Nilfisk 140.3 pressure washer fix (likely similar for other makes and models)

[tobers]

I bought my Nilfisk 140.3 pressure washer after recommendations on here.

It was great for about a year. Then it randomly wouldn’t run, then it would, then it wouldn’t etc. Extremely frustrating. The symptom was that, with the washer plugged in and on, and water connected, when switching on the normal loud thrumming pump sound was sometimes absent. It normally thrums for a second or so when switched on.

Sometimes though, it would thrum when switched on. And then it would work fine for a while ie you trigger the lance and the pump triggers and it power washes anything very nicely. Then you let go of the lance trigger, move around the car/patio etc and when you pull the trigger again the pump just wouldn’t start. Wait a bit, kick the machine a few times, and it then might start, but often wouldn’t. Random and intermittent. Very frustrating.

Today I decided to sort it out. I’m posted here to help any other victims to save some time. I couldn’t find anything on the internet to help.

I figured there must be a switch somewhere that sensed water pressure from triggering the lance, and then switched the pump on.

I basically unscrewed any visible screws to remove the handle, covers, underside. Basically stripped. First thing to check was the on/off switch. Some of the contacts were a bit loose but the switch worked fine (multimeter continuity test). I tightened up the crappy spade connectors a bit. Re-tested - same problem.

The pump seemed to spin OK. There was no debris in the inlet. Could be the capacitor (large white cylinder near the on/off switch. But that looked fine and would either run or not - it wouldn’t cause the intermittent issues I was experiencing.

Next to the water inlet was a little white plastic rod sticking out. I couldn’t figure out what this was.

After further investigation, the panel that the power connectors are fixed to has a little microswitch attached to a cable that goes up to the on/off/capacitor switch connector gang. This microswitch is triggered by the little white plastic rod. But it’s usually under a cover that you need to expose by removing another screw (the cover that the water inlet goes through).

Weirdly, there is nothing to hold the microswitch assembly onto the white rod. Figuring this microswitch sensed pressure on the inlet and triggered the pump (from the wiring diagram), I decided it was the cause of the intermittent problems I’d been having. I have no idea why it doesn’t screw or bolt in place. It’s so obvious it will dislodge and cause problems.

So I cable-tied the microswitch in place, reassembled, and everything now works perfectly!

As it happens, I need not have removed every screw and plastic piece. I could have just removed the two screws holding the front cover on (under the unit) and then the additional screw for the panel covering the inlet valve and I would have been able to get to the micro switch.

I hope this helps someone.

Here’s the culprit

Hmm - if you can’t see the image try this link:
https://tobinators.com/blog/wp-content/uploads/2019/04/img_2673.jpg

 

[ktuludays]

Great post. I have a nilfisk and whilst I haven't had the issue you describe I'll keep your post in mind if I ever do.

 

[stealthwolf]

I have the same model and had an issue with it only working intermittently. Turns out it doesn’t like hozelock autostop connectors.

 

[cdbe]

Great post. I have a nilfisk and whilst I haven't had the issue you describe I'll keep your post in mind if I ever do.

Same here. I'll file this one away.

 

[Michael G P]

Just the job...thank you

 

[Kempouk]

(long quote removed)

Hi,
New here and come across your advice as my pw was playing up so followed your NFO but with no joy,
So I did some further investigating on my machine and found that the pump worked just fine with the pressure switch housing removed from the white rod.
This showed me that the white pressure rod was stuck in the out position so as soon as the pressure switch was connected the switch was activated telling the unit not to run as it was under pressure.
I took a pair of long nose pliers and with a fair bit of force pushe the white rod back into the housing.
This resulted in a click as the rod become free and retracted back into the unit leaving about 15mm protruding from the unit.
This inturn disengaged the pressure switch allowing the pump to run as it should .
So this white rod is prone to sticking and in the out position will render the unit usless.
I then put a tiny bit of cilicone geese on the rod and cable ties it back in position using your advice.
To access this you just need to remove the two hex scews from the underside of the unit holding the front feet on the machine,
Then lift the blue cover off,
Then remove 1 hex scrw covering the pressure switch housing and the black pressure switch is located here.
The can be removed by pulling hard and gently up and down as it pops into place.
One the switch is removed you can see the white pressure rod,
This is the problem and needs a pair of long nose pliers and some force to pop it back I to position,
This rod should be protruding about 15mm.
You can flick the power switch on and off to make sure the switch is now free and working as it should.
Then put your unit back together.

 

[Michael G P]

Great update....thank you!

 

[sparkymarka]

(long quote removed)

Hi,
New here and come across your advice as my pw was playing up so followed your NFO but with no joy,
So I did some further investigating on my machine and found that the pump worked just fine with the pressure switch housing removed from the white rod.
This showed me that the white pressure rod was stuck in the out position so as soon as the pressure switch was connected the switch was activated telling the unit not to run as it was under pressure.
I took a pair of long nose pliers and with a fair bit of force pushe the white rod back into the housing.
This resulted in a click as the rod become free and retracted back into the unit leaving about 15mm protruding from the unit.
This inturn disengaged the pressure switch allowing the pump to run as it should .
So this white rod is prone to sticking and in the out position will render the unit usless.
I then put a tiny bit of cilicone geese on the rod and cable ties it back in position using your advice.
To access this you just need to remove the two hex scews from the underside of the unit holding the front feet on the machine,
Then lift the blue cover off,
Then remove 1 hex scrw covering the pressure switch housing and the black pressure switch is located here.
The can be removed by pulling hard and gently up and down as it pops into place.
One the switch is removed you can see the white pressure rod,
This is the problem and needs a pair of long nose pliers and some force to pop it back I to position,
This rod should be protruding about 15mm.
You can flick the power switch on and off to make sure the switch is now free and working as it should.
Then put your unit back together.

What type of GOOSE was that ?

 

[Kempouk]

It's a silicon goose lol.
I'm always getting typos using my phone.
Lol

 

[sparkymarka]

Made me chuckle ...

 

[Kempouk]

And me when you pointed it out,
Lol
Apparently they are quite rare.

 

[Steviebabes1]

Hi All, I have a C110 with the same problem, but I have now cured it, well for now. I found a video on youtube by Leif-Helge Johansen, I think he's Danish, but what ever country he's from, I don't understand a word, but the video says it all. It helped me cure my problem. The link to the video is - Nilfisk start stop ventil - YouTube.

Just for clarification, on my unit, I had to remove the handle, about 4 other screws and remove the wheels (2 screws) to get at 2 screws hidden underneath. Force the black box off gently with a flat blade screw driver, pushing away from the valve housing. Once that is pushed off, undo the not (20mm in my case) and remove the valve and spring inside. Mine looked fine, including the 2 'O' rings. I applied some petroleum jelly to the spring and white rod to make sure there was easy movement. I also checked the micro switch worked in the black housing removed earlier. Put most of the unit back together, but I only used 4 screws for now, just in case and tested the unit, then rebuilt in full. Yes it worked well. Glad I didn't waste my money on a new unit, such an easy fix, but a poor design if this is a regular problem.

Hope this helps and thanks to Leif-Helge

 

[meccomania]

I've had the same problem as the original post. Here's what I think happens..

When you first turn on, the pump starts and the pressure builds up. The pressure bypass (the white piston moving against the spring) opens, allowing the pressure feed to re-circulate to the inlet until the flow and pressure stabilise. This moves the plunger towards the microswitch, but crucially not by enough to open it. After using the lance, when the trigger is released to shut off the flow, there is a slight pressure pulse that is just enough to cause the microswitch to open. The pump stops, the plunger returns to its seated position, but the microswitch fails to close. This is because of the hysteresis in the switch point. i.e. It has to release beyond the point at which it opens in order to close. If you're lucky this eventually snaps shut and the pump runs again - until the next time. So how to fix it ...

Unfortunately there is no adjustment. Although unscrewing the pressure bypass slightly increases the distance between the plunger and microswitch, it also unseats the sealing O-rings causing water leaking everywhere. Even if this does succeed in allowing the microswitch to close, the resulting pressure pulse when it restarts causes it to open again. So it just keeps pulsing on and off. My solution was to cut about 1mm off the microswitch plunger (NOT the pressure bypass plunger). Now when the trigger is released, the pump momentarily cuts out, then resumes.

However, I really fail to see what the microswitch is supposed to achieve. It may mitigate the pressure pulse when the trigger is released, but I would have thought its too late for that. Personally, I think the easiest solution is just to remove or bypass the microswitch altogether. If anyone knows if this is a really bad idea, I would be very interested to hear why. You do this entirely at your own risk !!

As everything it right on the limit of working/not working, stripping and reassembling the bypass probably gives the illusion of having fixed something. It only takes the tiniest change in positions to make it work. It did for me the first time, but the problem soon returned. Now I understand why. Incidentally, I suspect that this may also explain why using a stop end fitting on the hose causes it to pulse. Next time I use it I'll try using one.

Hope this helps ...