Karcher 520M wont operate at high pressure

Question edited for clarity.

The Gun has what it calls a 'Pressure Spring'. See if it is broken. The system is different to my Coleman pressure washer which has a switch that senses the water pressure has dropped when the trigger is pressed and turns the motor on.

Click the link that says 'Show More Parts Diagrams'.

https://www.ransomspares.co.uk/parts/brands/karcher/pressure-washer-spares/k5%20compact%20eu%20(1.630-720.0)/

Troubleshooting

Karcher Outlet
https://www.karcheroutlet.co.uk > Troubleshooting
If the machine is pulsing whilst in use, it may be that the accessory you are using has a blockage. Clear by soaking the accessory in warm soapy water and then ...

Troubleshooting Electric Pressure Washer

K?rcher
https://www.kaercher.com > services > product-support
Machine not turning on · Machine "hunting" or "pulsating" · Water leakage · Accessory not fitting into trigger gun · High pressure hose will not stay connected. ..

Have you tried servicing the motor. Fresh air filter, new fuel filter and a fresh spark plug? That will help narrow down what the problem could be.

Your unloader or your packing could be cooked and these washers can be a pain to work on or to even find someone to work on them. Since it is a cheaper fix I would replace the adjustable nozzle on your wand first. Those are notorious for going bad. Then you have no pressure and you think your pump is bad. Most electric washers arent worth working on as the cost of parts and labor often exceed the cost of buying a new one. look on your manual for the unloader and packing or jsut go here. FIND PARTS FAST Good luck!

try turning the motor by hand somehow to c if u can free it then try again or possible bad capacitor??

If the pressure unloader is not working correctly and/or the nozzle is partially clogged with debris, the engine will be overtasked. Try lowering the pressure by turning the pressure knob to lowest setting and test. If the engine continues to run, gradually increase the pressure. Try using the washer set to about 75% of rated capacity and use max pressure for stubborn stains. Using any machine at max will shorten the life of components. If lowering pressure does not help, then unloader is faulty or stuck. Try storing the unit with oil in the pump. Remove both hoses and infuse oil into water inlet intill all the water is displaced (let set for day or two). Good luck

Yes, the water should be turned on first but if it only ran for a minute or two it should be OK. Most late model pressure washers have an automatic shutoff when the trigger on the wand is released. Turn on the water and then the machine and then squeeze the trigger on the handle of the wand and the motor should start as soon as the air is cleared from the line by the flowing water (about 10 seconds). If the unit was put away wet last season you may need to clean the nozzle with a piece of wire too.

This may not be a motor problem. It sounds like your pump is not working properly and the motor is just following the pump. First thing to do is check for leaks in the pump, wand hose, gun etc. It may also be a blown water seal inside the pump.

replacing the wand wont solve the pressure problems, its going to be the pump problems, pump create high pressure to the wand. hope that help

The wands that it will not run with would most likley have a little dirt in the tip of the nozzle. This would not allow the water to flow through in turn activating the pressure switch and shutting the machine down

Troy

I had the same problem - good water inlet pressure, no output pressure, even though the lance and handle seemed to be clear and working find.
I found that the electrical switch wasn't being operated correctly by the spill valve and wasn't turning the motor on/off correctly.
Inside the plastic electrical box there is a small white device that presses against the micro switch assembly. Carefully adjust the allen screw perhaps 1/4 turn out or 1/4 turn in to obtain correct operation of the microswitch - you will hear the micro switch clicking in and out when re-assembled. I'm sure they must have a rig to check correct positioning of this screw in the factory!
Hope it helps - mine is working find now and saved me buying another!