Abstract: A fuel supply system for an internal combustion engine is disclosed which includes a single fuel injection valve provided at the area at which a plurality of branch passages of an intake manifold join, and a pressure regulator which regulates the pressure of the fuel supplied to the fuel injection valve in accordance with a vacuum pressure in an intake manifold.According to this system, during low load condition, the pressure of the fuel supplied to the fuel injection valve is held within a range of levels lower than that appearing during high load conditions, thereby increasing the duration during which the fuel injection valve is opened in synchronism with the operation of each cylinder. Thereby, this system makes it possible to uniformly supply fuel to each cylinder for all running conditions of the vehicle.

Abstract: An exhaust gas recirculation (EGR) control system for an internal combustion engine, in which an EGR control valve including a vacuum-operated actuator governs the flow of recirculated exhaust gas according to the admission of air into the engine. To accomplish the control with high precision, the control system includes a flow sensor which provides an electrical signal representing the volume flow rate of air in the induction passage and a control circuit for controlling the magnitude of vacuum for the EGR valve through the operation of an electromagnetic valve based on the signal from the flow sensor. Optionally the control system has another flow sensor which provides an electrical signal representing the volume flow rate of recirculated exhaust gas to the control circuit to accomplish a feedback control.