1. A method for operating a high-pressure accumulator fuel injection system for an internal combustion engine of a motor vehicle having an automatic stop/start function for deactivating and subsequently restarting the internal combustion engine independent of an intervention by the motor vehicle driver, in which fuel is fed to a high-pressure accumulator by a high-pressure pump, with at least one injector connected to the high-pressure accumulator for injecting fuel into at least one cylinder of the internal combustion engine, the method comprising: measuring a pressure of fuel in the high-pressure accumulator periodically during a stop phase of operation; correlating the measured pressure value to an actuation current value of an electrically activated pressure control valve which is open in a currentless state using a pressure/current characteristic curve; supplying a current to the pressure control valve at the actuation current value; and as the stop phase continues, adjusting the supplied current based on a pressure drop in the high-pressure accumulator and the pressure/current characteristic curve.
2. The method of claim 1 , comprising restricting reduction of the level of the electric current to avoid overshooting a minimum injection release pressure of the at least one injector.
3. The method of claim 1 , comprising, when the internal combustion engine is deactivated, (a) determining the pressure in the high-pressure accumulator and using said determined pressure as an input variable of a characteristic diagram in which a pressure reduction curve of the high-pressure accumulator fuel injector system plotted against the time is stored, (b) after expiry of a predetermined time period, identifying from the characteristic diagram a pressure value corresponding with the current time, (c) using the identified pressure value as an input variable of a characteristic diagram in which associated values of the actuation current are stored as a function of the pressure, and (d) repeating steps (b) and (c) at predetermined time intervals.
4. The method of claim 1 , further comprising determining the values of the electric current based at least on a determined temperature of the fuel.
5. A device for operating a high-pressure accumulator fuel injection system for an internal combustion engine of a motor vehicle having an automatic stop/start function for deactivating and subsequently restarting the internal combustion engine independent of intervention by the motor vehicle driver, in which fuel is fed to a high-pressure accumulator by a high-pressure pump, with at least one injector connected to the high-pressure accumulator for injecting fuel into at least one cylinder of the internal combustion engine, wherein the device is configured to: receive a measured value for a pressure of the fuel in the high-pressure accumulator periodically during a stop phase of operation; correlate the measured pressure value to an actuation current value of an electrically activated pressure control valve which is open in a currentless state using a pressure/current characteristic curve; supply current to the pressure control valve at the actuation current value, and as the stop phase continues, adjusting the supplied current based on a pressure drop in the high-pressure accumulator and the pressure/current characteristic curve.
6. The device of claim 5 , configured to restrict reduction of the level of the electric current to avoid overshooting a minimum injection release pressure of the at least one injector.
7. The device of claim 5 , configured to, when the internal combustion engine is deactivated, (a) determine the pressure in the high-pressure accumulator and using said determined pressure as an input variable of a characteristic diagram in which a pressure reduction curve of the high-pressure accumulator fuel injector system plotted against the time is stored, (b) after expiry of a predetermined time period, identify from the characteristic diagram a pressure value corresponding with the current time, (c) use the identified pressure value as an input variable of a characteristic diagram in which associated values of the actuation current are stored as a function of the pressure, and (d) repeat steps (b) and (c) at predetermined time intervals.
8. The device of claim 5 , configured to determine the values of the electric current based at least on a determined temperature of the fuel.
9. An internal combustion engine of a motor vehicle, comprising: at least one cylinder, a high-pressure accumulator fuel injection system having a high-pressure accumulator, a high-pressure pump configured to feed fuel to the high-pressure accumulator, and at least one injector connected for injecting fuel into the at least one cylinder, a control system for an automatic stop/start function for deactivating and subsequently restarting the internal combustion engine independent of intervention by the motor vehicle driver, and a pressure control device configured to: receive a measured value for a pressure of the fuel in the high-pressure accumulator periodically during a stop phase of operation; correlate the measured pressure value to an actuation current value of an electrically activated pressure control valve which is open in a currentless state using a pressure/current characteristic curve; supply current to the pressure control valve at the actuation current value, and as the stop phase continues, adjusting the supplied current based on a pressure drop in the high-pressure accumulator and the pressure/current characteristic curve.
10. The internal combustion engine of claim 9 , wherein the pressure control device is configured to restrict reduction of the level of the electric current to avoid overshooting a minimum injection release pressure of the at least one injector.
11. The internal combustion engine of claim 9 , wherein the pressure control device is configured to, when the internal combustion engine is deactivated, (a) determine the pressure in the high-pressure accumulator and using said determined pressure as an input variable of a characteristic diagram in which a pressure reduction curve of the high-pressure accumulator fuel injector system plotted against the time is stored, (b) after expiry of a predetermined time period, identify from the characteristic diagram a pressure value corresponding with the current time, (c) use the identified pressure value as an input variable of a characteristic diagram in which associated values of the actuation current are stored as a function of the pressure, and (d) repeat steps (b) and (c) at predetermined time intervals.
12. The internal combustion engine of claim 9 , wherein the pressure control device is configured to determine the values of the electric current based at least on a determined temperature of the fuel.
