Power washer fault, help please

Not sure if yours is the same but on my alty pressure washer the spring loaded plunger you describe switches off the pump when the water in the system is up to pressure. When you press the trigger on the lance the pressure drops fractionally the plunger returns and the pump starts (This is how I think that it works anyway)

When my pressure washer showed the same problem it was because the plunger had stuck in the pump of position. I had to dismantle it clean it up and WD

Tony

Hi Chris

First of all, I assume that when conected to the tap water flows through the machine and the nozzle isn't blocked? I don't know this particular machine, but.....

Normally these machines switch on and off with a simple pressure switch. Assuming the working pressure is 100 bar, there will be a spring loaded valve set to (say) 110 bar. When the trigger is closed, the line pressure increases, forcing the valve to open.

The valve has a piston or rod attached and when the valve opens the rod moves. The rod pushes a micro switch and breaks the circuit, so the motor stops. When you pull the trigger, the line pressure drops, the valve closes, the rod moves back and the micro switch makes the circuit again.

If the machine wont start it's usually because;

Valve is stuck in off position - very common if the machine hasn't been used for a while.

Valve set to lower than line pressure.

First thing to do is check that the spring loaded plunger is free to move & not stuck. Can be limescale or detergent residue, so if you can get it apart, clean it, lubricate it then it should work.

Failing that, try adjusting the plunger length. A small adjustment makes a big difference, so don't go mad! Or the microswitch is u/s. If the motor hesitates it's posible the start capacitor is faulty

My guess is that the plunger is simply stuck/sticking.

Dave

That sounds a fairly likely sort of explanation, thanks, I'll get daring and take it apart some more and give it a good clean.

Yes, flows as freely as it always did.

It stopped working after I'd been using it for a while so that seems unlikely.

Thanks for the explanation of how it works, all pretty straightforward really. It definitely feels to me as if the microswitch is simply not being operated. The plunger seems quite free though so maybe I'll take a look at the mechanics of how the plunger operates the microswitch. There is a minor added complexity in that the washer has a rotating 'switch' with OFF, LOW and HIGH positions, this has a shaft that goes into the same place as the plunger (e.g. where the microswitch is) so it may have some clever interaction with the plunger to adjust the output pressure.