An external view of a typical pump,The main rotating components are the drive shaft ,distributor rotor , transfer pump blades, and governor components.
The drive shaft engages the distributor rotor in the hydraulic head. The drive end of the rotor incorporates two pumping plungers.The plungers are actuated toward each other simultaneously by an internal cam ring through rollers and shoes which are carried in slots at the drive end of the rotor. The number of cam lobes normally equals the number of engine cylinders. The transfer pump at the rear of the rotor is the postive displacement vane-type and is enclosed in the end cap. The end cap also houses the fuel inlet strainer and transfer pump pressure regulator. Transfer pump pressure is automatically compensated for viscosity effects due to both temperature changes and various fuel grades.

The distributor rotor incorporates two charging ports and a single axial bore with one
discharge port to serve all head outlets to the injection tubings. The hydraulic head contains
the bore in which the rotor revolves, the metering valve bore, the charging ports and the head
outlet fittings. The high pressure injection tubings leading to the nozzles are fastened to
these fittings. Distributor pumps contain their own mechanical governor capable of close speed
regulation. Both all-speed and min-max types are available. The centrifugal force of the weights
in their retainer is transmitted through a sleeve to the governor arm and through a linkage to
the metering valve. The metering valve can be closed to shut off fuel through the linkage by an
independently operated shut-off lever.