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Karcher 551c pressure washer problem.

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Hello all


At work we have the above pressure washer that’s not worked since I started there. My task is to try and repair it. When I first plugged it all in, water was leaking out the side of the motor and the oil was milky. I’ve taken it apart, replaced the oil and pressure seals and now there’s no leaks but it doesn’t start up. When you’ve plugged it in and then pull the trigger it makes the noise as if it’s going to work but then it’s stops and makes no effort to start again.


Can anyone think what to check next?





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Electric or Petrol? If electric - the motor usually starts up when you release the mains water pressure by pulling the lance trigger, a plunger mechanism registers the drop, a switch kicks in and the motor turns on. If the motor isn't switching, it is probably the switch or possibly the plunger that registers the drop in water pressure is stuck.

Not done petrol ones but am guessing they work in a similar way.

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Hello bud


Its an electric one but it also runs on diesel for heat. It’s not been started for a few years so maybe the plunger is stuck! Water is getting to the handle on the lance because it was dripping from there. When you pull the trigger it makes the sound of starting and the lance kicks a little as if there’s pressure, but then nothing.  Where roughly would the plunger be?

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Hi spud

Sorted the pressure washer Found the plunger you talked about, took it apart, cleaned it and then had another go and the washer made some new noises which sounded good. I then noticed the fan move but then stop and become solid, so I stripped the lance and the pressure nozzle had become blocked too, cleaned that out and hey presto

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