I have a Sears 1800 psi pressure washer which I discovered has a Generac pump. It required a new head gasket, which had deteriorated and was leaking. I found a website that supplied Generac pump parts by typing Generac pumps in the Yahoo search engine (I can't remember the name of the company).
Although I had to wait 2 or 3 weeks, they did ship the replacement part. I had to buy a set of metric Allen wrenches to disassemble the pump but it wasn't too hard.
You may have an altogether different problem and give the cost of a new pressure washer it may just be time to upgrade. Hope this helps.