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high pressure washer won't run

Posted by heyduke none (My Page) on
Wed, Jun 5, 13 at 3:35

I have a nilfisk c100.5 high pressure washer that runs for a couple of seconds when turned on then cuts out. I have checked the air filter and also made sure that the water line is clear. The machine has been used for not much more that 10 total over the past few years and it worked fine until last week.

If this is not the proper place to post this message, please let me know where I might be better helped with the problem


Follow-Up Postings:

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RE: high pressure washer won't run

only suggestion I can give when I had elect. pressure washer sometimes air would get trapped in it and cause what you are describing. I would make sure all the air is out of the water hose before you connect it (turn it on and let water run till good stream) connect it pull the trigger see if you an get the air out of the machine, then try to turn it on. Hopefully just air trapped??? I never ran mine unless I had good water supply with all the air out of the hose from the house and the unit. I know most elect. (also Gas powered) pressure washers heat up very fast it no water is flowing and may damage the pump if ran too long without water flow to cool it..


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RE: high pressure washer won't run

Yeah I agree with rcmoser , Many models will automatically turn off if they have this problem.

Also some washers have a reset button that will click itself off if there is any problems with the electricity. Are you using it with an extension lead.... its not a good idea to use a pressure washer with an extension.

Is there water leaking out from anywhere ?

Let us know if any of this works heyduke


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RE: high pressure washer won't run

I appreciate the replies. I made sure all the air was out of the water supply. Then connected to the washer. Without turning on the power, I let the water run through for several minutes. First with the pressure hose off and then with it on. Water was passing through seemingly unobstructed. I then turned on the power and got the one-second sound of a motor starting. Then it stopped. Having nothing to loose at this point, I just left the power on and let the water keep flowing through. After about 30 seconds, something got powered on because there was a sound. But it lasted less that a second (and it certainly did not sound like the compressor). After another 30 or so seconds the same thing again. And then one more time after that. Tried toggling the on-off switch a couple of times (trying simple solutions). That did not change anything. Conclusion: power is getting to the motor, but it just won't catch. If it matters, it seems that the water coming out of the machine is slower that what is going in.

Again, thanks for your input.


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RE: high pressure washer won't run

OK, I took it a step further. I took the machine apart and found what is apparently called a "start/stop valve". It is mounted into the compressor section with a nylon-looking, hexagonal nut (which does not come off easily). Out of the center of that fixture is a nylon stud or pin. My guess is that I should be able to move that pin either in or out, but it won't budge. Next step will be to force the piece out the best I can, but I expect I will end up stripping the nut in the process.


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RE: high pressure washer won't run

Hmmm ok ,

Its hard to tell without looking at it personally but just to remove another other doubts...

Have you changed the hose lately going to the pressure washer ?

Is the water that is going to your machine hotter than usual. - I don;t know where you live but for me the first few minutes after turning on the water its really hot because its been solar heated and its pretty close to boiling hot.

Is there any damage to the your garden hose which would cause it to suck in air along with water ?

But it seems you have already looked at these problems so at this stage the damage seems to be done so I am listing potential reasons for the problem and not cures, sorry about that. Usually though ,when the whole pump has broke it will show a lot more symptoms.

If you are having trouble removing that plastic nut try to use a socket set and not a spanner.The spanner will for use cause the side to get wore down.

The "start/stop valve" could be the unloader valve which has a spring inside it to control the pressure.... maybe a surge of air has forced it into its current position where its now difficult to remove.

However I should warn you that if it is the unloader valve that when resetting,it needs to be in the correct setting otherwise its never going to be at the right pressure.

If it was me and I was trying to fix a big gas powered pressure washer I would stay away from it but since its a somewhat cheap electric one and to buy a new pump would almost cost the same as a new pressure washer I wouldn't mind having a play around with it in the hope it works fine again.

Sorry I couldn't be of more help. The electric washers are so picky and if the slightest part isn't doing what its supposed to be doing well then the whole things breaks.

Here is a link that might be useful: I found this earlier... maybe it will help a little

This post was edited by Gav104 on Thu, Jun 6, 13 at 23:09


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RE: high pressure washer won't run

Thank you for taking time to post a reply.

All the hoses and connections seem fine. When connected to the hose, the pressure of the water flowing thru with the machine turned off seems rather weak. I really don't know if it should be coming out stronger.

I think I mentioned that I am by no means a repair person, but I do what I can. And since it certainly would not pay to take the machine in to get fixed, I will continue to play with it. By the way, I am in Denmark.

I would have used a socket if I had one big enough, but I don't. In Denmark, a new socket is ridiculously expensive!

I will check out the link you sent. Thanks again.


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RE: high pressure washer won't run

From reading the link over that I sent you they mention unscrewing the unloader valve and turning the machine on with it connected to the water and using a towel over the unloader valve to let the pressure from inside the pump force the spring the rest of the way out and then smearing it with grease and quite a few people have said this helped.

If you can find a way to unscrew that plastic nut that will really help but of course if you were to damage the nut using a spanner you would not be able to use a socket set on it anyways.......maybe ask around to see if you can borrow a socket and wrench beside damaging the plastic nut any further.


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RE: high pressure washer won't run

Oh, I have been very careful about using a spanner. So far, I have not damaged the nut (much). I will try to dig up a socket. Gotta be cheaper than a new machine!


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RE: high pressure washer won't run

Might be a long shot, but my gas pressure washer was doing a similar thing last week. First use of the season here. Really weak stream when the engine was off and getting the air out of the system and nothing at all with engine running.

I ended up taking the sprayer / wand apart and found a screen that was plugged with mineral deposits from the water over the years. Cleaned that up and all was back to normal.


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RE: high pressure washer won't run

Well, I finally got around to tearing the thing apart. Everything looks OK. Valves clean. Unloader valve seems to work right. Noting jammed or stuck. Put the sucker back together and started it right up.... The motor ran for max. 2 seconds then died out. Looks like we go shopping for a new unit this weekend.


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RE: high pressure washer won't run

Ah that sucks, I thought we were on to something with the unloader valve.


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