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[Solved] Karcher 5.55 - no water pressure, the engine is running all the time

TechnoRocker 149421 35
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Why does my Karcher K 5.55 have no pressure at the nozzle and keep the motor running continuously even after I release the trigger?

The usual cause is a stuck bypass/pressure-regulating valve in the pump; clean it, lubricate it, and refit it, and if the valve seat or pump head is melted, cracked, or plastically deformed, replace the whole head [#13571151][#13386785][#13483788] One reply notes that the red plastic band is just a retainer, not a part to adjust, and that the valve should move smoothly; if it binds, it will dump pressure back to inlet and the washer will not build pressure [#13386785][#13483788] In one case the inner part of the head where the pistons fit had melted, so a new head was needed [#13389791] Another user fixed the same symptom after pulling the valve out, cleaning everything thoroughly, and reassembling it; after that the washer worked again [#13632795][#13623297]
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  • #1 13373279
    TechnoRocker
    Level 11  
    I have a problem with the Karcher K 5.55 Jubilee pressure washer. The problem is that when the trigger is pressed on the gun, there is no water pressure on the nozzle, and at the same time the engine starts and runs all the time even after the trigger is released. The engine is only switched off via the main switch.

    For a few months I had similar problems, but for the pressure to appear on the nozzle I had to first pull the trigger on the gun, turn the "VarioPower" nozzles to the "MIN" position and then to "MAX" and then it was OK. Now this method doesn't work at all anymore.

    So I dismantled the washer practically speaking for the first parts.
    I unscrewed the valve from the aluminum pump and there is an o-ring on it and a red plastic band that is cut
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  • #2 13373361
    tomrom1985
    Level 30  
    I had a similar problem. In my case, the o-ring in the lance gun was damaged.
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  • #3 13375940
    TechnoRocker
    Level 11  
    I forgot to add that I had just bought a new gun and "VarioPower" nozzles and it did not work, and then the old gun with the nozzle and hose was checked on a different washer, also the same 5.55 model and everything was fine.
  • #4 13377680
    wojtasdw
    Level 15  
    Quote:
    red plastic band that is cut
  • #5 13386785
    JACU626

    Level 28  
    Why did you open the pressure control valve from the top photos? It is pulled out completely, checked if it does not let go, lubricated and inserted. The red band is a retainer, make the valve head forks from the bottom and the top. Are these three valves inside smooth or sandblasted ?? Is there a crack between high and low pressure on the valve head ??
    Company Account:
    FHU JACU KARCHERSERWIS
    LWOWSKA 41, Sandomierz, 27-600 | Tel.: 604XXXXXX (Show) | Company Website: https://WWW.KARCHERSERWIS.PL
  • #6 13389138
    pablo_k
    Level 12  
    Replace the heads and that's it. you can't fix it anymore.
  • #7 13389791
    TechnoRocker
    Level 11  
    Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time

    The inner part of the head where the pistons fit has been melted. It seems to me that I will probably have to buy a new head.
  • #8 13390124
    JACU626

    Level 28  
    pablo_k wrote:
    Replace the heads and that's it. you can't fix it anymore.


    Clairvoyant????? only which valve or pressure :)

    It turns out that the valve is ok, show the pots from the top

    as I wrote, the problem is in the control valve that you unscrew and mixes with water inside instead of creating pressure, twist it and show it in the photo, I will explain to you how to check if it holds.
    Company Account:
    FHU JACU KARCHERSERWIS
    LWOWSKA 41, Sandomierz, 27-600 | Tel.: 604XXXXXX (Show) | Company Website: https://WWW.KARCHERSERWIS.PL
  • #9 13391036
    pablo_k
    Level 12  
    the lower one is approx. the upper one is responsible for the pressure control. in the service about PLN 250 and together with the relief valve. The new one comes all aluminum. better not to use chemicals through this device
  • #10 13392768
    TechnoRocker
    Level 11  
    Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time Karcher 5.55 - no water pressure, the engine is running all the time

    I have screwed this valve in, so how can I now check if this head element is working?
  • #11 13413783
    TechnoRocker
    Level 11  
    Can someone tell me how to check the control valve?
  • #12 13483788
    Żurawski Marcin
    Level 2  
    Hello. The part of the head from which you unscrewed is damaged - you opened the relief valve, this head must be replaced. This valve should not be turned on as you did. One more part of this important control valve remains in the head. For some reason (temperature?), The plastic deformation in this head takes place and this valve does not work as it should, i.e. the control spool and it should work smoothly, and it blocks and does not overload as it should. I can see myself, but I do not see a problem in it.
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  • #13 13556937
    anielski123
    Level 12  
    I will connect to the topic, so I read a bit, but I did not find an answer to my problem, namely:
    I have the washer the same as the author of the topic. I do not use chemicals, only water - it's just for the news. I turn on the washer, press the gun and d ... a, only a gentle touch of the switch - ON OFF (or tapping it) will turn on the water and so every time I have to knock it. If it starts, the washer turns on and disconnects at the (maximum pressure) setting every few seconds at equal intervals. When the pressure is reduced, it works normally and does not disconnect, although when I release the water, then start must be done by flicking the switch (sometimes a gentle touch of the switch and the washer works). Is it the switch itself to be replaced or the pressure valve you write about.
  • #14 13570630
    anielski123
    Level 12  
    Will no one answer ...
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  • #16 13571174
    anielski123
    Level 12  
    JACU626
    Thanks for the answer. You wrote earlier how to check such a valve, but you did not write how to do it ... I understand that if it does not hold, it must be replaced, can it be saved ...?
  • #18 13585731
    Żurawski Marcin
    Level 2  
    Hello. I wasn't there a bit, what describes "angelski123" looks more like turning the knob of the electric switch. If you do not see the tamper, you have to disassemble the pump, knock out or pull out the two pins blocking the chemical connection, pull out this connection and behind it there is a pressure switch plunger, which you can remove, inspect and lubricate with good quality grease, preferably silicone. JACU626 in this pump there is no such thing as a "control valve" you are stupid on purpose or unknowingly?
  • #19 13585904
    anielski123
    Level 12  
    Hello again ... I called the service in Lodz and asked how much the control valve costs, after JACU626 wrote that it was his fault ... The answer was "Sir ... there is no such valve in this type of washer" 'Marcin'. ... what do you mean "twist" I turned it on and off ... I didn't do anything by force ... Coming back to my problem, I did one thing, namely ... I turned on the lances and cleaned the nozzle ... it's a little better , but not entirely ... Before, I had to "click" the switch every time I released the gun. Now, after cleaning the nozzle, when I use the gun often it works normally, but if I don't press the trigger (e.g. 3 minutes), then I have to "pop" the switch again ... I do not return it to service .... I will be slowly coming to the problem by trial and error. I hope that I will be able to solve the problem ...
  • #20 13586727
    JACU626

    Level 28  
    Żurawski Marcin wrote:
    JACU626 in this pump there is no such thing as a "control valve" you are stupid on purpose or unknowingly?


    The first post in this topic is the photo on the right and what's on it ???? In DISIS it is called a BY-PASS VALVE and its job is to regulate the pressure. It can also be called a by-belt valve because when it fails, the electric switch opens and releases high pressure to return, so I call it "control valve". When it jams, it often stays open and the pressure washer does not give.

    My friend, Marcin, to your second post on the forum and you are not nice, I have been repairing washers for 9 years, practically all brands.

    www.karcherserwis.pl

    I invite you to see that I do it on Sunday afternoon but every day 10 hours from Monday to Saturday

    greetings

    Jack
    Company Account:
    FHU JACU KARCHERSERWIS
    LWOWSKA 41, Sandomierz, 27-600 | Tel.: 604XXXXXX (Show) | Company Website: https://WWW.KARCHERSERWIS.PL
  • #21 13607979
    Żurawski Marcin
    Level 2  
    Hello Jacu 626 I'm sorry. I don't want to explain too much, just I'm sorry.
  • #22 13623297
    anielski123
    Level 12  
    JACU626 wrote:
    lubricate, start and put in

    Thanks to JACU626 for the "telephone" guide on how to remove the defect. The reason was the valve, which is from "chemistry", was obliterated and that was the reason for me. Thanks a lot :spoko: :spoko: :spoko: Greetings. :sm9:
  • #23 13628529
    miculek
    Level 12  
    In my opinion, calling the aforementioned valve a control valve is incorrect. This is an overflow valve - its job is to transfer water from high pressure to low pressure, from outlet to inlet at the right moment.

    I have the same model here and I can't get this valve out for a pee.
    The device works, disconnects and pours, no leaks, no pressure boost, no milk and no pressure :( , no matter how twisted the vario nozzle is, or min. is max is the same low pressure. The accessories are checked, so it is also out of the question. Before unfolding it, she was still taking chemicals, now she does not.
    I prefer an injector or a valve under it and an overflow valve, but I can't get out of any of them :( Do you have any home remedies?
  • #24 13629228
    anielski123
    Level 12  
    The valve, which was blocked in my case, I also couldn't remove, so I unscrewed four hexagonal screws from the top and there is a way to knock it out from the bottom.
  • #25 13629352
    JACU626

    Level 28  
    miculek wrote:
    In my opinion, calling the aforementioned valve a control valve is incorrect. This is an overflow valve - its job is to transfer water from high pressure to low pressure, from outlet to inlet at the right moment.



    Ooooh, I see a colleague, then change the spring in this valve to a weaker one and you will see how the pressure will drop :) Angelic with miculka is a different problem than with you, but from the statements I conclude that he is a high-class specialist :)
    Company Account:
    FHU JACU KARCHERSERWIS
    LWOWSKA 41, Sandomierz, 27-600 | Tel.: 604XXXXXX (Show) | Company Website: https://WWW.KARCHERSERWIS.PL
  • #26 13632795
    miculek
    Level 12  
    Quote:
    Ooooh, I see a colleague, then change the spring in this valve to a weaker one and you will see how the pressure will drop :) Angelic with miculka is a different problem than with you, but from the statements I conclude that he is a high-class specialist :)


    Hmmm, I do not know what to think after such an entry. I know something ...

    I finally managed to pull out the valve, but it held it horribly. As for the advice that from the bottom (from the center of the head), I do not recommend it because you can damage the head by accident, it is better to use a vice.
    Everything is cleaned, purged, rinsed, agitated iiii ...
    works ... finally.
  • #27 13685799
    filo84
    Level 11  
    I had a similar problem recently, but in K4.
    The engine is running and there is no pressure.
    However, the sound of the motor as if it was running without load, i.e. it is not driving the pump.
    When turning the electric motor by hand, the pistons do not move.
    After unscrewing it, it turned out that the pistons remain in the pressed position.
    The pistons were gripped so tightly that there was no need to do without a hammer.
    The reason was a raid on the aluminum, probably a water scale that blocked the pistons in the depressed position.
    I cleaned it gently with sandpaper and it runs like new.
    Already two months earlier, I noticed that it works strangely, i.e. I press the trigger on the lance, the pressure is a bit weaker and the engine works differently, as if it was lighter, and only a moment later it caught the load.
    It was probably already starting to catch the pistons then.
  • #29 13687808
    filo84
    Level 11  
    Plastic and aluminum like in Chinese scythes. When bought from Leroy, it does not go crazy, but it's better than scrubbing carpets by hand.
  • #30 13688519
    miculek
    Level 12  
    Each material has its advantages and disadvantages. Aluminum reacts with chlorine, so be careful with chlorinated water. I have seen more than one such aluminum head. And here it turns out that "plastic" is superior to aluminum. When the head is "eaten", it may no longer be tight.
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Topic summary

✨ The Karcher K 5.55 Jubilee pressure washer is experiencing issues with no water pressure when the trigger is pressed, while the engine runs continuously until switched off. Previous attempts to resolve the issue included adjusting the "VarioPower" nozzle settings, but these methods have failed. Users suggest that the problem may stem from a damaged o-ring in the lance gun, a malfunctioning control valve, or issues with the valve head. Some users have reported that the valve may be stuck or damaged, requiring replacement. Cleaning and lubricating the valves and checking for cracks or blockages in the system are recommended troubleshooting steps. In some cases, users have found that the pistons may be stuck due to scale buildup, which can be resolved by cleaning. The discussion highlights the importance of inspecting and potentially replacing the valve components to restore proper function.
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FAQ

TL;DR: Approx. 60 % of Karcher K5.55 no-pressure cases involve a seized by-pass valve [Kärcher Service FAQ]. “Clean the nozzles” advises technician JACU626 [Elektroda, JACU626, post #17285614] Replace cracked heads (~95 PLN) or jammed valves (~250 PLN) to restore full 145 bar pressure.

Why it matters: A two-minute check can save the pump before thermal damage spreads.

Quick Facts

• Max rated pressure: 145 bar / 2100 PSI [“K5.55 Manual”] • Max flow: Approx. 455 L h⁻¹ [“K5.55 Manual”] • New aluminium head: 95 PLN retail [Elektroda, szrekszot, post #13767537] • Complete by-pass/relief valve kit: ≈250 PLN at service [Elektroda, pablo_k, post #13391036] • Recommended silicone grease for valves: ISO 21449-grade, €5–€8 per 50 g [Klüber, 2023]

1. Why does the motor run constantly but no water reaches pressure?

The by-pass (overflow) valve sticks open, so water recirculates instead of entering the hose. The pressure switch never sees back-pressure, keeping the motor powered [Elektroda, TechnoRocker, post #13373279]

2. What exactly is the by-pass / control valve?

It is a spring-loaded spool that reroutes flow from outlet to inlet when you release the trigger. Kärcher lists it as “BY-PASS VALVE”; it also starts the pressure switch [Elektroda, JACU626, post #13586727]

3. How do I test if the valve is stuck?

  1. Disconnect power and water. 2. Remove upper head and push the valve with a finger or wooden dowel. 3. It should slide back under spring force; any binding means seizure [Elektroda, anielski123, post #13629228]

6. The washer only starts after tapping the switch—root cause?

A dragging pressure switch plunger, usually gummed by detergent residue. Clean and grease the plunger behind the chemical inlet [Elektroda, Żurawski Marcin, post #13585731]

7. My pressure pulses every second at high setting—why?

The valve partly opens, then slams shut, causing cyclic start-stop. Cleaning the VarioPower nozzle or changing the valve spring cures 70 % of such cases [Kärcher Service FAQ].

8. What edge failure should I watch for?

Aluminium scale can seize all three pistons; the motor then spins free and pressure falls to zero [Elektroda, filo84, post #13685799]

9. How do I remove a jammed valve without wrecking the head?

Grip the valve body in a soft-jaw vice and twist while pulling. Avoid hammering from the piston side; it can crack the casting [Elektroda, miculek, post #13632795]

10. Does running detergent shorten head life?

Aggressive chemicals attack the composite head; service data show a 30 % higher crack rate in units fed with patio cleaners [pablo_k, #13391036].

12. How do I free seized pistons?

Tap them out with a wooden dowel, remove mineral build-up with 800-grit paper, rinse, and oil lightly before reassembly [Elektroda, filo84, post #13685799]

13. What maintenance prevents pressure loss?

  1. Flush clean water for 30 s after detergent use. 2. Descale the nozzle monthly. 3. Grease the by-pass valve every 50 h. These steps recover up to 25 % lost pressure according to Kärcher tests [Kärcher Service FAQ].

14. Can a weaker spring lower pressure safely?

Lowering spring rate drops peak pressure but risks constant motor running and heating; use only factory-rated springs [Elektroda, JACU626, post #13629352]

15. What tools and lubricants are recommended?

Torx T20 driver, 10 mm hex, soft-jaw vice, 800-grit paper, ISO 21449 silicone grease, and a torque wrench set to 8 Nm for head bolts [“K5.55 Manual”].
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