Abstract: A fuel supply device for an internal combustion engine comprises at least one electrically controlled injector feeding fuel under pressure into the intake manifold of the engine and an electronic control circuit connected to sensors responsive to operating parameters of the engine, particularly the engine speed, and delivering periodic signals of variable duty ratio to the injector. The control circuit applies asynchronous electrical signals to the injector as long as the running speed of the engine does not reach a predetermined threshold value. The asynchronous signals have a frequency very much higher than that which the synchronous operative law would cause.