Patent ID: 6460518
Filing Date: 2002-10-08
Classification: F02M,G01M

Abstract:
A method for checking the tightness of a tank system including the tightness of a tank-venting system of a vehicle, the method comprising the steps of:introducing an overpressure or an underpressure relative to the atmospheric pressure into the tank system utilizing a pressure source and detecting the time-dependent trace of at least one operating characteristic variable of the pressure source when introducing the overpressure/underpressure up to reaching a first time point or a first pressure level; comparing said time-dependent trace to a time-dependent trace of the operating characteristic value up to this time point or up to this pressure level (expected diagnostic trace), the time-dependent trace being expected in the case of a tight tank system; drawing a conclusion as to non-tightness when the detected time-dependent trace deviates from the expected diagnostic trace by at least a pregiven value; when a deviation is determined, further increasing the overpressure/underpressure in the tank-venting system up to reaching a second time point or a second pressure level; continuing to detect the operating characteristic variable of the pressure source and comparing said operating characteristic variable to an expected further time-dependent trace of the operating variable in the case of a tight system (further diagnostic trace); and, outputting a fault announcement only when the detected time-dependent trace during the introduction of the further overpressure/underpressure deviates from the further diagnostic trace.