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In short
Simpson's manual says a clogged nozzle can make the pump pulsate and change the spray pattern, and that if it isn't cleaned, excess pressure can build up and damage the pump or accessories. Its troubleshooting chart lists "pump or nozzle pulsates" with one cause: nozzle obstructed. Clean the tip first.
Replacement nozzles with 1/4-inch quick connect:
Simpson 80145 5-Nozzle Set Simpson 80143 Turbo NozzleHow to clean a pressure washer nozzle (Simpson's steps)
- Shut off the pressure washer.
- Turn off the water supply.
- Point the gun in a safe direction and squeeze the trigger to release the pressure.
- Set the trigger lock.
- Remove the nozzle from the quick connector.
- Clear the opening with the nozzle cleaning tool that came with the washer.
- Back-flush: run a garden hose into the nozzle's outlet for at least 30 seconds.
If the tip is damaged or won't clear, replace it with the same orifice size. See the size chart.
Low or no pressure: other causes on Simpson's chart
| Cause | Fix (Simpson manual) |
|---|---|
| Nozzle clogged | Clean it with the steps above |
| Air trapped in the pump or hoses | Purge the pump as the manual describes |
| Not enough water supply | The supply must give at least 5 GPM at 20 PSI |
| Water inlet screen clogged | Clean the inlet screen |
| High-pressure hose too long | Keep it under 100 feet |
| Engine choke left on (gas models) | Move the choke to the NO CHOKE position |
Check before every use
Simpson says to inspect nozzles before using them, and to check and clean the water inlet filter before each use. Never run the washer without the inlet filter installed.
Don't run it with a blocked nozzle. Simpson warns the extra pressure can damage the pump. For repairs beyond cleaning, the manual recommends an authorized service center.
How we work: causes, fixes and cleaning steps come from Simpson's operator manual. Your own washer's manual comes first. Sources are listed below.
Questions people ask
Why is my pressure washer pulsing?
Simpson's troubleshooting chart lists an obstructed nozzle as the cause of pump or nozzle pulsing. Clean the nozzle.
How do I clean a clogged pressure washer nozzle?
Simpson says: shut off the washer and water, release pressure, lock the trigger, remove the nozzle, clear it with the cleaning tool, then back-flush with a garden hose for at least 30 seconds.
Why does my pressure washer have low pressure?
Simpson's troubleshooting chart lists a clogged nozzle, air trapped in the pump or hoses, a water supply under 5 GPM at 20 PSI, a clogged water inlet screen, a high-pressure hose of 100 feet or more, and on gas models the engine choke left on.
Sources
Last checked Oct 23, 2026. Pressure washer spray can cause injection injuries. Lock the trigger before changing tips and release the pressure before disconnecting anything, as Simpson's manual says.
