In a method for testing and repairing an injector for injecting fuel into the combustion chamber of an internal combustion engine, wherein the injector includes a nozzle, a restrictor plate, and a control valve, and a nozzle clamping nut which holds together said parts and by way of which said parts are fastened to an injector body of the injector. The functional components—nozzle, restrictor plate and control valve—are separated from the injector body. A connection piece serves to connect the functional components to a test bench is screwed to the functional components with the aid of the nozzle clamping nut to form an injector module. The injector module is connected to a test bench and subjected to testing, and afterwards optionally repairing.