The paper presents experimental research on a 4-stroke, 3-cylinder, turbocharged AL25/30 Diesel engine. Research consisted in investigating the effect of the geometry of the fuel injectors on the exhaust gas composition from the engine. During measurements, the engine was operated with a regulator characteristic of a load range from 40 kW to 280 kW, made by electric water resistance. The engine was mechanically coupled to the electric power generator. Three observations were made for each engine load, operating with fuel injectors of varying geometry. All considered types of injectors were installed on all engine cylinders. Mentioned injectors differed in the size of the nozzle holes diameters, holes numbers and angles measured between the holes axis. Engine performance data were recorded with a sampling time of 1 s. Cylinder pressure and fuel injection pressure on the front of each injector were collected also. The composition of the exhaust gas was measured using an electrochemical analyzer. According to the results, the change of fuel nozzle geometry results in a change in fuel spraying and evaporation and consequently changes in the course of the combustion process. The effect of this is the change of the composition of the exhaust gas.