This DIY repair guide explains how to replace a pressure washer pump. The pump creates the water pressure for the spray nozzle. Air in the inlet water supply can damage the pump, as can detergent residue left in the pump. If a damaged pressure washer pump is causing low pressure at the nozzle, replace the pump with the manufacturer-approved replacement part.
This basic procedure works for Craftsman, Briggs & Stratton, Snapper, Troybilt, Husqvarna and Generac pressure washers.
Disconnect the spark plug wire
Disconnect the spark plug wire from the spark plug.
Disconnect the hoses attached to the pump
Remove the inlet water hose from the pump, if attached.
Remove the nozzle hose from the pump.
Clamp the chemical injection tube if the tube has fluid in it. Pull the chemical injection tube off of the chemical injection inlet valve.
Clamp off the chemical injection hose.
Pull the chemical injection hose off of the valve.
Remove the pump
The pump is attached to the bottom of the pressure washer by 3 Allen-head bolts.
Loosen but don't remove the Allen-head mounting bolts that secure the pump to the engine.
With the pressure washer upright, support the bottom of the pump while removing the Allen-head mounting bolts from the pump.
Pull the pump off of the engine crankshaft or allow the pump to drop down and off of the crankshaft to remove the pump from the engine.
Loosen the pump mounting bolts.
Remove the pump.
Prepare the new pump for installation
Transfer the thermal relief valve from the old pump to the new one.
Use pipe thread sealing tape to seal the thermal relief valve connection.
Install the new pump
Rotate the notch in the pump drive connection to align the notch with the key on the engine crankshaft.
Slide the pump onto the engine crankshaft.
Rotate the pump to align the mounting holes.
Reinstall the Allen-head mounting bolts and tighten them securely.
Install the new pump.
Reconnect the hoses on the pump
Reconnect the chemical injection tube on the chemical injection inlet valve.
Remove the hose clamp from the chemical injection hose, if used.
Reconnect the nozzle hose connection and the inlet water hose connection on the pump.
Reconnect the chemical injection hose.
Reconnect the spark plug
Reattach the spark plug wire.
Test the new pump
Start the pressure washer and test the new pump.
The unloader valve recirculates water to protect the pump from damage. If the unloader valve is defective, replace it using the steps in this repair guide.
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.
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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