Finally a subject in my area of expertise. A hot water pressure washer is the best way to clean grease/oil off motors, frames, garage floors ect. I've been selling them for 25 years. They are not always the easiest things to repair if you don't understand how they work. Now I'm sure your thinking its just a pump, heard that alot over the years from experienced truck and heavey epuipment mechanics, but they always seem to call me after they have given up trying to fix it themselves and often times it is not even a pump problem.
If you can buy it cheap, go for it and I can help you trouble shoot it. JUst don't tear into it first without contacting me, I can probably save you time and money. Just like any repair job, there is a proper trouble shooting order to follow.