Device for injecting fuel into combustion chambers, particularly of self-ignition internal combustion engines, wherein a fuel nozzle (4) generates an appropriate fuel jet and wherein are provided an air conduit device as well as a heating device. The fuel is injected together with an air flow contacting the heating device (3). The heating device (3) has at least two heating elements (10, 11, 25) of different efficiency, of which at least one element (10, 29) is used for rapid heating and of which another element (11, 25, 27) is provided for a prolonged utilisation.