A method of predicting a cylinder pressure of a diesel engine by a pressure predicting device may include predicting a pilot injection combustion pressure by pilot injection; predicting main combustion duration of main injection; and predicting a main injection combustion pressure after the main injection by using the pilot injection combustion pressure and the main combustion duration.

A method of predicting a cylinder pressure of a diesel engine by a pressure predicting device may include predicting a pilot injection combustion pressure by pilot injection; predicting main combustion duration of main injection; and predicting a main injection combustion pressure after the main injection by using the pilot injection combustion pressure and the main combustion duration.

In a fuel system of an internal combustion engine, fuel is delivered by a high-pressure pump into a fuel rail. The quantity of the delivered fuel is influenced by a quantity control valve (30) actuated by an electromagnetic actuating device. A limit-value retaining current is ascertained, at which the quantity control valve still remains in its closed state or is just opening.