Method of starting spark ignition engine without using starter motor

There is provided a method of starting a spark ignition engine having multiple cylinders. The method comprises stopping fuel upon an engine stop request, introducing air and injecting fuel for restart into a first cylinder before the engine completely stops, and igniting the mixture of the air and the fuel in the first cylinder upon an engine start request. In accordance with the method, by introducing air and injecting fuel into the first cylinder before the engine completely stops, the mixture of air and fuel in the first cylinder may be homogeneous at the time of the engine start request. Also, there may also not be turbulence of the mixture then. Under these states of the mixture in the first cylinder, by igniting the mixture upon the engine start request, the mixture may be relatively slowly combusted. The slower combustion may decrease temperature of the combusted gas, while temperature of the cylinder wall is relatively low at that time because the engine stopped for a while. So, the slower combustion may reduce heat loss in the first cylinder because of smaller difference between the temperatures of the combusted gas and the cylinder wall. Consequently, more energy may be derived from the first cylinder to the crankshaft. Then if the first cylinder is on the compression stroke when the engine stops, as the compression stroke cylinder described above, the crankshaft may rotate more in reverse so that the expansion stroke cylinder described above may ascend more and compress more air therein to exert more reaction force from the compression. It also may combust the more air therein to generate more combustion energy from the expansion stroke cylinder. So, the more compressive reaction force and the more combustion energy may together increase the inertia of the crankshaft at the second top dead center.