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A diesel fuel injection system is the heart of a diesel engine. It consists of a fuel injection pump, high-pressure pipe, injection nozzle, feed pump, and fuel filter. This system pressures and injects fuel by forcing it into the air that has been compressed to high pressure. It serves to feed fuel, adjust its quantity, adjust injection timing, and atomize the fuel itself.

In this article, we'll explore the four types of diesel fuel injection systems. Read below to see what you need for your diesel engine.

Direct injection

This injection type makes use of a powerful, positive displacement fuel pump. It pumps the diesel fuel through injectors that are mounted in the cylinder. This system works well with a diesel engine as it produces huge amounts of fuel into the combustion chamber. Hence, the combustion process becomes faster, quieter, and more powerful.

One major facet of direct injection is the fuel pump. This pump forms and functions like a small four-stroke engine. However, it passes liquid diesel fuel instead of air and fuel. The pump has positive displacement, making the fuel pressure high yet stable. Such pressure is required to inject fuel against the compressive force of a rising piston.

Throttle Body Injection (TBI)

This injection type works like carburetion, which is where a lot of TBI units were patterned. Their difference lies in the fact that TBI employs a set of downward-facing injectors to shoot fuel into the engine under pressure. 

Modern diesel engines don’t often have TBI since there are already far better alternatives. Besides, it doesn't work well with turbocharging, which is one of its disadvantages.

Multipoint injection

This injection type is similar to those used in cars, and it employs a single or dual fuel pumps to provide fuel injectors. These injectors are mounted in the intake port of the engine. What happens is that the injectors spray fuel into the engine's intake valves through the intake port. 

As it is developed after the mechanical direct injection, the multipoint injection system is rarely used on most diesel types. Overall, it offers no real advantage for compression-ignition engines.

Common Rail Injection (CRI)

This injection type is both direct injection and multi-port injection rolled into one. It works like a multi-port injection, where it utilizes a common fuel rail to feed multiple fuel injectors. However, the difference lies in the fact these injectors are mounted inside of the direct injection. 

Given this combination, it gives you the control and flexibility to regulate the amount of fuel injected and the injection timing via a computer. Overall, the single, powerful fuel pump is the driving formula for CRI's ultimate success.

Conclusion

So these are the four types of diesel fuel injection systems—direct injection, throttle body injection, common rail injection, and multipoint injection. Each has its own features and functions, as well as pros and cons. No matter what type of fuel injection system you choose, be sure that it serves your diesel engine needs well.

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