Common Rail Diesel Engine: Working Principle, Pros and Cons

Last Updated on May 11, 2019 by themechanic

Diesel engines have evolved over the last 50 years. The older diesel engines consisted of a fuel injection system that was like the one found in gasoline engines. This fuel injection system included pump nozzles and fuel injectors. At low pressure, the fuel injectors received fuel from the pump nozzles and then sprayed fuel into the engine.

As effective as this may have been for power generation purposes, it was not too environmentally friendly. In fact, the fuel injection system in diesel engines was responsible for producing a high level of carbon emissions. This didn’t really matter to people, at first, but then things changed over time. Our society became increasingly aware of the dangers that carbon emissions imposed on the environment.

As a result, lawmakers required automakers to do something to reduce the high levels of carbon emissions coming from their vehicles. In response, the common rail diesel engine was invented. This is the engine now found in most trucks that are traveling on the streets and highways these days. The common rail diesel engine can lower carbon emissions because of its several solenoid valves and high-pressure rail system. The rail basically sends fuel into each valve. From there, the fuel enters the internal combustion chamber of the engine.

At this point, you’re probably ready to go out and purchase a new truck with a common rail diesel engine in it. But wait, you may want to review the pros and cons of the common rail diesel engine first. For some people, they prefer the classic diesel engine over the new one, despite the common rail being environmentally friendly.


The biggest advantage of the common rail diesel engine is it generates fewer carbon emissions. In some jurisdictions, you’ll actually be required to drive a vehicle with a common rail diesel engine if you want to comply with the local carbon emission laws. Otherwise, your diesel vehicle will never pass its emissions test if it has a fuel injection system in it.

We should all care about the environment, so why not choose the diesel engine which serves it better? If you need another incentive to go with the common rail diesel engine, how about less black smoke? Remember the old days when diesel engines produced all that black smoke? The common rail diesel engine has greatly reduced the amount of black smoke which comes out of the tailpipe. This makes it more attractive and less irritating to the drivers around you.

And if power is what you care about, then you’ll definitely want the common rail diesel engine because it is more powerful than the classic diesel engine. In fact, studies show the common rail is 25% more powerful than the fuel injection model. This means your engine will perform better and give you more miles per gallon. As for your driving experience, you won’t hear a lot of annoying engine noises when you step on the accelerator pedal. Even the intensity of the vibrations is reduced.


So, what could the disadvantages of the common rail diesel engine be? There aren’t too many disadvantages other than the higher cost. Like anything else, you need to pay more to get better quality. That is why vehicles with common rail diesel engines cost more than vehicles with fuel injection diesel engines. But if you’re in a position where you need to comply with local emissions regulations, then you won’t have a choice. Other than that, wouldn’t you want to pay more to get a better performing engine?

The other big disadvantage is the maintenance requirements. Common rail diesel engines frequently need maintenance and repair work done on them. Because of this, it ends up costing you even more money.

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Overall, it is a matter of your budget and the laws of your local area. If you’re on a low budget and there are no carbon rules in your area, then choose the classic fuel injection diesel engine. But if you need to lower emissions and get a higher performance engine, then choose the common rail.

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