The article presents a simplified methodology for testing Denso common rail electromagnetic injectors, which was based on an adjustment of idling fuel dosage. In order to determine the parameters significantly affecting this process, the design of experiments technique (DoE) was applied. Due to the non-linear course of the rates characteristics obtained on the diagnostic test bench, the trivalent fractional plan was used. Analysis of computational data has shown that the generated parabolic model is well suited to the actual measurement results, as the injector dosage is slightly out of projected values. The calculations were carried out in the STATISTICA computer program, which takes into account the specificity of the experimental theory methods and is one of the most universal tools available on the market. Innovation is the effective implementation of the proposed methodology in the repair process, which has not been taken into account in this regard yet.