Method and system for fuel vapor control

A method of monitoring a vehicle fuel vapor recovery system including a fuel tank coupled to a canister, comprising,

• under a first condition, applying a pressure in the fuel tank before applying the pressure on the canister;
• under a second condition, applying a vacuum on the canister before applying the vacuum on the fuel tank;
• and
• under either condition, indicating degradation based on a change in a fuel vapor recovery system pressure value upon application.

A method of monitoring flow of fuel vapors and/or air through a vehicle fuel vapor recovery system including a fuel tank with a refueling valve on an outer body of a vehicle, the fuel tank coupled to a canister and an engine, the canister coupled to an engine intake, and further coupled to a vacuum accumulator, the engine coupled to a battery and selectively operated in response to a battery state of charge falling below a threshold, the method comprising,

• during a first engine-off condition, when a fuel tank absolute pressure is greater than a threshold, applying a pressure on the fuel tank before applying a pressure on the canister;
• during a second engine-off condition, when a fuel tank absolute pressure is lower than the threshold, monitoring a change in fuel tank and canister pressure upon applying a pressure on the canister before applying a pressure on the fuel tank;
• and
• during the first engine-off condition or the second engine-off condition, indicating degradation based on a monitored change in fuel tank and canister pressure.