In order to meet the China’s PHASE III and emission legislations, Electronic Unit Pump (EUP) system Ⅳhas been used by many diesel engine companies in China. The fluctuation on small cycle fuel injection quantity (SCFIQ) has great influence on the stability at small load operation of the diesel engine. A numerical model of the EUP system was built in the AMESim environment for the purpose of computing and analyzing the fluctuation on the SCFIQ. The influence of the different parameters on small cycle fuel injection quantity fluctuation (SCFIQF) has been obtained by the AMESim simulation model. By computing and analyzing, the quantitative percentage index of the influence on SCFIQ caused by different parameters also has been obtained. The influence percentage of injector characteristic parameters is from 35.8% to 60.8%, plunger characteristic parameters is from 20.3% to 34.8%, low pressure supply fuel characteristics is from 0 to 20.2%, and valve characteristic parameters is form 6.6% to 23.2% with the revolution range from 500r/min to 1300r/min. Based on the design of experiment (DOE) method, take the without interaction and interaction into consideration, the correlations of SCFIQ and different factors have been obtained and analyzed.
