A fuel control system for an engine includes a closing module and a purge control module. The closing module commands closing of a purge valve in response an engine speed transitioning from greater than a predetermined speed to less than the predetermined speed while the purge valve is in an open state. The predetermined speed is less than a predetermined target speed of the engine and is greater than zero. The purge control module transitions the purge valve from the open state to a closed state in response to the command.

The control device controls the air-fuel ratio of the air-fuel mixture based on the output value of the downstream-side air-fuel ratio sensor until a period from the engine startup start until the oxygen occlusion capability function is obtained in the catalyst elapses. The control device performs air-fuel ratio control of the air-fuel mixture on the basis of the output value of the upstream-side air-fuel ratio sensor after the elapse of the period from the engine startup start until the oxygen occlusion capability function is obtained in the catalyst.