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.