Re: power washer
You might want to check out your unloader valve!
What this valve does is relieves the pump. When you release the trigger on the wand the water has no where to go and pressure builds up. The pump will not continue pumping when there is no water that needs pumped, so the engine will not be able to turn the pump and the engine will shut off.
So basically, the unloader valves job is to relieve the pump of the excess pressure until you pull the trigger again, if the valve is stuck, the pressure will not be relieved and the pressure washer may not star back up after shutting off.
Check this out, and if it works let us know, if not, hopefully someone else has some ideas!