US Patent 9677512 Systems and methods for reducing bleed emissions

A method for a fuel system is provided. A vacuum is applied to a fuel vapor canister side of the fuel system, and hydrocarbon breakthrough is indicated responsive to a fuel vapor canister side pressure inflection point indicative of a decay in fuel vapor canister side vacuum. In this way, an evaporative leak check module may perform a leak check on a fuel vapor canister, while hydrocarbon breakthrough from the fuel vapor canister may be indicated without requiring a dedicated hydrocarbon sensor in the canister vent line.