The selective catalytic reduction (SCR) system features with integrated high-pressure urea dosing pump to regulate the urea spray injection pressure for pertinent mixing of evaporated ammonia with exhaust gas mixtures in the diesel engine. This paper is a contribution to numerical simulation studies of external gear pumps using the immersed solid method for better understanding of continuously changing fluid fields and transient flow characteristics. A comprehensive set of data gained by the investigations from KATECH institute was executed in the present study, which led to an optimized CFD setup for realistic numerical simulation. Parametric analyses have been carried out for the gear speed and supplied urea liquid mass flow rate to find the behavior of pressure, mass flow rate, and velocity fluctuations in the domain. As a result, the pressure at the outlet reached its maximum with the increase in rotational speed, and the fluctuations grew.