Fuel injection system

A fuel injection system for a mixture compressing internal combustion engine with spark ignition having a fuel injection nozzle for continuous fuel injection, an air intake duct, and an adjustable throttle valve in said intake duct, comprising:

• a flow sensing element in the intake duct arranged to move in accordance with the quantity of air flowing through said intake duct;
• a fuel metering valve, actuated by said flow sensing element, for dispensing a quantity of fuel which is substantially proportional or related to the quantity of air;
• means for maintaining a substantially constant pressure difference across the metering valve including a pressure sensitive valve having two chambers separated from each other by a movable partition element, and a differential pressure control valve which also has two chambers separated from each other by a movable partition element;
• the first chamber of said pressure sensitive valve being subject to the pressure downstream of said metering valve, and comprising a valve aperture controlled by the associated partition element, said first chamber communicating with the fuel injection nozzle through the valve aperture;
• while the second chamber of said pressure sensitive valve communicates with the first chamber of said differential pressure control valve;
• a spring-loaded valve element element which is controlled by the partition element of said differential pressure control valve;
• a return line, said first chamber of said differential pressure control valve communicating with said return line via said spring loaded valve element, while the second chamber of said differential pressure control valve is actuated by the pressure upstream of said metering valve, and the partition element of said differential pressure control valve is actuated on both sides by resilient elements, whose loading stress can be varied according to engine operating parameters.