In the internal combustion engine, combustion characteristics were important from the point of the overall performance of the engine. Current paper investigates the influence of injection system parameters such as injection pressure (400,500 and 600 bar), start of pilot injection timing (35°, 40° and 45° CA bTDC), start of main injection timing (10°, 15° and 25° CA bTDC) and a quantity of percentage fuel injection (10:90, 20:80 and 30:70 in percentage) and their values on combustion characteristics of the small single-cylinder CRDI diesel engine. Combustion characteristics such as in-cylinder pressure, heat release rate, rate of pressure rise and mean gas temperature were considered. The effect of injection system parameters were discussed in details with the help of a graphs, plotted with respect to crank angle. It was observed that the taken injection system parameters improve the combustion characteristics of the engine, when compared to the conventional mechanical fuel injection system. By optimising these injection system parameters from performance and emission point of view definitely gives a large improvement in the overall performance of the engine.