Abstract: A theft-prevention system for a motor vehicle wherein at least one cylinder lock having a closing cylinder and a switching mechanism that is relatively translatable with respect to the closing cylinder for actuating and deactuating the cylinder lock is engageable by a first key which is able to actuate and deactuate only the cylinder lock, and a second key which is engageable with the cylinder lock for actuating and deactuating both the closing cylinder and at least one auxiliary system for deterring the theft of the vehicle. Actuation of the auxiliary system by the second key engages a locking mechanism preventing operation of the cylinder lock.

Abstract: A valving mechanism or closing apparatus for ventilation lines of fuel tanks in motor vehicles is provided which comprises a housing and closing elements contained in the housing, which closing elements are movable in accordance with the vehicle position. The closing elements are formed as movable members, one above the other, with the lower member being a mass body lying against a guide wall of the housing and being freely movable to a certain extent, while the upper element acts to close an exit opening of the housing, thereby closing the ventilation line. The lower mass body element may be conically configured to match the conically configured guide wall of the housing, or the mass body may be a ball shaped body which moves along the guide wall of the housing. The upper element may also be a floating body such that an overflow of gasoline into the housing causes the floating body to close the exit opening, thereby preventing discharge of fuel out of the ventilation line.