The article touches upon the issues of the operating process in the elements of the external gear pump modeling. The external gear pump is the part of the gas turbine engine and pumps a low-viscosity fluid – kerosene. The article shows that sleeve bearings in such pumps continue to operate at boundary friction modes while rotation speed is increased. It also shows that the end and radial clearances are variable, and the drain system is not optimal which prevents the modeling of the system by classic approach. The main elements of the pumping unit of the external gear pump are described in the article. A simplified geometric model, which forms the basis for the analysis of the pump operation, is given as well. The problems arising during the design stage, fine-tuning, and operation of external gear fuel pumps are briefly described. A preliminary analysis of the design methods showed that several parameters of the working process are not studied well enough to provide the basis for optimal construction design and its qualitative assessment within the design stage. The description of gears operation, the system of end clamping, end, and radial plain bearings is given. The analysis of pressure distribution models is given. The analysis takes into account pressure distribution from linear distribution in the delivery chamber to the pressure drop on one tooth. Distributions from different calculation methods and literature sources are compared as well. The features of bearing loading and the conditions of their operation and lubrication are described. Based on the preliminary calculations, recommendations in the literature, and experimental data, the operation features analysis of the gear fuel pump of the gas turbine engine is carried out. There are defined problems that will provide answers to the main modeling issues in the article: pressure distribution in the intertooth displacement chamber during stationary and transient operating; fluid leakage through variable end clearances and radial clearances; dynamic of the gears and associated parts movement; the influence of external conditions (temperatures, pressures, external vibrations, etc.) on the operation of the pump in general.