Pulsing pressure means the pump is not receiving water consistently, cannot hold its output, or the pressure-control system is repeatedly loading and unloading. The timing of the pulse is the first useful clue: rapid vibration at the lance differs from a machine that builds pressure, drops away and then recovers.
Rule out water starvation first
A restricted tap, kinked inlet hose, blocked inlet filter or air leak on a suction setup can starve an otherwise healthy pump. Test with a known adequate water supply, clean filter and the correct inlet hose. If the machine draws from a tank, confirm every suction connection is airtight even when no water visibly leaks out.
The nozzle changes the whole pressure system
A worn nozzle usually lowers pressure; a nozzle that is too small can overload the pump and make the unloader hunt. Check the fitted nozzle against the machine’s intended pressure and flow instead of choosing by thread size alone.
When the fault is inside the machine
- Debris or wear in one or more pump valves.
- High-pressure seals bypassing internally.
- An unloader sticking or set incorrectly.
- A trigger valve that does not open cleanly.
- Air entering detergent or suction pipework.
Information that makes diagnosis faster
Note whether it pulses from cold, only after heating, at every pressure setting, and with another hose or lance. A short video of the gauge and outlet sound can be useful with the model-plate photograph.
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Send the model and symptoms, or ask us to help match a machine to the work.