Pressure regulator for a high-pressure rail of a system for injecting fuel into an internal combustion engine, comprising a solenoid valve body , which accommodates a solenoid , which controls the needle that closes the valve seat , which is connected to the high-pressure inlet and opens into a discharge chamber , which communicates through outlet apertures with the liquid return circuit , - wherein the rear side of the solenoid valve body accommodates the coil , which controls the opening of the rotor , which is fixedly connected to the needle and is subject to a closing return spring , - wherein the front side of the solenoid valve body , in the axis (XX) of the needle , comprises the discharge chamber , which surrounds the needle and extends through a cavity accommodating an inlet valve body , passing axially through which is the bore , which opens into the valve seat , - wherein the discharge chamber , through which the needle axially passes, and the outlet apertures , which are connected to the liquid return circuit, open transversally into the wall in the discharge chamber below the upper part of the chamber, wherein the regulator is characterized in that above the surface of the valve body , which forms the base of the discharge chamber and has the valve seat at its center, said regulator comprises an annular enlargement of the discharge chamber below the outlet apertures in the extension of the conical surface which constitutes the valve seat and forms an annular dead volume , wherein the dead volume has the following dimensional features: its diameter D1 (D11, D12) is greater than the diameter D2 of the discharge chamber, its axial length (L1) is smaller than or equal to the axial length of the discharge chamber between the upper surface of the valve body and the apertures , which communicate with the liquid return circuit, its dead volume is distinctly separated from the discharge chamber. - wherein the rear side of the solenoid valve body accommodates the coil , which controls the opening of the rotor , which is fixedly connected to the needle and is subject to a closing return spring , - wherein the front side of the solenoid valve body , in the axis (XX) of the needle , comprises the discharge chamber , which surrounds the needle and extends through a cavity accommodating an inlet valve body , passing axially through which is the bore , which opens into the valve seat , - wherein the discharge chamber , through which the needle axially passes, and the outlet apertures , which are connected to the liquid return circuit, open transversally into the wall in the discharge chamber below the upper part of the chamber, wherein the regulator is characterized in that above the surface of the valve body , which forms the base of the discharge chamber and has the valve seat at its center, said regulator comprises an annular enlargement of the discharge chamber below the outlet apertures in the extension of the conical surface which constitutes the valve seat and forms an annular dead volume , wherein the dead volume has the following dimensional features: its diameter D1 (D11, D12) is greater than the diameter D2 of the discharge chamber, its axial length (L1) is smaller than or equal to the axial length of the discharge chamber between the upper surface of the valve body and the apertures , which communicate with the liquid return circuit, its dead volume is distinctly separated from the discharge chamber. its diameter D1 (D11, D12) is greater than the diameter D2 of the discharge chamber, its axial length (L1) is smaller than or equal to the axial length of the discharge chamber between the upper surface of the valve body and the apertures , which communicate with the liquid return circuit, its dead volume is distinctly separated from the discharge chamber. <EOS>