The CP3 is driven by a gear off the front of the crankshaft, and then uses electronic solenoids to regulate the amount of fuel pressure delivered to the rail. In the past Cummins engines with the VE, P7100, and VP44 pumps they were called “smart” pumps. They controlled the timing and the amount of fuel delivered to each injector. The CP3 pump is a “dumb” pump. It simply pushes out as much fuel as it is told to and at what pressure it’s told to. Then the timing and duration of the injectors is controlled by the ECU sending an electrical signal to each injector.
In this diagram, you can see the flow of the high-pressure fuel circuit. Once through the metering unit, fuel makes its way to the suction valves (A). The suction valves are located at the top of the plungers (B) and allow fuel to enter each of the pump’s three cylinders. Finally, the high-pressure valves (C) send pressurized fuel out to the rail.