Stihl Power Washer problem

[ianp5852]

Help!! I have a problem with my RE108 pressure washer. On initial use, it will work as expected. When the trigger is released the motor switches off as expected. When trigger is pulled again water will come out of the lance at mains pressure but motor will not restart.

The unit has been at the local dealers for over a week and they cannot replicate the problem. They suggested that the 'waterstop' connector I used may be at fault. I have now tried with different straight through connectors and, indeed, different shorter hose on the mains supply. The problem still persists although I have found that by nearly closing the tap to which the (various) hoses are connected will allow the motor to restart when the trigger is pulled but then after a few seconds the flow is clearly restricted that the washer seems to be 'hunting' for more water. It seems to me that the pressure (or is it flow) switch is rather too sensitive. I believe this is adjustable but do not know where to start! Incoming filter is clean - and has been all along.

Our mains water is supplied through a relatively new but longish service pipe (about 300 m) which we installed a couple of years ago to help improve flow rates. The local pressure, prior to installation, was approx 7bar according to water supply company and the flow was considered 'acceptable'. The flow has been increased significantly since we installed the new non-shared service pipe. Hence, I have no real concerns about the mains supply being in any way unusual.

Any ideas on next course of action? TIA Please reply to group - email address is not monitored Ian

[Fredxx]

Before I read this paragraph my immediate thought was a high mains pressure.

It is possible to get pressure reducing valves to sort this problem out.

[The Medway Handyman]

Not familiar with that particular model, but 30 years in the pressure washer game....

'Waterstop' connectors do cause problems with pressure washers because the valve is 'sucked' shut by the pump, reducing the water supply, but they shouldn't cause that particular problem.

It would, the machine needs at least 440 l/hr, any less & it will 'hunt'. Any more water isn't a problem.

It will almost certainly be a pressure switch. Flow switches are rare. Been trying to find a parts list online with no success. Don't spose you have one?

Pressure switches on HPC's are very basic things. Basically a piston & spring. When the trigger is shut the piston is pushed up (or down, or sideways, whatever) by the increase in pressure and the end of it touches a microswitch which breaks the circuit to the contactor running the motor.

When the trigger is opened the pressure drops and the spring returns the piston, allowing the microswitch to 'make' again & the motor re starts.

Sounds like the piston is sticking in the 'up' position & the spring isn't making it return. When you starve the machine of water its returning as it should.

Take the cover off & you should see something on the pump head with a cable going to the electrics box. That will be the pressure switch. Possibly damaged/weakened spring. Most have adjustments, but don't go mad, a slight adjustment will have a big effect.

Any adjustment that affects the 'on' pressure will also affect the 'off' pressure.

Good!

Incoming water pressure doesn't really matter, only the flow 440 l/hr is

7.3 l/min - time it with a graduated bucket if you want to check.

[The Medway Handyman]

Reading that, I've reconsidered my reply about mains pressure not mattering. That could be the problem, the incoming 7 bar might be stopping the piston in the pressure switch returning.

Simple way to find out - use a short hose & suck water from a container - water butt or similar. If it works properly your mains pressure is the problem.

Thanks Freddxx :-)

[ianp5852]

Many thanks to both TMH and Fredxx. I have tried the above suggestion using hose and bucket. The machine works flawlessly! So , I guess, its off to BES for a pressure regulator. I'd never thought of our rural water supply as being too high pressure

- we are on a hill overlooking Vale of York - but the reservoir which feeds us is significantly higher! Thanks again for your help. I will also pass the info on to the local dealer. Please reply to group - email address is not monitored Ian

[Dave Liquorice]

There must be a water stop connector that doesn't work like the two I have, both compatilble hozelock fittings but not hozelock branded. In these the valve is pushed open by the male being inserted, no way can these be sucked shut, they are physically held open by the male.

Also how would water flow through a water stop valve that could be sucked shut? The normaly flow would shut it... if there was a spring to resist the flow, it wouldn't reliably stop the flow with low pressure/flow rates.