Abstract: A system provides automatic starting of a locomotive diesel engine if the temperature drops toward freezing, which could damage the engine because of its water cooled nature, thereby saving fuel otherwise required when an engine is permitted to run continuously. Temperature sensing devices sense the temperature in the cooling water to sense a starting temperature, a shut-off temperature and a still lower temperature at which to provide an audible warning and drain the cooling water if freezing should be imminent. A circuit including a time delay relay is responsive to the sensing of the temperature at which starting is to be carried out for causing connection of the normally disconnected battery and energizing of the engine starter to initiate engine operation.