A fault diagnostic apparatus for evaporated fuel purging system

摘要

The fault diagnostic apparatus of the present invention detects a failure (a leak) of a fuel tank of an engine. In this invention, space about the fuel level in the fuel tank is connected to a canister. The canister contains an adsorbent to adsorb evaporated fuel in the tank to prevent the evaporated fuel from being released to the atmosphere. Valves are provided to the canister to keep the internal pressure of the canister within a predetermined range. A control circuit of the engine employs a pressure sensor to monitor the internal pressure of the fuel tank, and determines whether the fuel tank has failed by comparing the internal pressure of the fuel tank detected at the start of the engine with the internal pressure of the fuel tank detected within a predetermined period after the engine starts. <IMAGE>