Question about Karcher 1750 psi Electric Pressure Washer

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Motor/pump pulses--like a rapid on/off rather than a steady hum

The last time I used my sprayer, it wouldn't spray at all, and the user manual led me to believe that there was air in the pump. I followed manufacturer's instructions, and now it's spraying. But, the motor and/or pump seems to be malfunctioning when the sprayer arm is not activated. It's a "rum - rum - rum" pulsing sound with "beats" about a second apart, rather than a steady hum of a motor. It draws down the electricity in my garage with each pulse--the lights dim. When I'm actually spraying, the motor seems to level out--and the lights are okay. I'll appreciate your advice. I'm a widow, and I can't afford to call a repairman every time I would have ordinarily turned to my dear husband. Thanks.


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  • patrickferg Nov 05, 2008

    I have a 3 year old, lightly used KB9030 doing this pulse trick. It's ok when spraying, though I think pressure is a bit less than it used to be. In addition, after about 10-15 minutes minutes use the motor cuts out completely, and won't start for about 15 minutes. Now I'm a reasonably skilled DIY-er, and have stripped the machine down several times to investigate, but with no luck. One suggestion from the web was that it was the control head, which I've dismantled,examined and result.! Also, I've tried changing the inlet pressure. Do I look for a new one?

    Thanks, Ferg

  • lou20227 Nov 12, 2008

    Same problem as above,spray ok no external leakage,motor is 100%,I replaced,cylinder head k 200,valve cage and spring, its still doing the same problem.I electrician/Refrigeration Mechanic by trade,and spill valve where about is that the valve cage or something else,and i got the manuel right in front me i couldn`t see the name of spill valve.believe me not even a spit of water dry as a bone easy to know that is loosing pressure the suction chemical valve keep going in and out.because is the on that when it fill with pressure it goes off and you hit the rigger it release and switch back on.

    thanks a lot


  • Anonymous Apr 22, 2009

    Hi "Its alive",

    It looks like that you know what you are talking about, but I cannot figure it out:
    What is the "control head"? HP side I assume stands for high pressure?

    I removed the yellow cover, and the rho pipes. I found a small metal thing with a red plastic attached. The red plastic has four holes on it... looks like some kind of filter... I tried cleaning it out, it didn't help

  • Anonymous May 12, 2009

    intermediate pumping and low pressure



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I had the same problem,and I replace the spare part set control head parts,Same problem when it goes hum hum,if you look inside it with a magnified glass you`ll be able to see hair crack line.

Posted on Mar 17, 2009

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Replace the control head. Water leaks from the HP side,through the o-ring on the piston to LP side. This then triggers the machine to start since it's lost the 120bar pressure which is required to keep the machine off. If you can source the correct size of o-ring just change it out. If not use E-spares for the part which costs £12

Posted on Mar 16, 2009

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Good morning to all
I am an Italian and working in a repair Karcher. After reading your post I can say with certainty that your problem is the breaking of a component of the pump called collector. The breaking of this component leads to a continuing power of the machine for 10 minutes and the loss of pressure during the operation. To repair should consult your local Karcher.

Posted on Dec 07, 2008

  • CanAmSteve Jun 11, 2011

    I suppose it is to Karcher's benefit that repairs require a Karcher repair shop to complete them?

    Be careful of freezing, the design of these machines is poor and any residual water inside will freeze and break components. In Italy it obviously never gets cold, but if you live anywhere it freezes, take the machine inside for the winter, I guess, Yes, inconvenient and messy, but parts are expensive!


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Dear Brainpicker,
I think..(with all respect)...that the last time you used your sprayer, you swwitched it off and left it with pressure in the system. When one finishes using such machines, it is important that the pressure is released by pressing the gun. If these machines are stored with pressure still in the system, damage will be done to various parts, especially the spill valve. This is also more importantant for SAFETY reasons. The fault you have is most probably from the spill valve. In this case it should be changed with a new one. This job can only be carried out by a specialised technician. I wish to add, that this problem could also be caused by leakage. Check if the gun is leaking when it is closed. Also check if you see any water under the machine. This means the head is leaking. Very sorry but this problem requires a qualified technician or a person with expirience.

Posted on Nov 05, 2008

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