High pressure fuel pump

A high-pressure pump comprising:

• a main unit for pumping a transferred liquid;
• a secondary unit for pumping a working liquid, the secondary unit actuating the first unit and having at least one piston for compressing the working liquid;
• the piston equipped with an axial drilling for collecting leaks of working liquid between a reservoir and a working-liquid compression chamber;
• the compression chamber being delimited by a flexible diaphragm located in the main unit for pumping transferred liquid;
• the piston further including a valve for shutting off the axial drilling, the valve being housed in the drilling between two ends of the drilling in permanent communication with the reservoir and the compression chamber respectively, the valve opening when the pressure of the working liquid in the reservoir exceeds that of the working liquid in the compression chamber, and closing when the reverse occurs;
• the diaphragm separating the compression chamber from a variable-volume pumping chamber for the transferred liquid, wherein the diaphrapm is free from rigid connection to the piston, when the diaphragm is moveable between a first position in which the pumping chamber has maximum volume, toward which position this diaphragm is elastically returned by a diaphragm spring, even when there is no transferred liquid in the main unit, and a second position in which the pumping chamber has minimum volume;
• the stiffness of the diaphragm spring being chosen so that the diaphragm spring keeps the working liquid contained in the compression chamber at a raised pressure with respect to the working liquid contained in the reservoir for as long as the diaphragm has not reached the first position.