We've got a husky power washer hd1300. It stopped putting out pressure. I ordered the rebuild parts for it. Their parts diagram wasn't clear and their help department isn't easy to reach. After rebuilding, it still isn't building up pressure. I tried testing it with the sprayer detached and there's no water pressure coming out from the pump. (The water flows out like a regular faucet with very little extra pressure.)
You might try your question over at the PROFESSIONAL site........www.painttalk.com. They have a PW forum where some experts could help you out. My experience with PW's is that the pumps inevitably go bad after a few years of service. Usually it costs more to replace the pump so I just buy a new PW.