Too much liquid in the tank. The sprayer has raised fill markings on the side of the tank – only fill to the max fill line. This will allow enough room in the tank for the air/pressure needed to allow the sprayer to function properly.
Inspect pump piston o-ring. If you are having a hard time pumping the sprayer, you could have a damaged piston o-ring. Again, have the pump removed from the tank. You will be separating the pump piston from the pump barrel. First pull the pump handle up until it cannot go any further. Then use a flat screwdriver to push the tabs in on both sides of the pump cylinder and pry up. At the end of the plastic piston/rod, there will be a black o-ring. Periodically this o-ring needs to be lubricated with a heavy coating of petroleum jelly to ensure a nice tight seal in the pump barrel – delivering as much air as possible per stroke. If you find this o-ring seal to be worn, damaged, or swollen, it will need to be replaced by ordering a pump service kit.*
