I have a Generac pressure washer, about 2700 psi. Last summer lost all pressure. About same time engine began surging (up and down rpm's) while idiling. Replaced unloader valve and still no pressure. Later, in fall, still surging at times and even not running, at times, without choke being part way on.
Recently I took apart and cleaned the carburetor. It looked pretty clean when I got in there, but I think it helped. Now runs with very little surge and without choke applied. It even produced pressure for a few seconds before it ran out of gas, but now no pressure again!
When engine is running and there is no pressure I hear some rattling in area of the pump.

If anyone has any ideas, please help!

Thank you Administrator for replying, but I'm ok now.
I took the pump off of the engine shaft and was able to spin the pump "shaft" freely....no grinding or noise. I also took the unloader valve out of its seat, but I doubt this affected anything since the unloader valve is new. Also, there's a very narrow, inch long piece of metal that fits into a groove on the engine shaft where the pump slides over it. That fell out and I slid it back in.

When I put it back together it worked! I used it for over 30 minutes.
Feel free to let me know if you have any idea what the problem could have been.

I gained some good experience along the way for future repair work!

Hey, thanks for the key info. Hope you had a good New Year holiday.
Maybe talk to you on my next forum question.

It sounds like you've been through quite a journey with your Generac pressure washer. Dealing with pressure loss and engine surges can be frustrating. Kudos for your troubleshooting efforts so far, like replacing the unloader valve and cleaning the carburetor.
Since you mentioned hearing some rattling around the pump area when the engine is running but there's no pressure, it might be worth checking for any loose components or debris around the pump. Also, make sure all connections and hoses are properly secured.
Considering you saw some improvement after cleaning the carburetor, there's a possibility that there might be some fuel delivery issues affecting both the engine and the pressure generation. Double-check the fuel lines, filters, and ensure proper fuel flow to the engine.