FUEL CUT-OFF CONTROL DEVICE

PURPOSE:To make it possible to eliminate a risk of unburnt detrimental gas remaining in exhaust gas, by cutting off the supply of fuel when the engine load is below a predetermined value, even though the opening degree of a throttle valve exceeds a predetermined value. CONSTITUTION:A ECU 28 controls the cut-off of fuel when an idle switch is turned on and the rotational speed of an engine exceeds the lowest rotational speed by a predetermined value. Further, the ECU 28 also controls the cut-off of fuel if an intake-air pipe vacuum detected by a pressure sensor 51 is lower than a reference value which is changed in accordance with the engine rotational speed, even through the idle switch 46 is turned off. At this time a valve 26 is fully closed by means of a step motor 27 to close a first passage 24, and an actuator 32 is driven to fully close a power valve 31 which therefore closes a second passage 24. With this arrangement, even if a throttle valve 43 is released, a carburetor does not feed fuel.