the fully closed state l in fig5 after that the idle regulating valve 25 is actually maintained in the fully closed state with its closing operation stopped l to k in fig5 in contrast under the initializing control the idle regulating valve 25 which is assumed to be in the fully opened state is supposed to continue its closing operation to the intended fully closed state s 13 in fig3 see a dotted line in j to k in fig5 even if the starter 32 is maintained on j to m in fig5 in order to restart the engine 1 the fuel injection valve 18 is stopped from injection until the idle regulating valve 25 becomes fully closed k in fig5 in the program for s 12 in other words a supply of the fuel 17 to the main engine unit 2 by the fuel injection valve 18 is stopped unless the idle regulating valve 25 is brought in the fully closed state k in fig5 under the initializing control thereby preventing a first ignition from occurring in the main engine unit 2 s 14 in fig3 next the idle regulating valve 25 is opened to the predetermined initial opening n in fig5 in this case.