The engine speed controller of a conventional diesel engine is called a Governor. In order to control engine speed, the governor controls the amount of fuel using fuel rack. This study presents a development of speed control of D6114 diesel engine by using PID controller and a self-tuning fuzzy PID controller to overcome the appearance of nonlinearities and uncertainties in the systems. The self-tuning fuzzy PID controller is the combination of a classical PID and fuzzy controller. The mathematical model of the diesel engine is also done by using System Identification technique. First, PID controller was applied; then, a fuzzy logic control algorithm is used to estimate the PID coefficient in order to handle such uncertainties to produce a better control performance. Simulation tests were established using Simulink of Matlab. The obtained results have demonstrated the feasibility and effectiveness of the proposed fuzzy approach comparing to the PID controller. Simulation results are represented in this study