METHOD FOR TESTING THE SEALING TIGHTNESS OF A FUEL TANK SYSTEM OF AN INTERNAL COMBUSTION ENGINE

The invention relates to a method for testing the sealing tightness of a fuel tank system of an internal combustion engine, wherein the fuel tank system comprises: a fuel tank (10); a fuel vapor filter (14), which is connected in a fluid-conducting manner to an environment opening (62); a venting line (12), which leads from the fuel tank (10) to the fuel vapor filter (14), a purge air line (16), which leads from the fuel vapor filter (14) to a fresh gas tract (18) of the internal combustion engine; a compressor (64) integrated into the purge air line (16); and a shutoff valve (60), which is integrated into the purge air line (16) and which is arranged between an opening (50) of the purge air line (16) into the fresh gas tract (18) and the compressor (64), is characterized in that sufficient sealing tightness and insufficient sealing tightness are distinguished by a comparison of at least one value or value curve of a parameter that corresponds to an operating parameter of the compressor (64) or to the pressure in at least one section of the purge air line (16) that should be tested, said value or value curve being determined in a defined operating state of the fuel tank system, with an associated set point value or set point value range, which represents said operating state and which corresponds to sufficient sealing tightness.