This study was carried cut to get basic data of troubles in starting and supply of farm diesel engines in cold winter. The results of the study are summarized as follows: 1. As the result of farm survey. the proportions of farms which had starting problems or troubles in fuel supply in cold winter for the last 5 years were 38% for the farms with power-tillers and 32% for the farms with tractors. Most of the farms which had starting problems or troubles in fuel supply in cold winter used light oil for summer. spring or fall rather than for winter. 2. As the result of fuel supply test, fuel supply was stopped at -6$^{circ}C$ and -18$^{circ}C$ for summer light oil and winter light oil. respectively 3. The lowest temperatures of winter light oil for starting engine were -7.5$^{circ}C$ for power-tiller. -12.5$^{circ}C$ for tractor of 38ps, and -17.5$^{circ}C$ for tractor of 45ps. which were 5~7.5$^{circ}C$ lower than that of summer light oil. 4. The performance of engine starting and the trouble of fuel supply system at lower temperature were significantly improved by using winter hight oil rather than summer light oil.