Engine air-fuel ratio control method with venturi type fuel supply device and fuel control appliance including the method

An object of the present invention is to maintain stable air-fuel ratio on a venturi type fuel supply device, irrespective of the external load such as air-conditioner and electrical load, and to provide stable engine speed on idling state. A venturi type fuel supply device comprises a venturi chamber (400) located in the upstream of a throttle valve (202) and a passage (201) for supplying air-fuel mixture gas into the venturi chamber (400). The passage (401) is further equipped with a variable air bleeder valve (208) for taking in air. When the operating state of the external load of the engine (201) changes, the opening of the air bleeder valve (208) is adjusted in accordance with the change so as to control the air-fuel mixture ratio of the mixture gas incoming from the passage (401) into the venturi chamber (400).