Motor does not shut off when trigger on wand is released

If you are unable to shut off the pressure from the wand, there may be an issue with the unloader valve that is stopping it from switching into bypass mode when the trigger wand is released. The unloader valve is designed to respond to the spike in pressure created when the trigger wand is released, and to divert the flow of water coming from the pump to bypass the pressure hose and flow back into the intake end of the pump. If the unloader valve fails to switch into bypass mode, water may continue to flow out of the trigger wand. This may also cause damage to the wand. If you are unable to shut off the pressure from your power washer, stop the engine and discontinue use immediately. The unloader valve should be removed and possibly replaced if found to be malfunctioning. The inability to stop the flow of high-pressure water from the wand can be dangerous and should be fixed before continuing to use the machine.

I think you have one of two things going on hear, an overpressure problem or a carburetor issue with the engine.

Your pressure washer is either not fitted with a run/stop device in which case like mine you have to switch off within a few seconds of closing the trigger. Check your model features?
The humming noise is the motor stalled out against the pump because there is nowhere for the water to go. The shutoff is caused by the safety overload switching off after overheat.
Or, it has a pressure operated run/stop which is not working. Because water and electricity don't mix, I would suggest getting more specific help. You can download Karcher manuals /spares lists online from Karcher specialists but remember electricity is the silent killer.

it sounds like a flow switch that is installed in the inlet of pump can get stuck at times if you have a soap nozzle select it usually more flow moves the flow switch try and clean the flow switch if possible.

any leaks from connection at pump to gun and wand assembly if so the valve is detecting leakage and open up again without u squeezing trigger it builds up in the head.if your trigger gun is leaking internally then you will need to replace the gun this unit uses a trap pressure unloader valve

Pressure washer when you first try to start them that stop underload. We had the same type of problem with 11 hp Honda if you hold the trigger open the motor will be under less load we found by running the motor for about a minute it would work normally. Remember to make sure the water hose is turned on pull the trigger on, until water is coming out of the wand , now try and start the motor but also hold the trigger open, now you will not be building maximum pressure, after about a minute release the trigger and see if it keeps running.

spill valve is stuck and needs to be cleaned and greased common problem....also check all connections for blockage in line

hi,
there is a small ball bearing inside the nozzle on the end of the lance , this can get jammed or missaligned and the nozzle orifice can get blocked , clean this or replace the whole lance with another 200 Bar lance .

hope this helps

it is normal,It is the governor on the engine that does this.

common for not starting unless trigger engaged as you are turning the pump as well as engine creating pressure,as for stalling pump has unloader valve which is probably in need of grease(use good silicone grease)this allows water to ciculate when trigger released.