The effects of current mechanical fuel control systems on CVS emissions and maximum fueling rate smoke levels of light-duty Diesel engines were investigated. A comparison of emission projections made from steady state mapping data and actual vehicle emission test results indicated that modifications to the transient fueling characteristics had the potential to reduce particulate emissions by over 20%. An experimental Diesel electronic fuel control system was developed and used to assess the effects of fuel control system modifications on Diesel vehicle emissions and smoke levels. Modified governor characteristics were shown to provide a 37% reduction in particulate emissions relative to the baseline min-max governor. Maximum fueling rate calibrations were developed to provide constant smoke levels across the engine speed range.