Method and device for operating an internal combustion engine comprising a high-pressure fuel injection system

A method for operating an internal combustion engine comprising a high-pressure fuel injection system (HD_SYS) for an internal combustion engine of a motor vehicle, said system having an automatic stop/start function, by which the internal combustion engine can be switched off independently of an intervention by the motor vehicle operator and then restarted, and in which a high-pressure fuel pump is used to pump fuel to a high-pressure reservoir to which at least one high-pressure fuel injector is connected in order to inject fuel into the at least one cylinder of the internal combustion engine, and the fuel pressure can be adjusted on the high-pressure side using an electrically actuated pressure reduction valve (PDV), the method comprising:

• when the internal combustion engine is stopped, opening the pressure reduction valve (PDV) until a specified value of an injection release pressure is established which ensures a restart after a stop phase within a stop/start cycle, and the pressure reduction valve (PDV) is subsequently closed,
• determining whether a restart of the internal combustion engine takes place within a specified time period,
• injecting fuel using the value of the release pressure if a restart occurs within the specified time period,
• otherwise, opening the pressure reduction valve (PDV) after the specified time period expires until the pressure of the fuel in the high-pressure reservoir has decreased to a value of the ambient pressure of the motor vehicle.