The invention pertains to an aqueous solution of a sodium salt xNa+ yH+ of the chelating compound of formula I:wherein x=2. The barcode reading station includes a holster for a barcode reader, the barcode reader producing a scan volume, a barcode reading table for identifying a target location for barcode reading, and a mirror for deflecting the scan volume of the barcode reader towards the barcode reading table. An ECU switches the relief valve to the open state and operates the low-pressure fuel pump, if a predetermined stop condition for stopping the engine is satisfied.