Systems and methods for a vehicle cold-start evaporative emissions test diagnostic

A method comprising:

• during vapor purging conditions, purging fuel vapors from a fuel tank through a first vapor storage device into an intake manifold of an internal combustion engine, venting a second vapor storage device to atmosphere and purging fuel vapors from the second vapor storage device through the first storage device into the intake manifold;
• in response to turning off the engine, venting the second storage device to atmosphere and routing fuel vapors from the fuel tank through the second vapor storage device but not through the first vapor storage device;
• and
• during a cold start of the engine, sealing the second storage device from atmosphere and routing fuel vapors from the fuel tank through the first storage device into the intake manifold of the engine.

A system comprising:

• an internal combustion engine having an intake manifold and an exhaust manifold, the engine driving a vehicle;
• a catalytic converter coupled to the exhaust manifold;
• a fuel tank having a fuel vapor outlet which is connected in series to a one-way check valve which is connected in series with a fuel vapor storage buffer which in turn is connected in series to a purge valve that is connected to the intake manifold;
• a fuel vapor storage canister having a load input connected to the fuel tank and a purge outlet connected to the one-way check valve, and a vent valve coupled to atmosphere;
• and
• a controller, storing instructions in non-transitory memory, that when executed, cause the controller to:
• during engine purge conditions, open the purge control valve and the canister vent valve;
• and during evaporative emission testing conditions, in which the catalytic converter is at a temperature below that needed for catalytic activity, start the engine, seal the vent valve, and open the purge valve until a predetermined negative pressure is reached in the fuel tank;
• and after the predetermined negative pressure is reached, close the purge valve and indicate undesired evaporative emissions are present if the fuel tank pressure exceeds a threshold pressure within a predetermined time after closing the purge valve.