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Why are all diesel cars today common rail?

Model: (Various brands) Various
Part: Fuel injectors

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Why are today's cars all common rail and no one uses the pump-injector system anymore? In the first case, a pump generates high pressure that is sent to the rail from which all injectors draw the same pressure. An ECU decides when to open each individual injector.

In contrast, the pump-injector sends directly to the cylinder head, the engine turns the camshaft, compressing the individual pump for each injector, controlled by a single ECU. The system is very efficient, but it is also very expensive. It was a Volkswagen patent, developed solely for itself (while Fiat's common rail was sold to everyone except the VAG group), so it could not amortise the cost, and in the long run, it was abandoned.


Updated on 18 July 2026 by ScegliAuto


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