Engine starting system

A rich mixture having a low air-fuel ratio is combusted in a cylinder which is on a compression stroke at engine stop to produce a torque acting on an engine in a reverse running direction thereof and a mixture produced in a cylinder which is on an expansion stroke at engine stop is combusted after the mixture has been sufficiently compressed as a result of reverse running motion of the engine. Subsequently, an additional quantity of fuel is injected into the cylinder which was initially on the compression stroke when gas in this cylinder has been compressed due to the reverse running motion of the engine, so that a compressive reaction force exerted by the same cylinder decreases due to a cooling effect produced by absorption of latent heat by evaporation of the injected fuel.