The aim of this study was to develop and subsequently validate a simulation model of a Common Rail (CR) system injector. The study includes a description of simulation and experimental tests conducted under various injector operating conditions. Experimental tests were performed using the STPiW-2 test bench. The operating conditions of the injector were varied in terms of injection pressure and injector opening time. The injector model was developed using the Amesim software, where simulation studies were also conducted. The simulations focused on generating injection characteristics, specifically the volume of fuel injected per injection at pressures ranging from 20 MPa to 140 MPa in 10 MPa increments. Four such injection characteristics were obtained during both experimental and simulation studies, corresponding to injector opening times of 500 µs, 1000 µs, 1500 µs, and 2000 µs. Additionally, volume characteristics were generated under the same conditions. The validation demonstrated a high level of accuracy for the developed model. The obtained injection characteristics exhibited a correlation coefficient exceeding 90% in all four cases. The most accurately replicated injection characteristic was for the 500 µs injector opening time, achieving a correlation coefficient of 99%. Meanwhile, the simulation-derived overflow volume characteristic matched the experimental results with a correlation of 98%. For longer injector opening times, the correlation coefficients were slightly lower but remained satisfactory. The study concluded that for short injector opening times, the assumed model simplifications had minimal impact on the injected fuel volume at a given pressure. However, for longer opening times, discrepancies between simulation and experimental results became more pronounced. This divergence could be attributed to pressure variability within the injector during operation and associated hydraulic phenomena.