The present invention relates to a method for determining whether there is leak present in a pressurized fuel system mounted on board of a vehicle when the vehicle is key-off. The method comprises the following steps:
- measuring temperature and pressure in the pressurized fuel system at predetermined time points;
- comparing temperature measurements with each other, so as to calculate a temperature differential between the highest temperature measurement and the lowest temperature measurement and
- comparing the temperature differential with a predetermined threshold for temperature differential.
If the temperature differential is less than the predetermined threshold for temperature differential, the method is then aborted aborting the method while, if the temperature differential is equal to or greater than the predetermined threshold for temperature differential, calculating a pressure differential between the pressure measurement measured at the same time point with the highest temperature measurement and the pressure measurement measured at the same time point with the lowest temperature measurement. In that case, the pressure differential is compared with a predetermined threshold for pressure differential, and the presence of a leak in the pressurized fuel system can be determined if the pressure differential is equal to or less than the predetermined threshold for pressure differential.
The invention allows a frequent enough determination of leak at reduced consumption and cost but with improved accuracy and which is capable of meeting the increasingly strict regulations of law.