This paper discusses about the effective utilization of fluid structure interactions simulation for the pump stage development of Impeller type fuel pumps. Axial clearance between the rotating impeller and stationary components is crucial for the effective performance of the pump stage. Because of designed interference fit and operating conditions the stationary pump stage components tend to deform towards rotating impeller. Computational simulations are extensively used in the design stage to predict this deformation behaviour. As these components bear wide variety of loads like structural, thermal & hydraulic loads, it demands coupled simulation to be performed. Computational fluid dynamics simulation was performed initially to get the pressure load distribution and solved in a structural solver along with other structural and thermal loads to calculate deformation. With the Multi-physics simulation results, pump stage design was optimized for minimum deformation.