Engine start control system

To detect the reverse rotation of an engine (E) according to output signals from a rotor sensor and inhibit fuel injection and engine ignition when the engine (E) is reversely rotated. Disclosed herein is an engine start control system having a function of reversely rotating a crankshaft of an engine (E) to a predetermined position after stopping the engine (E) for the purpose of standby for the next engine start. The engine start control system includes an injector for injecting fuel when the crankshaft reaches a predetermined angle, an ignition device (38) for igniting the engine (E) with predetermined timing after fuel injection by the injector, an ACG starter (50) functioning as a starter motor and a generator, a rotor sensor for detecting a rotor position of the ACG starter (50) to output multiple phase signals, means for determining a rotational direction of the engine (E) according to the phase signals output from the rotor sensor, and means for inhibiting the fuel injection when the engine (E) is reversely rotated.