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How the High-Pressure Pump Works in the Common Rail System

Model: (Various brands) Various
Part: Pump

Video tutorial

The high-pressure pump (HPFP = High Pressure Fuel Pump) is the beating heart of the injector. It receives low-pressure diesel from the feed pump and compresses it to extremely high pressures (up to 2,500 bar), sending it to the common rail, the accumulator pipe that distributes fuel to all injectors.

The already filtered and low-pressure pressurised diesel enters the pump; a piston retracts, creating a vacuum that opens an inlet valve, and the piston chamber fills with diesel. During the compression phase, the camshaft pushes the piston forward, the pressure in the chamber increases instantly, closing the inlet valve; once the pressure in the rail is exceeded, a non-return valve opens and the hyper-compressed diesel is pushed towards the common rail.

The critical component is the pressure regulator (PCV), which has a fundamental function as it is mechanically connected to the crankshaft, requiring constant pressure in the rail at all engine speeds. The pressure regulator bypasses excess diesel back to the return line to maintain the required value under all conditions.


Posted on 4 August 2026 by ScegliAuto


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