Pressure washer woes

My nearly-new Kaercher pressure washer has developed a problem... when I use it with the 'normal' wand (as opposed to the twirly dirt-blaster thingy), the motor/pump keeps cutting in and out so that I get a pulsatile flow of about two blasts per second. (I have occasionally seen this with the twirly wand as well).
What could be causing this? I wondered about a partial blockage in the wand - would that cause these symptoms? It seems to work perfectly well when the pump is in its 'on' phase, and I can't see anything amiss. The water supply by hose is fine I'm sure - it's fed from a direct mains-fed tap.
Any advice ? Thanks David
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I wondered about a partial blockage in

Yes, it does sound like that. If there is back pressure the pump detects it and switches off, e.g. when you release the trigger.
Rob Graham
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Ours does this on 2 occaisions a) when the inlet filter is blocked b) when the nozzle is blocked where it joins the gun
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Usually when this happens its because you have a small bit of grit in the nozzle which is causing the pressure to rise past the relief valve setting.
Best way is to remove the lance from the trigger or nozzle from lance (if possible) and clean it by applying water backwards through the nozzle. Or use some bristles from a washing up brush. Don't use wire!
Tim..
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Thanks for the advice, all. Have checked the inlet filter where the garden hose attaches - perfectly clean. Had a prod with some bristles as suggested, but have also discovered I can actually look down the nozzle of the lance and see daylight right through it, and so can confirm visually there are no blockages there.
So I'm a bit (a lot) puzzled. Any further ideas anyone?!
Could it be faulty machine? Its a recent enough purchase to be returned to the supplier, but I don't want to do that unless it's a genuine fault.
Might the fact that I occasionally experience the problem with the twirly wand be explained by differential pressures in the two wands?
Thanks David
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PS... Further to my post of an hour ago, the pressure pulsing problem is no evident most of the time with my twirly lance as well. I feel a trip to B&Q coming on! David
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wrote in message <snip>

on
Sorry, I joined this late. I agree with Huge - mine does this all the time if I use it on too long a bit of hose - a more direct connection fixes it - also if the pressure is down. Never mind, sounds like you got a replacement anyway!
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I have a Karcher as well. I have also been having pressure problems.
My normal routine begins with running water through the section of hose before connecting it to the Pressure washer, to clear any crud and air. Remove all kinks and try to make the hose as straight as possible. Similarly make sure the washer gun hose is also as straight as possible. This normally resolves really bad pressure problems or the switching on/off cycle. However mine has started leaking water out of the plastic vents as well now. Anybody know what this is? I suspect a gasket of some description needs replacing.
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snipped-for-privacy@hotmail.com (David) wrote:
Hello David

Similar problems with a Sthil. Can often be fixed by raising the lance right up in the air whilst activated.
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