How to replace a pressure washer pump

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 gas pressure washer part.

This procedure shows Craftsman pressure washer pump replacement but the same basic process works for pump replacement on Briggs & Stratton, Snapper, Troybilt, Husqvarna and Generac pressure washers.

Instructions

1. Disconnect the spark plug wire

Disconnect the spark plug wire from the spark plug.

2. 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.

3. 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. 

4. 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.

5. 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.

6. 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.

7. Reconnect the spark plug

Reattach the spark plug wire.

8. Test the new pump

Start the pressure washer and test the new pump.