How to repair a ‘doesn’t pump’/’doesn’t high pressure pump’/’delayed high pressure’ faults on ELECTRIC Karchers (may be similar on other brands)
Karcher say it cannot be repaired, and to buy new... Poppycock!.. it doesn’t even need any spare parts... it’s all down to a sticky spring loaded plunger, hidden inside a bit of plastic that pulls apart!
Now I cannot advise on how to dissemble YOUR particular model of karcher, except to say that you will need a FULL set of star keys.. I recommend the ones with a T bar at the top for leverage... plus a Philips screwdriver and a pair of long nose pliers.. and an ice cream tub to keep the bits safe!.. for the lubricant, you can get away with Vaseline jelly, but as some gaskets are perished by this, I recommend going to a divers shop, and buying a small tube/bottle of divers lubricant.. the stuff they use for zips, etc. As it is safe to use on neoprene and rubber and is quite cheap (around £3 for a small bottle with brush inside). Karcher like to hide star screws under other parts.. check EVERY hole for a star screw.. if you are having problems getting the yellow case apart, chances are that there is something still on the yellow case, and under that is a star screw you couldn’t see... DONT force it.
If you have an onboard hose reel, you will find a ‘flap’ that appears to have no purpose... PUSH that flap and whilst pushing, twist the outer part of the hose reel clockwise,, it will come away.
Before you start to dissemble.. note that you will be looking at the entry point for the SOAP .. (yes strange but true, the high/low pressure is dictated by a gizmo in there!)Basically when you take off the outer shell, (almost all T27 star screws, but some of different T sizes, and Philips screws secure parts that go through metal) you will find a big motor, a plastic box full of electrics, (please unclip the cover ..outer clips first, then inner clips.. and set aside because there’s a bit on the lid that will get in the way of the next bit) and 2 sets of 4 allen bolt heads (star keys also undo Allen bolts) on one end.. carefully remove the engine (please make sure it isn’t plugged in!) and stand it on the fan end, or some other orientation, so that you can access the allen bolts just below where the soap inlet hole is... these bolts simply secure a metal cover that holds all of the ‘pump head’ onto a set of 3 mini pistons... be careful to remove the triangular pump head in one piece.. and ensure that all 3 rubber bushes come off the little pistons, and remain inside the pump head... that way it makes it easier to put it back on at the end! TRY not to pull the two main sections of the pump apart (in the middle) as there are 3 small springs, 3 small white water flow heads, and a thin gasket that might fall out and get lost.. if it does come apart, the springs sit ON TOP of the white bits, and the gasket sits on the very outside edge lip.
Back to the pump head...You will find a brass rod being held on to by a bit of plastic with a Philips head bolt, and a square nut on the other side.. undo this and set aside.
Now with the long nose pliers, and holding the plastic pump head in your left hand (if you are right handed, or right hand if left handed) pinch hold of the short neck of the soap inlet that goes ‘straight’ into the pump.. NOT the bit that bends off at 90 degrees.. and using your thumb as a fulcrum point, pull the inlet nozzle off... it fits so well, it may seem that it is welded as a single piece, but it isn’t.. it simply pushes in/out as it is held in place by the metal cowel you took off at the start... inside here you should see a white disc.. if it hasn’t jumped out at you, it proves the fault!.. push the brass rod in (I used the side of my pliers) and it will come out.. white head with O ring around, spring behind that, white disc, then one or two tiny O rings on the brass rod.. THIS is the cause of your fault! Clean off any old white cheap grease they used (if there is any left) and lubricate with the divers lubricant or Vaseline and reassemble in reverse order... when you put that plastic clamp back on the brass rod, the brass rod should JUST be flush with the hole it comes through... once you have the soap inlet back on, check that the rod moves quite freely.. no jerkyness.
BUT remember that lid to the electrics?.. look inside.. you will find that it has a toggle lever operated by the on/off switch of the machine.. and there is a little ‘joystick’ nodule that sticks out of the side.. well AFTER you have resecured the 4 allen bolts, put the electrics lid back, guiding that joystick nodule so that it sits inside the plastic clamp that is on the brass rod.. do the inner clips up first, then the outer.
Reaasemble the case of the machine
Check you don’t have any left over parts in the ice cream tub!
Problem solved!..
How does this solve the problem?.. easy.. when you adjust your nozzle or attachment from low pressure to high, it causes a ‘backpressure’ in the pipe that pushes that now greased up white disc up to cut off the soap.. and it also operates the toggle that presses the motor power button inside the electrics box. When it sticks, either fully, or partially, you only get low pressure, or a delay as it slowly cuts off the soap, which reduces the water flow through, and thereby triggers the high pressure.
Julian Pearson
May 2011
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