The circular charging passage in the head of the injection pump has eight ports that align in pairs with the two ports of the rotor pumping chamber. Metered fuel under transfer pump pressure travels through the charging passage and enters the rotor, pushing two pumping plungers outward as it fills the chamber (refer to Figures 7-35 and 7-36). Two accumulators help maintain a consistent pressure in the charging passage.
Each pumping plunger contacts a shoe/roller assembly. The two shoe/roller assemblies contact the inner surface of a cam ring, which has eight lobes and valleys. During the charging of the pumping chamber, the valleys of the cam ring allow the pumping plungers and shoe/roller assemblies to move outward at a distance controlled by how much fuel fills the pumping chamber.
As the injection pump rotor continues its rotation, the two ports of the pumping chamber are blocked from the charging passage (refer to Figures 7-37 and 7-38). At the same time, two of the cam ring lobes push the shoe/ roller assemblies and pumping plungers inward, increasing fuel pressure in the pumping chamber to an amount approximately 100 times greater than the transfer pump pressure.
When the fuel pressure in the pumping chamber rises, a delivery valve is pushed against spring force. The fuel then moves past the delivery valve to a discharge port of the rotor. When a port in the head connecting to the injection line and nozzle for a particular cylinder aligns with the rotor discharge port, fuel under a pressure wave exits the injection pump.
The process of pressurizing and distributing fuel occurs eight times in one revolution of the injection pump drive shaft and rotor.
