Electric Karcher pressure washer surging when turned on

Dear firenutt681,
One simple thing you can do, is to check for leaks. Check if hose at machine is leaking. Check gun if it is leaking. You can also check if water still comes out of lance nozzel. These leaks however so small, will cause the machine to surge.
Another reason is due to a faulty SPILL VALVE. This spill valve( often called CONTROL VALVE) will contract when the gun is closed. When it contracts under the enclosed pressure it will switch off the machine by means of a Micro Switch. Now if this Spill valve is faulty it will loose its compression under pressure and puts on the micro switch again. This can be seen once in a while or more frequent, as in your case. I sometimes do service Spill Valves, but mostly I replace them with a new one. I do not know the model number of your machine, but normally you have to open the cover and you should spot the spill valve on the head. Most probably you see a thick wire or a cap containing the micro swith. If you find the micro switch, you have found the spill valve. Sometimes it is a bit hard to pull out the spill valve. Myself, in various Karcher models I remove the spill valve by trying to feed water and put on a bit the machine. In this way the spill valve will be spitted out.
Another reason which makes your machine surge, is leakage from from the detergent inlet.
If you do not see no leakages at all....then for sure it is the SPILL VALVE.
If you cannot do this job yourself or you do not find spare parts...you can continue using the machine as it is...but before closing the gun...switch off the electricity. I only recommend this in an emergency. You do this so that you do not leave the machine surging. This surge will for sure damage the electric motor and the capacitor (assuming it is single phase).
Regards,
Fulltech.

I have had the same problem. It is the o-ring on the plastic check valve, located on the inside of unit and accessed when you remove the metal clip holding the water inlet piece. You cant buy a new check valve by itself, or the oring from a Karcher parts supplier. But you can get a new mm size o-ring from the online O-ring store. Just not sure what exact size. Possible 1.3 to 1.5 cs and 3 to 3.5 ID. If you locate the correct size, let me know!