Pressure washer keeps buzzing loud?

It is bwoken you wascally rabbit.  Take to a shop and have them fix it or you will burn out the motor.

Make sure it isn't clogged because it will crack the housing if you keep running it 

read manual under troubleshooting.  had one that wouldn't work -- turned out the nozzle was clogged -- removed and cleaned -- worked fine.  other possible problems -- motor won't start due to capacitor needs replacing -- inlet or outlet clogged elsewhere -- pump has died ..

Replace capacitor.