You can check the pump packings, usually they worn out with usage, not letting the pressure washer hold pressure. If that doesnt solve the problem I'd recommend check the unloader after. The unloader is that part by the pump that you twist in order to regulate pressure (even though i wouldnt recommend anyone doing so, since you can regulate pressure by engine rotation).In order to do that, you would have to disconnect the unloader, connect the quick connector from the unloader back on the machine, and run the machine. When you do that ALWAYS have the trigger pressed on the gun and DO NOT let go, if you do not do so, there is a huge chance you might damage your pump. If the machine runs fine without the unloader, then you found the problem. If not then it should be the packings.