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Mechanical Injection with Mechanical Timing
In the earlier models of the Cummins B Series Engine, it was almost entirely mechanical including its fuel system. The fuel pump used in these engines was the P7100 injection pump, this pump is driven off the camshaft gear and drives it own internal camshaft to inject fuel to the individual injectors. This pump itself was one of the most popular options for fueling for the B Series Engines because of this simplistic design and how reliable it was. The P7100 injection pump also allows for large amounts of fuel to be delivered into the system with simple tweaking to the system to allow for larger injection events.

Mechanical Injection with Electronic Timing
In the later models of B Series Engine, the fuel system was switched from mechanical injection and timing to mechanical injection with electronic timing. This was all thanks to Bosch’s new VP44 injection pump. The VP44 injection pump is driven at half the camshaft speed and produces fuel pressure at about 4,500 psi to pop the vertically centered injectors in the engine. These injection pumps need to have constant fuel pressure behind them of at least 10psi at all times to maintain the priming of the system. If you run these pumps dry it can cause your pump to fail quickly. The VP44 injection pumps were the first pumps placed in the Cummins engine to have an FPCM. FPCM stands for the fuel pressure control module, and this is responsible for maintaining and controlling the fuel pressure of the system. However, even though this new technology to control fuel pressure was convenient, it had a major downfall. The problem was them was that they were unable to be serviced without replacing the entire fuel pump. Another important piece of the puzzle that is responsible for the longevity and functionality of the VP44 was the fuel transfer pump mounted on the side of the block next to the ECM. This electronically driven vane pump is what supplies that minimum of 10psi to the injection pump so it maintains constant fuel pressure as well, as cools itself, and lubricates itself.

Mechanical Injection with Electronic Timing and Common Rail Pressurization
The most recent method of fuel injection that is still in use today is called common rail injection. Common rain injection is a completely revolutionary design to fuel injection since a fuel pump is now used to pressurize a rail and then from there sends the fuel to each injector. A major benefit of switching over to this fueling system was how it allowed for much less leakage into the cylinders pre and post ignition. This is all possible since this fuel system operated upwards of 2600 bar so they are able to set spring tension higher in each injector to allow for more precise fuel injection and timing. Another benefit of using common rial injection and having one rail pressurized compared to pressurizing each individual injector is that it is more reliable since it allows for more consistent fuel delivery to each injector.