Straighten the inlet hose and make sure the water faucet is fully on if the pump fails to produce pressure and exhibits low water volume. Change out the spray tip by pulling back on the quick-connect ring and pulling the spray tip off. Insert another tip. The black one is used to apply detergent, and the green and red ones are high-pressure tips.
Check and clean the inlet screen. Examine the screen on the pump's water inlet and look for clogs. Scrape any debris off with your fingernail.
Insert the detergent siphoning tube into the detergent if the detergent doesn't mix with the water and spray. Then unstick the check ball -- it can become gummed up with detergent -- by turning the engine and the water supply off. Press the red button pointing the spray in a safe direction to relieve pressure. Remove the detergent siphoning hose from the barbed fitting on the pump and, using an Allen wrench, poke the fitting until you reach the ball and feel it move.
If the engine won't start, or starts and then runs poorly, clean the air filter: Remove the screw on the top of the filter housing. Then remove the assembly, making sure debris doesn't fall into the motor. Clean all of the filter parts in a detergent-and-water mix, squeeze the filter and let it dry, and add a drop of oil to the foam. Squeeze the foam in a clean rag to remove excess oil before replacing the filter in the filter housing and securing the top with the retaining screw.