pressure washer pulsating

backdraft341May 4, 2007

i have a landa pressure washer that sat up for years. i got it out and it started fine and pumped good. then i decided to change the pump oil. now the pump pulsates. i can figure out why. any ideas?

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i am not sure about a landa. But a Karcher will pulsate if it has a blockage or the throttle is too high. What happens is the internal pressure builds up and trips the bypass valve, once the pressure is relived it starts the cycle over.

    Bookmark   May 4, 2007 at 10:12PM
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broke_not(3 ND)

Does the pump have hex-head caps over the tops of each piston bore? If it does, remove the caps and carefully pull out the spring-loaded one-way valves situated just beneath the caps.

The one-way valves will be seated against the pump body with an o-ring, but will come right out. Once they're out look at each one and compare them. Inside the plastic cage there'll be a light spring that holds a dish-shaped metal valve closed against the bottom side of the valve. You'll likely find a small piece of grit or rust holding one or more of the valves off of its seat.

Here's a breakdown of a cheap pump.....yours won't be like this one if it's a Landa, but the one-way valves should look the same. They're reference number 3 in this drawing:

    Bookmark   May 6, 2007 at 10:14AM
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broke_not(3 ND)

I should have also mentioned that when you have the caps off and the check valves out, look inside the pump where the valves sit and make sure you have all of the o-rings and such accounted for. Then, attach your garden hose to the pump and turn the water on without running the motor/engine that drives the pump.

Just let the water run for a minute or so to flush out any remaining debris so when you button everything back up one of the valves doesn't get stuck again right away....

    Bookmark   May 6, 2007 at 10:20AM
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indy452(NC Kansas)

Did you use 30W non detergent oil? Ive changed oil in pressure washers pumps and it says to use non detergent oil. I have no idea if that would affect the pumping action but I thought I'd throw that out.


    Bookmark   May 6, 2007 at 11:50PM
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How fast is it pulsating? If it is rapid, once per revolution, you should look at valves and high pressure seals, as one cylinder is not pumping right. If it is much slower than that, you probably have an unloader or plugged nozzle issue.

    Bookmark   May 7, 2007 at 9:59AM
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i have a double wand. the top one is for appling agent. if i open the top one a little bit it stops pulsating. when i close it of and go to full pressure it starts agian. the wand has a handle you twist on for agent and off for pressure.

    Bookmark   May 7, 2007 at 1:37PM
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Again, how fast does it pulsate?

    Bookmark   May 7, 2007 at 9:49PM
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I have a new yellowstone high pressure washer and it has begun to pulsate slowly. At first it was working perfectly. After 20 minutes of use, it began to exhibit slow pulsating streams about 2 seconds apart.

I looked at the filter that leads to the water supply hose. Nothing was blocking the filter.

Anyone have any ideas as to how to correct this?

Thank you,

    Bookmark   January 23, 2011 at 7:20PM
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