Patent ID: 7963150

Claim:
A method of testing for a leak in a fuel tank system of a motor vehicle, comprising: cutting off a fuel tank during an overrun by at least one cutoff device and acquiring a pressure that builds up in the fuel tank within a specifiable time interval; and when a specifiable maximum pressure or a specifiable vacuum threshold is unrealized, opening the at least one cutoff device and closing the at least cutoff device again after a specifiable time period, producing and acquiring a vacuum in a subsequent vacuum phase, determining and evaluating a first parameter that characterizes leak tightness from the vacuum achieved within a specifiable time period and an achieved overpressure, when the specifiable maximum pressure is realized, determining a second parameter characterizing leak tightness from the overpressure and a specifiable overpressure threshold and comparing the second parameter with a specifiable reference value, upon the second parameter being found less than the reference value, suggesting a leak-proof fuel tank system; and when the determined second parameter is greater than the specifiable reference value, opening the cutoff device, producing and acquiring a vacuum in the fuel tank in a subsequent vacuum phase, wherein a leak-proof fuel tank system is suggested when a specifiable vacuum threshold is achieved and the test for a leak is concluded, and whereby the test for a leak is then concluded if the vacuum threshold is not achieved within a specifiable time period, and thereby a parameter characterizing leak tightness is evaluated.