apparatus and method for on - board lubrication of a paint pumping piston including a reservoir for lubricant and a lubricant dispensing mechanism for delivering a predetermined repeatable amount of lubricant upon manual actuation of the lubricant dispensing mechanism . in one embodiment , a section of tubing acts as the reservoir , and in another embodiment , the reservoir is formed by a transparent or translucent chamber located adjacent an aperture in a pump housing to enable visual inspection of the level of lubricant in the reservoir . a lubricant delivery piston is actuated by an extension thereof projecting through an aperture in the housing , and a lubricant discharge nozzle is located adjacent the paint pumping piston proximate a bushing supporting the paint pumping piston . a breather valve prevents a vacuum in the reservoir as the lubricant is dispensed .