K5.85 model Karcher washer stopped pumping and only humming.

Yes, the on off switch is probably bad, go to karcher.com for parts and schematics.

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.

Dear Sir,
I came across a lot like this problem as an expierienced technician on power washers.
Most probably there is a capacitor, which when faulty, it gives this condition.
If you know with all respect to remove the pump from the electric motor, try starting without load.
It is possible that the problem is in the pump. If the electric motor finds that it cannot turn because the pump or pump pistons are jammed...it will hum and stops. I hope you did not do this very often...because you may have damaged the electric motor for good. Also important never put on a power washer without water supply. To test you can feed water but remove the gun...so that there is no load. Hope it is the capacitor in your case. Now the capacitor gets faulty from another fault. One of them is that when you were using the machine and closed the gun, the power washer stayed getting on and off all the time. This will damage the capacitor for sure. If you make a new capacitor ad machine starts and stops when gun closed....there is problem with control valve (Spill Valve). Hopefully the valves are OK. The spill valve you will locate inside...generally always you see wires coming out of it. Spill Valves are rarely serviced...myself I change with a new one. This what I am explaining is for nearly all models.....but I do not know your type of model....so I appologize if I am not explaining for your model. Well if you know how to open the cover...you can pin point what I said. Many Karcher covers are opened with screw drivers Torx T15.

sounds like the seals & o'rings are faulty.get the model number of pump and purchase a kit for the pump.replace all seals and o' rings.this will stop the oil from the pump going through the nozzle.

Don't know this model intimately but it looks similar to the Karcher which is really total **** nowadays as its all made of plastic. The motor has a weird switch mechanism but if it tries to run and the motor doesn't then 100:1 the motor is seized. Very unlikely it's the actual motor but the pump is a "swash" plate that opens 3 stainless steel thin flat valves. the bearing that the pump shaft goes through is a phospher-bronze plain bush with a seal each side and if this has dried out then you are screwed. Same if you model has steel roller bearings. However, if it does run and build up pressure and it stops because the output pressure is too high then the overload pressure switch is faulty. If it is the Karcher type then again you are stuffed but if it is similar to the Nilfisk then a replacement is available for around £100 GB Pounds - probably cheaper to buy a new one.

the motor has sized up on you free it off if you can giveing it a splosh of wd40 in the bearings may help

Dear K_mccurdy,
I am assuming that your washer is single phase. A comon reason for humming is a faulty capacitor. This must be changed by a new one.
Now one must see why the capacitor got damaged. This could happen, when the gun is closed the machine starts and goes off again in short intervals. In this case a control valve, often called the Spill Valve, needs lubrication or replacement. I prefer to replace it. Even if the pump has no faults and you have a habbit of closing and opening the gun more than necessary...the capacitor will get damaged. It is also important that if you use soap or chemicals, always rinse with fresh water before storing away the washer. Also never store the washer with pressure still built up. Always release the gun, before storing. Well in your case it must be the capacitor. If the capacitor is OK or you have changed it....try the washer without load. This can be done by removing the gun. You can leave the water supply, for this has a cooling effect during this test. Things should work fine now. If not...then the electric motor must be checked. But I repeat...the most common fault for humming is a faulty capacitor.
Regards,
Fulltech.

The machine has a pressure leak. Check for a cracked controll head or either a leaking outlet elbow. The machine will short cycle if the holding pressure can not be maintained

Hi the pump surges when there is a leak on it find the leak that should sort your prob.
Hope this helps. Sean