and then again who knows [Terry].