A pressure-changing device of a leak check system for a fuel vapor treatment system has a pressure chamber formed in a peripheral space of a communicating path connecting a pump with an electromagnetic valve, the pressure chamber being deviated from flow delivered by the pump. Engine parameters that are retrieved through the interface during driving experience are uploaded to the database using the communication device. A temperature of each of the racks is determined based on i) a rate R at which the chilled air at a temperature Tc is introduced to each of the racks and ii) a rate R at which warm air from each of the racks at a temperature T is returned to the cooling system. The paused flow sends a request for permission to resume execution to a sync servlet.