I have repaired several of those almost every one of them would not build pressure due to the the 3 plungers each one has a small screen a small spring and a small rubber disk need to take them out and clean and inspect there is a repair kit they sale for that power washer that gives you every thing I describe but they are more than likely clogged up be careful taking it apart the parts are very small well lighted room clean floor just in case you drop something