The figure shows common rail fuel injection system, in this system the pressure
required to inject the fuel is developed in a pump. Fuel at high pressure is
to a common rail by the high pressure fuel pump. A spring loaded by one word
pass valve maintains constant pressure on common rail and returns the excess
fuel. The pressure of common rail can be adjusted by adjustment of spring
tension on the bypass valve.
In common rail the fuel is distributed to a individual injector by different fuel
injector. Each furl injector contains a needle valve reached against the valve
seat by a spring. The valve is operated by cam, follower aand push rod.