Abstract: There is described a method of diagnosing leakage in a common-rail injection system of an internal combustion engine having a number of cylinders; the injection system having a number of injectors, each supplying high-pressure fuel to a respective cylinder of the engine, and a fuel supply circuit supplying fuel to the injectors. The diagnosis method includes the steps of determining the contribution of each cylinder to the angular acceleration of the engine; determining, for each cylinder, an unbalance index indicating the unbalance of the angular acceleration contribution of the cylinder with respect to the angular acceleration contributions of the other cylinders; reducing, upon detection of a fault in the injection system, the amount of fuel injected into each cylinder; and distinguishing, for each injector, between a jammed-open injector condition and a fault condition in the fuel supply circuit, on the basis of the variation in the unbalance index of the respective cylinder following the fuel reduction.

Abstract: A method of assessing operation of a common-rail injection system of an internal combustion engine; the injection system having a number of injectors, a high-pressure circuit supplying high-pressure fuel to the injectors, and a low-pressure circuit supplying fuel to the high-pressure circuit; and the method including the steps of hydraulically isolating the high-pressure circuit from the low-pressure circuit and the engine; and assessing operation of the injection system as a function of the fuel pressure drop in the high-pressure circuit.

Abstract: There is described a method of diagnosing leakage in a common-rail injection system of an internal combustion engine having a number of cylinders; the injection system having a number of injectors, each supplying high-pressure fuel to a respective cylinder of the engine, and a fuel supply circuit supplying fuel to the injectors. The diagnosis method includes the steps of determining the contribution of each cylinder to the angular acceleration of the engine; determining, for each cylinder, an unbalance index indicating the unbalance of the angular acceleration contribution of the cylinder with respect to the angular acceleration contributions of the other cylinders; reducing, upon detection of a fault in the injection system, the amount of fuel injected into each cylinder; and distinguishing, for each injector, between a jammed-open injector condition and a fault condition in the fuel supply circuit, on the basis of the variation in the unbalance index of the respective cylinder following the fuel reduction.

Abstract: A method of assessing operation of a common-rail injection system of an internal combustion engine; the injection system having a number of injectors, a high-pressure circuit supplying high-pressure fuel to the injectors, and a low-pressure circuit supplying fuel to the high-pressure circuit; and the method including the steps of hydraulically isolating the high-pressure circuit from the low-pressure circuit and the engine; and assessing operation of the injection system as a function of the fuel pressure drop in the high-pressure circuit.

Abstract: The diagnostic method includes the steps of: generating a pressure signal related to the fuel pressure of an injection system of an engine; comparing the pressure signal with a reference pressure value; determining a fuel leakage condition of the injection system when the pressure signal is less than the reference pressure value; reducing the quantity of fuel injected into the cylinders of the engine in the presence of the leakage condition; calculating a share value contributed by each cylinder to the work torque value generated by the engine; comparing each share value with a respective reference share value; determining a jammed-open injector condition when at least one of the share values is greater than the respective reference share value; and determining a supply circuit failure condition when the share values are all less than the respective reference share values.

Abstract: An electronic system (1) for controlling the injection pressure of a fuel injection system (4) wherein a pump (8) supplies fuel at high pressure to a rail (17) presenting a number of outlets (19a, 19b, 19c, 19d) communicating with respective injectors (21a, 21b, 21c, 21d). The injection system (4) presents a pressure regulator (24) interposed between the outlet (8a) of the pump (8) and the inlet (17a) of the rail (17), and controlled by a drive signal (U(z)) generated by a regulator circuit (50); the regulator circuit (50) is supplied with a digital error signal (Err(z)) representing the difference between a signal (Pmis(z)) generated by a pressure sensor (38) in the rail, and a signal (Prif(z)) representing an optimum reference pressure; and the regulator circuit (50) presents a transfer function R(z) of type (1), where "a", Kc are calculated numeric coefficients, and z is a digital variable.