and the atmospheric temperature and hence the amount of remaining fuel and the atmospheric temperature do not produce effects thus it is not necessary to make a correction based on these factors further since the pump 14 stops increasing the pressure at the specified pressure p 0 it is not necessary to use the pump 14 having a high discharge capacity still further this shortens the operation time of the pump 14 and reduces load applied to the pump 14 and hence elongates the life of the pump 14 thus this reduces power consumption and saves energy in contrast to the first embodiment in which it is determined whether the leak is much or little by the length of time required for the pressure p to decrease from the specified pressure p 0 to the specified pressure p 1 in this embodiment it is determined whether the leak is much or little by the determination as to which of the time when the lapsed time t 2 becomes larger than the determination base time t 1 u00d7 2 and the time when the pressure p becomes lower than the specified pressure p 1 comes earlier so that after the determination base time t.