2.2 Common Rail [1] Construction The functionof the rail is to distribute the high-pressure fuel pressurized by the supply pump to each cylinder injector. The rail pressure sensor, flow damper, and pressure limiter are mounted on the rail. A fuel injection pipe is attached to the flow damper to deliver high-pressure fuel to the injector. The pressure limiter piping is routed back to the fuel tank. Flow damper Pressure limiter Pail pressure sensor [2] Flow Damper The flow damper reduces pressure pulsation in the high-pressure pipe, thus delivering fuel to the injectors at a stable pressure.
Furthermore, in the event an ex- cessive flow of fuel, the flow damper shuts off the fuel passage, thus preventing the abnormal fuel flow. When abnormal amount of fuel flows the high-pres- sure is applied to the piston. As shown in the illustra- tion, this causes the piston and ball to move right, until the ball reaches the seat and closes the fuel passage. Q000092E Stopped During damping During abnormal flow such as excessive injection volume Piston Ball Seat [3] Pressure Limiter The function of the pressure limiter is to dispel abnormally high pressure by opening its valve to release pressure. The pressure limiter operates (opens the valve) when rail pressure reaches approximately 140MPa.
Then, when the pressure decreases to approximately 30MPa, the pressure limiter resumes (closes the valve) its function to maintain pressure. Q000093E Pc NOTE: Do not attempt to remove or to reinstall the flow damper, pressure limiter, or rail pressure sensor. Q000094E 9