The powder pump can be referred to as an injector or venturi pump. There is normally one pump for each gun which delivers powder from the feed hopper to the spay gun in a consistent and uniform flow. Pumps use the venturi principle in which air is passed over the venturi throat (a smaller constricted cylindrical section) and powder is drawn up though a pick-up tube into the pump where it is then passed on to the spay gun.
Powder pump parts are exposed to high-velocity powder streams, and therefore are prone to wear and impact fusion, especially the venturi throat. It is important to continually check this part for wear. When the venturi throat wears, it opens in diameter, allowing air to rush through creating inconsistent powder flow and increased impact fusion.
To prevent inconsistent powder flow and impact fusion, check, clean, and replace tubes, hoses, pumps, and nozzles on a regular basis.