Why is my high-pressure washer pulsing?

When pressure causes problems

/ Inspirations


Estimated reading time 3 minutes

Is your pressure washer not reaching maximum pressure? If your high-pressure washer has no pressure, it is likely due to a problem that you can fix quickly without any expert intervention:

  • Make sure that the lance is in the standard high-pressure working mode, not on the low setting, which is the mode you want to set for spraying detergent.

  • Check that the water supply hose is not leaking, blocked, tangled or overly long.

  • Make sure the water supply is adequate: the mains water tap may not be fully open, or the flow rate may be lower than the minimum required flow (consult the user and maintenance manual supplied with your high-pressure washer).

  • Clean the inlet water filter, which might be clogged due to limescale or other impurities, thus reducing the flow rate of incoming water.

  • Inspect the jet nozzle at the tip of the lance, which may also be responsible for strong pressure fluctuations, as indicated by a pulsing flow of water from the high-pressure washer nozzle. If it's dirty or encrusted with limescale, clean it with the supplied pin. If it is worn, replace it with an original spare part. Do you have an Oleo-Mac high-pressure washer? For any doubts, the experts at your nearest service centre are at your disposal.

After all these checks, does the problem still persist? If your high-pressure washer still won't build up pressurise, the cause could be:

  • A faulty pump , which is the component of the machine that pressurises the water: its parts (gaskets, valves, pistons, etc.) can wear out, in which case they must be changed.

  • Problems with the bypass valve, which is the safety device that limits and regulates the pressure of the jet.

For any interventions on the pump or bypass valve of an Oleo-Mac hot or cold water high-pressure washer, you can entrust the job to a technician at one of our service centres.

But what should you do if your high-pressure washer works in fits and starts? It might be that it keeps restarting by itself due to the automatic stop system (also known as total stop). Total stop is a safety device that automatically stops the high-pressure washer when you let go of the gun trigger. Total stop also causes the high-pressure washer to restart as soon as you press the lever again; it does not turn off in the meantime, but is effectively still running. Therefore if the high-pressure washer is working in fits and starts, in other words, it keeps starting and stopping by itself without you pulling the trigger, then:

  • The cause could be excessive water leaking or dripping along the delivery circuit, i.e. between the pump and the gun. The total stop system misinterprets the drop in water pressure due to leaks as squeezing of the gun trigger, so it restarts the high-pressure washer to re-pressurise it. To resolve the problem, check the fittings, seals and hoses of the high-pressure washer and replace them if necessary.

  • The reason might be the gun itself, if it does not shut off properly and thus lets water leak out. See the previous point for an explanation of what happen as a result. In any case, the solution would be to replace the gun.

If your electric high-pressure washer stops suddenly during normal operation, it means that a mains power safety device or a protection system of the high-pressure washer itself has been triggered due to a current overload or overheating of the electric motor. In this case, follow the instructions in the user manual according to the specific circumstances. If the high-pressure washer is petrol-driven, like the Oleo-Mac PWX 200 C, the problem may be with the engine: fuel tank empty, inadequate fuel quality, spark plug electrodes need adjusting, spark plug needs replacing, or engine flooded.

Many of the solutions we have suggested for fixing a high-pressure washer that won't pressurise or that works in fits and starts, are typical measures for efficient operation or usual routine maintenance steps, which you can also find summarised in this focus article on high-pressure washer maintenance. You can click the following link to watch a video with key steps for correctly using one.

The water pressure in a high-pressure washer provides not only cleaning power, but also mechanical force for clearing clogged drainpipes and blocked drains, or for sandblasting painted, rusty or dirty surfaces, and so on. Don't have a high-pressure washer yet? This guide highlights their many uses and provides tips on choosing one.

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