The potential sources of hydrocarbon (HC) emissions from a single-cylinder, divided-chamber diesel engine were investigated in this study. To evaluate the relative importance of these sources, the variations of HC emissions with engine speed, air-fuel ratio, combustion timing, intake-air temperature, coolant temperature and oil temperature were examined. Included in the diagnostics of this investigation were: ignition-delay measurements, combustion-chamber surface temperature measurements and heat-release modeling. Lubricating oil was found to contribute significantly to HC emissions. In addition, the results suggested that bulk quenching of flame and non-flame reactions is a primary source of HC emissions. On the other hand, lean mixing during the ignition delay period and wall interactions appear to be secondary sources.