1. A method for diagnosing a fuel system including a plurality of electric fuel delivery units that are submerged on an inlet side in a fuel supply contained in a fuel tank, and that, on an outlet side, deliver a fuel in a fuel line to an internal combustion engine, comprising the steps of: performing one of the steps of: directly measuring currents of the electric fuel delivery units in an analysis unit, and indirectly measuring the currents in the analysis units; comparing the currents to one of each other and to threshold values; and outputting a diagnostic signal as a function of a result of the comparing step.