Fuel injection anomalies observed during long-term engine performance tests on alternate fuels

A 25-75 blend (v/v) of alkali-refined sunflower oil and diesel fuel, a 25-75 blend (v/v) of high oleic safflower oil and diesel fuel, a non-ionic sunflower oil-aqueous ethanol micro-emulsion, and a methyl ester of sunflower oil were evaluated as fuels in a direct injected, turbocharged, intercooled, 4-cylinder Allis-Chalmers diesel engine during a 200-hour ERA cycle laboratory screening endurance test. Engine performance on Phillips 2-D reference fuel served as baseline for the experimental fuels. This paper deals with several aspects of the anomalous behavior of the fuel injection system and its effects on long-term engine performance as experienced during the operation with the alternate fuels. Particular attention was paid to the changes in injection timing and the rates of injection pressure. Furthermore, secondary injection phenomena, initial and final stages of the fuel injection, which have been recognized as very frequent causes of abnormal combustion behavior, were analyzed.