Peggy, I have a 9 year old Jabsco toilet. A few months ago, I got a package with parts for rebuilding the pump. There wasn't anything really wrong with it except the rubber valve(s) pad that sits on top of the pump and switches from wet to dry mode had a small tear. Now that I've installed the new valve pad, the pump locks up in the dry mode after serveral strokes. It feels like there is a pressure build up in the cylinder, similar to trying to pump in the wet mode with the thru-hull petcock closed. If you flip the lever from dry to wet and back, the pump works again for several strokes then locks up again. Any suggestions? Bill