The paper presents experimental and model research related to the fuel spray - wall interaction in terms of pressure and air back-pressure variability. Using a constant volume chamber the authors performed a qualitative and quantitative analysis of the fuel spray reaching the piston. The experimental research was supported with a model research using the FIRE 2010 software by AVL. On this basis the fuel concentration and its distribution in individual areas of the combustion chamber were determined (in the piston combustion chamber). A greater impact of the injection pressure (rather than the back-pressure) on the fuel spray distribution in the combustion chamber was observed and on the fuel spray interaction with the chamber walls in the piston.In such a case the problems of the contact of a liquid fuel with the cylinder walls and/or the combustion chamber walls is becoming increasingly important in terms of the fuel film formation and HC emission intensification. This problem intensifies when Start/Stop systems are used (during engine restart under lower temperatures of the combustion chamber walls and when injecting fuel divided into a higher number of doses.The results of the experimental research were also used for the simulation model and the results of this simulation were used for the evaluation of other physical quantities (diameter of the droplets) that could not be ascertained through the results of the experiment.