Abstract: Pumping element is an important component of a diesel fuel injection system. This project was carried out in Bosch. Ltd Adugodi, Bangalore. Using Pareto analysis, defects with highest percentage rejections are found. Barrel bore taper more and Honing Lines rejections were 2.5% and 1.8% respectively in the year 2013. Root cause analysis is done using Shainin Technique. Reason for the cause is analyzed and the solution is found. The solution is optimized by analyzing the Physics behind the problem. Optimized solution is validated for a calculated batch over particular period. After validation the solution is incorporated for daily production. The rejections were brought down by more than half.