Pressure washer starting and stopping

[ColeyS1]

Guys any idea what could be causing it to stop and start ?
https://1drv.ms/v/s!AoIHLHWc2o66baD4CxjG5sly_iA
I bought it years ago for my dad to use and after a year of him not using it I thought I'd use it. It kept starting and stopping which I put down to the unheated garage causing water inside to freeze and blowing all the seals.
I tried a softly softly disassemble and swapped the capacitor with an identical pressure washer I use for work- its 150% not a capacitor issue ;@) I cleared out my shed at the weekend and thought I'd go guns blazing at taking it apart. I was doing well until I noticed what looked like kettle scale on some of the metal components.

when I pushed the micro switch it caused these 3 piston things-

To run continuously. I started believing it could be fixed. I soaked the bits in white vinegar but nothing has changed.I don't need it but its began to niggle me again that perhaps it could be something simple. I couldn't quite figure out what causes the micro switch to become pressed- a demand of water/release from the gun ? Any ideas chaps?


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[RogerS]

I'm not sure what the issue is, Coley. Are you saying that when you turn it on, press the release handle on the lance then the water just squirts out in pulses, as it were ? The pump going on and off rather than run continuously until you release the handle ?

I had a similar problem on my Nilfisk and fixed it by simply permanently bypassing the pressure switch aka microswitch so that it was permanently on and then using one of those remote on/off dooberries and so turning the pressure washer on/off from the remote in my pocket. Bit of a faff, I agree, but as I use it so infrequently and there is no guarantee that a new one won't eventually nadger up like my current one, it works for me.

 

[Eric The Viking]

I'm on my second Kaarcher industrial-grade pressure washer. The first one managed roughly 20 years but finally gave up last year when seals blew and the motor kept filling with water (about 2 litres - it worked fine for about 15 secs each time it was drained and dried, then it tripped the ELCB on the circuit )

I had it apart several times during its life. The three pistons you show are the pump (in line with the motor axis). There should be corresponding one-way valves (I think those are at right angles in another pic). I don't know the exact design of yours.

If you go beyond those three pistons you'll probably find an oil-filled (half-filled - it's splash lube) chamber with a rotating paddle - elliptical disc on a slant - driven directly from the motor shaft (probably - mine was). That hits the other ends of the pistons to move them.

I found two issues with mine: Firstly the non-return valves leaked, so it couldn't achieve full pressure: as one piston pressurises, the other two are emptying and refilling, so a leaking valve robs pressure from its neighbour. Secondly, there is a pressure-operated microswitch, which on mine was prone to jamming.

Like you, I cleaned what I could and freed-off the microswitch's small piston. IIRC I got new O-rings from a Kaarcher spares place: bingo! All worked nicely again. I lubricated the small slidy bits with Vaseline which helps with the corrosion and keeps the O-rings in better condition. My old lance has a pressure gauge built into the handle, which is very handy (I can still use it - the gauges aren't fitted to modern Kaarcher kit, AFAIK).

But... The other issue was the water supply. Modern outside taps are fitted with non-return valves, to prevent your pond water being syphoned into the drinking water supply. These, and any "water stop" arrangements in the hose couplings themselves are enough to damage bigger jetwashes. They restrict the flow and cause cavitation in the pistons (the water boils momentarily).

It would be quite a bad idea to fit outside taps without non-return valves (er, I expect), and I couldn't possibly suggest you do it, but you do need to make sure that the pump is fed by a high-pressure high-volume water source, as high as possible in both cases. Even coils in the hosepipe make a difference to mine.

The symptoms for mine when it had "issues" with the incoming water were usually stop/starting or running but not achieving proper pressure (and making a funny noise, which was the cavitation happening). So check that too, otherwise you'll be chasing your tail.

The new unit has a brass pump assembly. My first one was a "white metal" casting like yours, and prone to corrosion (we're in a hard water area, which makes matters worse). I don't know what the official approach is to laying-up when they're out of use for a while, but there ought to be a way of purging the water and, say, filling with some sort of chemically neutral liquid instead. I'd guess boiled distilled water would do it, probably, but how you might get it into the pump I can't say. I havethe same problem with my airless spray gun - paint will clog it, but water will corrode it!

The one I now have is this (below): It's OK (and it was hammered hard last year stripping limewash from the house), and the new lance design is much more comfortable for long periods (and modular), but I'm not thrilled by the lack of an on-board detergent tank. That said, the hose connectors are much more rugged and overall I'm pretty pleased with it. I also have an adaptor for the pump that lets me use the old lance and accessories (the standard Kaarcher bayonet used in their consumer stuff), which is handy as that has a drain-jetting hose, which has saved probably thousands in call-outs over the years, and some useful different designs of lance.

It does get hot though. The old one would run for hours at a time without problems, but this one did get a bit toasty at the height of last summer.

 

[Eric The Viking]

Tip: if you do buy a replacement, keep the plastic caps that come with the different parts carefully. They protect those male brass threads (on the lance and the two on the pump), and stop the pump being incontinent all over the garage floor (DAMHIKT).

 

[ColeyS1]

I'm not sure what the issue is, Coley. Are you saying that when you turn it on, press the release handle on the lance then the water just squirts out in pulses, as it were ? The pump going on and off rather than run continuously until you release the handle ?

I had a similar problem on my Nilfisk and fixed it by simply permanently bypassing the pressure switch aka microswitch so that it was permanently on and then using one of those remote on/off dooberries and so turning the pressure washer on/off from the remote in my pocket. Bit of a faff, I agree, but as I use it so infrequently and there is no guarantee that a new one won't eventually nadger up like my current one, it works for me.

That's exactly it Roger. Trigger pressed and pulses of water instead of constant flow. I did try a cable tie on the little pressure switch but exactly the same results.

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[Eric The Viking]

That's most probably incoming water pressure.

Check the whole supply, if necessary as far back as the stop ****, in case there are flow restrictions (hose, tap, non return valves (hint: can fail if teased out with a screwdriver), and any isolating "service" valves inside the premises).

 

[ColeyS1]

If you go beyond those three pistons you'll probably find an oil-filled (half-filled - it's splash lube) chamber with a rotating paddle - elliptical disc on a slant - driven directly from the motor shaft (probably - mine was). That hits the other ends of the pistons to move them.

I found two issues with mine: Firstly the non-return valves leaked, so it couldn't achieve full pressure: as one piston pressurises, the other two are emptying and refilling, so a leaking valve robs pressure from its neighbour. Secondly, there is a pressure-operated microswitch, which on mine was prone to jamming.

Like you, I cleaned what I could and freed-off the microswitch's small piston.

Thanks ETV. When I was in full strip down mode I did find a little oil start leaking out so quickly tightened the bolts up again. Sounds like you understand the inner workings fairly well !!

The microswitch is pushed by a small brass piston as you mentioned- is it meant to be fairly free to move or really really hard ?

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[ColeyS1]

Tip: if you do buy a replacement, keep the plastic caps that come with the different parts carefully. They protect those male brass threads (on the lance and the two on the pump), and stop the pump being incontinent all over the garage floor (DAMHIKT).

All the connections on the makita washer are plastic- that probably says something about its quality ! lol

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[ColeyS1]

That's most probably incoming water pressure.

Check the whole supply, if necessary as far back as the stop ****, in case there are flow restrictions (hose, tap, non return valves (hint: can fail if teased out with a screwdriver), and any isolating "service" valves inside the premises).

But the thing is the identical pressure washer works fine ? Could that suggest a pressure related issue inside the washer itself rather than the supply to it ?
The drain flushing attachment sounds very very very very very very interesting. I wasnt aware such a thing existed for pressure washers- thanks for that.

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[Just4Fun]

The drain flushing attachment sounds very very very very very very interesting. I wasnt aware such a thing existed for pressure washers- thanks for that.

I got one from Lidl. It supposedly fitted umpteen common pressure washers but it didn't fit mine. I was able to cobble together an adaptor though and it has worked fine. A useful buy for not much money so worth keeping an eye out for when it comes round again.

 

[Eric The Viking]

The microswitch's piston operates at full pressure WRT the outside atmosphere. The one on my old Kaarcher was stiff-ish, but moved easily with a pair of needle-nose pliers on it, if you see what I mean.

If they are _identical_ pressure washers I can understand what you say, but if they've been used differently, and there's corrosion in one but not the other, that might explain it.

All I can say is that both the old and new Kaarchers I have are (were) seriously picky about incoming water pressure/flow. It's the first thing I'd check, if only to cross it off the list.

You need safety goggles for the drain jetting system though, and make very sure you have it properly in the pipe before switching on. DAMHIKT...

 

[DrPhill]

It would be quite a bad idea to fit outside taps without non-return valves (er, I expect), and I couldn't possibly suggest you do it, but you do need to make sure that the pump is fed by a high-pressure high-volume water source, as high as possible in both cases.

IKNATB would it be possible to have a large slightly flexible vessel between the tap and the pressure washer to act as a 'capacitor' for water, smoothing out the pulses that occur when the washer 'overdraws'? Not sure if such a thing exists.....

 

[ColeyS1]

The microswitch's piston operates at full pressure WRT the outside atmosphere. The one on my old Kaarcher was stiff-ish, but moved easily with a pair of needle-nose pliers on it, if you see what I mean.

If they are _identical_ pressure washers I can understand what you say, but if they've been used differently, and there's corrosion in one but not the other, that might explain it.

All I can say is that both the old and new Kaarchers I have are (were) seriously picky about incoming water pressure/flow. It's the first thing I'd check, if only to cross it off the list.

You need safety goggles for the drain jetting system though, and make very sure you have it properly in the pipe before switching on. DAMHIKT...

Thanks ETV, I'll mull it over.

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[flying haggis]

It would be quite a bad idea to fit outside taps without non-return valves (er, I expect), and I couldn't possibly suggest you do it, but you do need to make sure that the pump is fed by a high-pressure high-volume water source, as high as possible in both cases.

IKNATB would it be possible to have a large slightly flexible vessel between the tap and the pressure washer to act as a 'capacitor' for water, smoothing out the pulses that occur when the washer 'overdraws'? Not sure if such a thing exists.....

i thought some pressure washers could operate from a tank of water, ie sucking it in as required, might be worth a try with a bucket