This is a Sears 2700 psi washer, it's several years old with a B&S vanguard. The engine runs ok, but the pressure won't kick on. If I fool with the throttle and rev it up past where it normally runs, (over riding the governor) I can play with it and get it to engage. And it works fine until I let the trigger off the pressure gun, then it won't engage again until I fool with it some more. It's like there is some kind of clutch in the pump that's stickey.

I'm pretty good on fixin' engines, but have never done anything with a pump. This belongs to my brother in-law so I really don't know the history, but I would like to use it now that I've borrowed it. He said he'd had the same problem.

Any thoughts on what the deal might be? What about rust build up on the pistons causing them to hang up? I doubt if he was very good at preventative maintainence.

sounds like the valves inside the pump are stuck

that does sound plausible, bet they are rusted up. There are a number of removable caps I'll try getting into those and see what turns up.