Install a high-pressure tip on the pressure washer.
Locate the nut located on the top of the unloader valve. Choose a wrench of the appropriate size, and remove the nut using a counterclockwise turning motion. Place the nut to the side. If the nut is stripped, you can use vice grips and a hammer to obtain proper leverage. The nut may need to be replaced in this case and can be obtained from a hardware store.
Turn the pressure adjusting knob in a counterclockwise direction until it is completely removed. Set the knot aside. This knob is usually manufactured from plastic.
Remove the washer and spring to expose the piston rod and locking nuts that hold the unloader valve in place.
Slide a wrench over the locking nuts so the two nuts are held firmly in the same position and cannot move independently of one another.
Replace the washer and spring.
Attach a pressure gauge assembly to the pressure hose. The assembly should be positioned between the pump and the hose so you can visualize the gauge while activating the washer and adjusting the components.
Turn on the water valve.
Press the trigger on the gun until all of the air is ejected from the hose and water is coming out.
Turn on the pressure washer.
Trigger the gun one time while observing the pressure gauge. Tighten the spring as needed. Continue triggering the gun and tightening the spring until the pressure increase ranges between 6 and 9 percent when the trigger is depressed. If this range cannot be achieved, tighten the locking nuts and repeat the procedure.
Press and release the trigger 20 times to break in the unloader. Recheck the pressure and repeat Step 11 as needed.
Replace the adjusting knob and nut.