The high pressure fuel pump is an interface located between the low pressure and the high pressure stages. Under all operating conditions, it is responsible for providing adequate high pressure fuel throughout the vehicle's complete service life. This also includes the provision of extra as needed for rapid starting and for rapid build-up of pressure in the rail. The high pressure pump continually generates the system pressure as needed in the high-pressure accumulator (common rail). Therefore, this means that in contrast to conventional systems, the fuel does not have to be especially compressed for each individual injection process.

A: Fuel Feed Line (From fuel tank via fuel filter) [Low pressure fuel]

B: Fuel Feed Line (To common rail) [High pressure fuel]

C: Fuel return (To fuel tank) [Low pressure fuel]