The DB2 is an opposed-plunger, inlet-metering, distributor-type diesel injection pump. It was designed for low-cost production and simplicity. A typical DB2 has approximately 100 components and only four main rotating members. There are no spring-loaded components, none are lap-fitted in manufacture, and there are no ball bearings or gears. The pump has a single pumping chamber in which two opposed plungers are actuated by an internal cam ring.

The shape of the hydraulic head determines the distribution of fuel between cylinders, and because fuel flow can be preset, lengthy periods on the fuel pump test bench are eliminated.

Fuel is drawn from the fuel tank by a mechanical lift pump that is completely independent of the DB2 injection pump, and passes through filters and into the injection pump inlet. From there, fuel flows past the inlet filter screen to the vane-operated transfer pump located in the DB2 pump end cap. The vane-type transfer pump consists of a stationary liner and spring-loaded blades carried in slots at the rear of the transfer pump rotor Dlla138s1191. As the blades rotate in the liner, they move outward and the volume increases until the leading blade passes out of registry through the inlet slot. The fuel between the blades is carried to the bottom of the transfer pump liner and enters the outlet groove. As a result, pressurized fuel is delivered through the pump into a channel to the hydraulic head passage.

Fuel delivered to the head passage by transfer pump pressure splits in several directions. A portion of the fuel goes to the pressure side of the pressure regulator delivery valve, while the remainder enters a circular passage in the head from which radial passages lead to the vent wire assembly and then to the governor housing and housing pressure regulator.

The pressure regulator assembly in the transfer pump regulates fuel volume based on changes in pump speed-pressure increases with pump speed.

The vent wire assembly is located behind the metering valve bore, and is made of a J-shaped wire retained in a hollow screw. The wire is free to vibrate and restrict excessive return oil and undue pressure loss. Fuel entering from the vent fills the housing, lubricates the internal components, and cools and carries away any small air bubbles through the return oil line.