Internal combustion engine comprising an electronic fuel injection control system for an internal combustion engine, said internal combustion engine being equipped with at least one fuel feeding line provided with a fuel tank , at least one throttle valve capable of regulating the air flow, at least one injector , at least one fuel pump (17; 18), at least one fuel return line comprising at least one solenoid valve , at least one first fuel return duct that connects said injector to said solenoid valve , at least one overpressure valve , at least one second return conduit adapted to connect said overpressure valve and said solenoid valve with said tank , wherein said fuel return line is provided with at least one calibration means , where said calibration means : - is sized and designed so as to simulate a specific fuel consumption of the said engine; - comprises narrowings or section shrinkages, holes; - allows at least verifying the state of said fuel pump (17; 18) and the related performance thereof; wherein said calibration means has geometries capable of simulating, with said solenoid valve substantially totally open, the consumption of the said engine at maximum speed, i.e., the fuel maximum operating flow rate (Qmax) required by said engine at maximum speed; and wherein said system comprises at least one fuel pressure sensor means and at least one control unit provided with at least one microcontroller , memory means and at least one processing and/or control software, where said system, by means of said calibration means and said control unit , performs a check test adapted to identify and define the values of the number of revolutions of said fuel pump necessary to obtain the fuel minimum (Pmin) and maximum (Pmax) pressure values, respectively, i.e. the pressure values capable of delivering the fuel minimum operating flow rate (Qmin) and the fuel maximum operating flow rate (Qmax) so as to meet the operating limit conditions of the said engine. - is sized and designed so as to simulate a specific fuel consumption of the said engine; - comprises narrowings or section shrinkages, holes; - allows at least verifying the state of said fuel pump (17; 18) and the related performance thereof; wherein said calibration means has geometries capable of simulating, with said solenoid valve substantially totally open, the consumption of the said engine at maximum speed, i.e., the fuel maximum operating flow rate (Qmax) required by said engine at maximum speed; and wherein said system comprises at least one fuel pressure sensor means and at least one control unit provided with at least one microcontroller , memory means and at least one processing and/or control software, where said system, by means of said calibration means and said control unit , performs a check test adapted to identify and define the values of the number of revolutions of said fuel pump necessary to obtain the fuel minimum (Pmin) and maximum (Pmax) pressure values, respectively, i.e. the pressure values capable of delivering the fuel minimum operating flow rate (Qmin) and the fuel maximum operating flow rate (Qmax) so as to meet the operating limit conditions of the said engine. <EOS>