Abstract: A plug-in hybrid vehicle is driven by one or more electric motors powered by a battery system with supplemental electric power provided by a gasoline engine powered generator. A canister, connected by a fuel vapor vent passage, is used to admit and temporarily adsorb fuel vapor from a vehicle fuel tank during refueling. The canister also has a first fuel vapor and air flow passage for venting the canister and introducing ambient air (in the reverse flow direction) for removing vapor stored in the canister during tank refueling. The canister has a second passage for conducting air and purged vapor from the canister to the operating engine. The first and second passages are opened only during engine operation for purging of stored fuel vapor. The first flow passage is selectively opened when the tank is being refueled. The sealed fuel system eliminates diurnal fuel tank vapor generation and canister bleed emissions.

Abstract: The engine or powertrain control module of a vehicle remains electrically powered after the engine is stopped and is used to assess whether there is a leak in the evaporative emissions control system. Fuel tank temperature and pressure data, as well as fuel level data, is analyzed over a brief period of time by module and, if ambient conditions are suitable, the vent on the fuel adsorption canister is closed by signal from the module. The system is thus sealed and the module then analyzes the system pressure changes over a second brief period as the fuel cools by heat loss to detect the vacuum that will occur if the system has no leak.