Engine starting system

An engine starting system for automatically stopping an engine when automatic engine stop conditions are satisfied and for restarting the engine when engine restart conditions are satisfied includes a throttle valve for regulating intake air quantity and an automatic engine stop controller. When automatically stopping the engine, the automatic engine stop controller sets throttle opening K to increase the intake air quantity at first specified time t1 in an initial stage of automatic engine stop control operation, decrease the intake air quantity at second specified time t2, and detect a point in time when the engine lastly goes beyond compression stroke top dead center immediately before engine stop and increase the intake air quantity at third specified time t4 which is set at or later than the last point of going beyond the compression stroke top dead center.