Abstract: A method for operating an internal combustion engine, in whose exhaust gas system an exhaust gas treatment device is positioned, a reagent, which is possibly mixed with compressed air, being introduced into the exhaust gas system upstream from the exhaust gas treatment device, and a device for performing the method. The reagent is brought to a predefined reagent setpoint pressure using a reagent pump and subsequently metered using a reagent dosing valve. The reagent pressure existing upstream from the reagent dosing valve is detected. In the framework of a diagnosis, a time curve of the reagent setpoint pressure is predefined. The reagent pressure detected during the diagnosis is compared to at least one predefined threshold value. If the threshold value is exceeded, an error signal is provided. The corresponding diagnosis of a compressed air path may be provided alternatively or additionally to the diagnosis of the reagent path.

Abstract: A method for operating an internal combustion engine, in whose exhaust gas system an exhaust gas treatment device is positioned, a reagent, which is possibly mixed with compressed air, being introduced into the exhaust gas system upstream from the exhaust gas treatment device, and a device for performing the method. The reagent is brought to a predefined reagent setpoint pressure using a reagent pump and subsequently metered using a reagent dosing valve. The reagent pressure existing upstream from the reagent dosing valve is detected. In the framework of a diagnosis, a time curve of the reagent setpoint pressure is predefined. The reagent pressure detected during the diagnosis is compared to at least one predefined threshold value. If the threshold value is exceeded, an error signal is provided. The corresponding diagnosis of a compressed air path may be provided alternatively or additionally to the diagnosis of the reagent path.

Abstract: A pressure control valve for installation in a supply line between a pump work chamber of a fuel injection pump and an injection point in the engine to be supplied. A valve body that has a first valve seat and an axial through conduit in which a pressure control valve closing member is guided. The pressure control valve closing member opens toward the injection point counter to the force of a first valve spring and has a sealing face that cooperates with the first valve seat, as well as with an axial through bore in the pressure control valve closing member. The bore can be closed by a back-flow valve that opens in the direction of the pump work chamber and has a second valve spring. For an optimal, unthrottled fuel flow through the pressure control valve, fuel conduits are respectively formed between the radially outer circumference faces of the first and second valve springs and the housing walls that encompass them, through which conduit the fuel flows in an unthrottled fashion.