This study addresses the contamination sensitivity test of a typical fuel pump for an automotive vehicle. The objective of the study is to find the contamination sensitivity coefficient of a fuel pump on specific contaminant particle sizes so that an optimal fuel filter could be selected. To achieve the objective, the degradation of discharge flow rate of the fuel pump is measured under the experiments of various contaminants size ranges of ISO test dust up to $80;{mu}m$. The fundamental theory of contamination sensitivity is introduced and the contamination sensitivity coefficients are estimated using the experimental data. Maximum contamination sensitivity coefficient of $5chi;10^{-6};L/min{cdot}Ea$ is found in the contaminant size range of $40;{mu}m~50;{mu}m$. The magnified picture of the surface of vane disc reveals that the abrasive wear is the principal cause of discharge flow rate degradation. Hence, this study reveals that a high efficiency filter for contaminant particles especially in the size range of $30;{mu}m~70;{mu}m$ especially should be used to maintain the service life of the fuel filter.