Symptoms
- Engine keeps running after switching to off
- Electric motor keeps humming after trigger is released
- Machine cycles on and off rapidly on its own
- Have to unplug or disconnect fuel to stop it
Likely causes
- CommonStuck or worn ignition kill switch (gas models)The switch that grounds out the ignition to stop the engine can fail internally and stop making contact.
- CommonStuck pressure switch (electric models)Electric pressure washers use a switch triggered by pressure to start/stop the motor; if it sticks, the motor won't shut off.
- PossibleDebris or corrosion in the switch mechanismDirt or moisture intrusion can prevent a switch from making or breaking contact properly.
- PossibleUnloader valve stuck, keeping pressure switch engagedOn electric models, if pressure never drops after releasing the trigger, the motor thinks it should keep running.
What to do
- On gas models, if the engine won't stop with the switch, pull the spark plug wire off as an immediate way to kill the engine, then address the switch before running it again.
- On electric models, unplug the unit immediately if the motor won't stop after releasing the trigger.
- Once stopped, inspect the on/off switch or kill switch for visible corrosion, looseness, or damage.
- For electric models, check whether pressure is dropping when the trigger is released; if not, the unloader valve may be at fault rather than the switch.
- Clean light corrosion from switch contacts if accessible, or replace the switch if it's clearly worn or unresponsive.
- Do not continue using the machine regularly with a failing shutoff switch, since this is a safety-relevant control.
- If the switch or unloader valve isn't a simple swap for you, have a small-engine or appliance repair technician replace it.
Tools and parts
- Pliers (to pull spark plug wire on gas models)
Engine kill switchSearch: “small engine ignition kill switch”
Pressure washer pressure switchSearch: “electric pressure washer pressure switch”
When to call a pro
Have a repair technician replace a failing shutoff switch promptly rather than working around it, since it's a safety control.
Safety
Use caution
A machine that won't shut off is a safety issue; stop it immediately (unplug or disconnect the spark plug wire) and don't use it again until the switch is fixed.