PURPOSE: To improve the control speed of an air-fuel ratio, by a method wherein, in a device which has an electromagnetic type injection pump attached to a carburetter, when an air-fuel from main fuel, air bleed of which is controlled, is controlled to the denser side than a given amount, a fuel injection pump is driven.
CONSTITUTION: A carbretter 7, having a piston 2 equipped with a needle 4, has a means, injecting and feeding fuel from a float chamber 19 to an intake air pipe 6 with the aid of an electromagnetic fuel pump 29, in addition to a main fuel system 20. In a control device 54, an air bleed amount of a main fuel system is controlled by electromagnetic valves 21 and 22 by means of various inputs from an 0 sensor 41 so that an air-fuel ratio is adjusted to an optimum given value responding to an engine operating state. In this control, when a difference between a desired air-fuel ratio and an actual air-fuel ratio is widely deviated to the lean side, the electromagnetic type fuel pump 29 is driven in priority to control of air bleed for enrichment, and this improves the control speed of an air-fuel ratio.
KASUYA KAZUSATO
KOBAYASHI KOICHI
ASADA YUKITOSHI
