Diagnostic strategy for a fuel vapor control system

A method for operating a fuel vapor control system included in a vehicle having an internal combustion engine, the method comprising:

• fluidically isolating a fuel tank from the atmosphere and external components;
• if the pressure differential between a fuel tank pressure and an atmospheric pressure is greater than a first threshold value, providing fluidic communication between an evaporation canister region and the fuel tank;
• fluidically isolating the evaporation canister region from the atmosphere and external components after providing the fluidic communication;
• and
• if the time rate of change of a pressure within the isolated evaporation canister region exceeds a second threshold value, implementing an evaporation canister default mode.

A fuel vapor control system for a vehicle including an internal combustion engine, the system comprising:

• an atmospheric pressure sensor electronically coupled to a controller;
• a fuel tank including a fuel tank pressure sensor electronically coupled to the controller;
• an evaporation canister fluidly coupled to the fuel tank, the internal combustion engine, and a surrounding atmosphere;
• a pressure sensor coupled within an evaporation canister region and electronically coupled to the controller;
• a control system including the controller having code executable via a processor to:
• fluidically isolate the fuel tank from the surrounding atmosphere and external components;
• provide fluidic communication between the fuel tank and the evaporation canister region when a pressure differential between the fuel tank and the atmospheric exceeds a first threshold value after the fuel tank is fluidically isolated;
• fluidically isolate an evaporation canister region from the surrounding atmosphere and external components after fluidic communication is provided between the fuel tank and the evaporation canister;
• and
• implement a default mode when the time rate of change of a pressure exceeds a second threshold value and/or a pressure differential within the evaporation canister region exceeds a third threshold value.