This DIY repair guide explains how to replace a pressure washer chemical injection valve. The chemical injection valve draws detergent into the pump when you use a low-pressure nozzle for cleaning. A worn or damaged chemical injection valve won’t pull detergent into the water stream. If the pressure washer isn't spraying soapy water when it should, first make sure you’re using a low-pressure nozzle and the siphon hose isn’t clogged. If so, replace the damaged chemical injection valve with the manufacturer-approved replacement kit. The chemical injection kit includes the O-ring and all parts needed for the repair.
Follow the steps in this repair guide to install the chemical injection kit in common Craftsman, Generac, Briggs & Stratton, Husqvarna and Troybilt pressure washers.
Disconnect the spark plug
Disconnect the spark plug wire from the spark plug.
Remove the chemical injection valve
If detergent is in the detergent reservoir, clamp the chemical injection hose near the chemical injection valve.
Use an open-end wrench to turn the chemical injection valve counter-clockwise and remove it.
Clamp off the chemical injection hose.
Pull the chemical injection hose off of the valve.
Remove the chemical injection valve.
Install the new chemical injection valve
Install the O-ring from the kit on the new chemical injection valve.
Lubricate the O-ring with silicone lubricant. Thread the new chemical injection valve into the pump and tighten. Reconnect the chemical injection hose.
Release the clamp from the chemical injection hose, if used.Tip: If you have a torque wrench, tighten the new chemical injection valve to 10-12 ft.-lbs. or torque.
Install the new chemical injection valve.
Reconnect the chemical injection hose.
Reconnect the spark plug
Reconnect the spark plug wire to the engine.
Check pressure washer operation
Start the pressure washer and check for leaks. Check for proper detergent draw through the new chemical injection valve.
Air in the inlet water supply can damage the check valves. If the pump won’t build up pressure due to damaged check valves, follow these steps to replace the check valves.
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The pump can be damaged by air in the inlet water supply or by chemicals that remain in the pump body after using the chemical injection system. Follow these steps to replace a damaged pump.
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