Method of controlling the fuel injection pressure of an internal combustion engine common rail injection system

There is described a control method for controlling the fuel injection pressure of a common rail injection system (2), the injection system (2) having a high-pressure pump (6) for supplying high-pressure fuel to the common rail (5), and for performing, at each engine cycle, a first and at least a second fuel delivery synchronously with respective fuel injections to the engine; a regulating device (9) for regulating the fuel pressure in the common rail (5); and an electronic control unit (4) supplying the regulating device (9) with a control signal (SCOM) to regulate the fuel pressure in the common rail (5). The control method provides a first value (DC1) of the duty cycle (DC) of the control signal (SCOM) as a function of a required pressure value (PR) and an actual pressure value (PE) in the common rail (5); and a second value (DC2) of the duty cycle (DC) of the control signal (SCOM) as a function of the first value (DC1) and a total correction coefficient (CCR); causing the duty cycle (DC) of the control signal (SCOM) to assume the first value (DC1) during the first fuel delivery; and causing the duty cycle (DC) of the control signal (SCOM) to assume the second value (DC2) during the second fuel delivery.