Abstract: Electronically controlled fuel injection system for mixture-compressing, externally ignited internal-combustion engines, including at least one suction pipe connected via the intake valve path with at least one combustion chamber of the engine, an electrically controllable injection valve disposed at the suction pipe to supply the fuel, a measuring device effective in the suction pipe, and an electronic control circuit operatively connected at its input with the measuring member and at its output with the injection valve. The measuring device is an electro-optical spectrometer which analyzes the fuel-air mixture sucked in by the engine so as to determine the fuel-air ratio of the mixture, and the electrical control circuit is a comparison circuit which compares the mixture-dependent electrical output signals of the spectrometer with a preset desired value.