At the time of exploitation, the geometrical position of the control valve changes as a result of wearing, which leads to a change of residual electromagnetic gap stroke and force of control valve spring. The following study measures the hydraulic characteristic changes, based only on common rail injector increased stroke of control valve and residual electromagnetic gap. The results show that the increasing of control valve stroke and residual electromagnetic gap increase the fuel flow rate and return fuel flow. Increased fuel flow rate and return fuel flow are presented with short injector signal time and lower levels of working pressure. The increasing is lower with longer injector signal time and high level of working pressure. The follow-up results are practically significant by common rail electromagnetic injector diagnosing and repairing.