PURPOSE: To hasten the restarting of fuel supply after cutting off said fuel supply on decelerating, by electronically controlling a bleed air to a slow jet provided on the upper course of a slow cut solenoid.

CONSTITUTION: Fuel is supplied from the float chamber 14 of a carburetor, via a main jet 13 and the closing valve 15b of its bypass, and from a main nozzle 12 as well as an idle nozzle 9 via a slow jet 6, a slow cut solenoid valve 2, and a slow port 8. Bleed air is supplied to the slow jet 6 via a main bleed 3a and the closing valve 15a of its bypass and, at the time of an ordinary operation, the supply of fuel and the control of air-fuel ratio is carried out by the opening and closing of a solenoid valve body 15. At the time of deceleration of an engine, the valve 2 of the slow cut solenoid 1 is closed and a large negative pressure is maintained in a passage 16 and, when the valve 2 is opened after deceleration is over, fuel in the jet 6 is immediately sucked out due to the large negative pressure, and, then, a bleed air is fed into the jet 6.