Engine start system for use in idle stop system for automotive vehicle

An engine start system designed to restart an engine when an engine restart request is made before complete stop of the engine following an engine stop request, comprising:

• a pinion gear which is movable between an engaged position where the pinion gear engages a ring gear coupled to a crankshaft of an engine and a disengaged position where the pinion gear is disengaged from the ring gear;
• a solenoid which is supplied with electric power to move said pinion gear from the disengaged position to the engaged position;
• a starter motor which is supplied with electric power to rotate said pinion gear;
• a one-way clutch disposed between said starter motor and said pinion gear, said one-way clutch working to transmit torque from said starter motor to said pinion gear and block transmission of torque from said pinion gear to said starter motor;
• and
• a controller working to control supply of the electric power to each of said solenoid and said starter motor, when an engine restart request is made, said controller perform a decision task, a first power supply task, a condition decision task, and a second power supply task, the decision task being to decide whether a speed of the engine is lower than or equal to a preselected gear engageble speed at which said pinion gear is engageble with the ring gear or not, the first power supply task being to supply the electric power to said solenoid when the decision task decides that the speed of the engine is lower than or equal to the preselected gear engageble speed, the condition decision task being to decide whether a given condition is met or not after the first power supply task is made, the second power supply task being to supply the electric power to said starter motor when said condition decision task decides that the given condition is met.