A high pressure fluid jetting system generally includes a fluid cylinder pump, a drive assembly, a pressurized liquid supply and an applicator gun. The drive assembly includes a diesel engine or electric powered motor which drives a rotatable drive shaft. The drive shaft drives a triple plunger which are reciprocally driven. A valve seat assembly and a cylindrical cartridge seal assembly define a cartridge which contains a reciprocating plunger shaft. The primary high wear parts are located therein. The cartridge is retained within the manifold cartridge opening yet is readily accessible by removal of the manifold. The pump output is primarily determined by the diameter of the plunger the length of the stroke, the number of cylinders, and the speed of the pump. A specific cartridge allows replacement of all the components which interface with a plunger shaft of a predetermined diameter such that a change in pump output or repair is readily achieved by straightforward cartridge replacement.