The lubrication characteristics of fuel pumps with spiral grooves are investigated by numerical analysis. The two-dimensional Reynolds equation is used to evaluate lubrication characteristics with variations in grooves and viscosity. Moreover, the equilibrium equation of moment and forces in the horizontal and vertical directions is used to determine the motion of the plunger. The lubrication characteristics of the fuel pump with spiral grooves are compared to those without spiral grooves. The lubrication characteristics of the pump are investigated by comparing the film parameters. The fuel pump with spiral grooves is effective for relieving any uneven pressure distribution surrounding the plunger and can improve the lubrication characteristics. The application of spiral grooves is shown to be more effective in a low-viscosity condition compared to in a high-viscosity condition.