A method of fabricating a modular fuel injector permits the fabrication of the electrical group subassembly outside a clean room while a fuel group subassembly is fabricated inside a clean room. The method includes fully or partially forming one or more micromechanical structures multiple times on a first substrate. The basic objective of this invention is to create a viable alternative fuel source that replaces fossil fuels. The probe block is movable between a retracted position and an extended position within the interior chamber formed in the guide sleeve. The outlet opening of the recirculation line or admission opening of the intake air line opens into the intake air line and a swirl generating element andor a turbulence generating element is provided in the area of the admission opening of the mixing device.