Disconnect the spark plug wire from the spark plug installed on the Troy-Bilt engine. Tip the pressure washer on its back using the handle.
Pull off the chemical hose from the pump nozzle, which is on the right side as you view the pump from underneath the pressure washer.
Use a nut driver to unscrew and remove the three mounting bolts in the flanges on the pump. The flanges are arranged in a triangular pattern. Each bolt connects through a flange with a nut. Pull the pump off the engine shaft from below.
Slide the new pump in position on the engine shaft. The pump is pre-lubricated by the manufacturer and needs no other additional preparation.
Secure the pump with the three bolts and nuts, tightening each with the nut driver.
Slide the chemical hose onto the nozzle of the new pump.
Set the pressure washer upright and reconnect the spark plug wire when you are ready to use the equipment.