Common rail injection system, also known as a high-pressure injection system, is a type of fuel injection system used in modern diesel engines. It works by pumping a large amount of fuel into the combustion chamber at high pressure through a common rail, which is a single, high-pressure rail that delivers fuel to the injectors. The high pressure allows for precise control of fuel injection, resulting in improved engine performance and fuel efficiency. Common rail injection systems have become increasingly popular in the automotive industry due to their high fuel efficiency and low emissions.