from the canister 73, is connected to an intake passage 77 of an engine 76. The canister 73 first adsorbs the vaporized fuel drawn in through the vapor line 72. The canister 73 collects fuel and discharges only the residual gas, from which fuel components (particularly hydrocarbon, HC) have pen extracted, into the atmosphere through a hole 78. The fuel collected in the canister 73 is purged into the intake passage 77 by way of the purge line 75 during operation of the engine 76. A purge control valve 79, provided in the purge line 75, adjust the flow rate of the fuel conveyed through the purge line 75 in accordance with the requirements of the engine 76.
In this typical treating device, damage or disconnection of the vaporapparatus includes a pressure sensor 88, which separately detects the interior pressure in the tank side of the vapor control valve 87 and the canister side of the vapor control valve 87. That is, a three-way valve 89, connected to the pressure sensor 88, including a port connected to the vapor line 83 at the side of the tank 81 and another port connected to the vapor line 83 at the side of the canister 82. The pressure sensor 88 selectively detects the tank pressure and canister pressure when the ECU 86 switches the side which the three-way valve 89 is connected to in accordance with its requirements. The ECU 86 separately tests the sealed state of the tank side and the sealed state of the canister side