Apparatus for assisting engine starting

An apparatus for assisting a hot-restarting operation of an internal combustion engine comprising a main air passage, a throttle valve inserted into the main air passage, a by-pass air passage by-passing the throttle valve, an engine starting switch, first means to detect the engine temperature, second means to detect ambient air temperature, and an auxiliary air introducing means inserted into the by-pass air passage and controlled by the engine starting switch and said temperature detecting means, the auxiliary air introducing means being a single valve having a control circuit therefor in which the first and second detecting means are connected in series with each other, and arranged such that air flow resistance through the by-pass air passage is reduced during the hot-starting operation of the engine under a condition in which the engine temperature and/or ambient air temperature are above respectively predetermined temperatures.