This manual covers a range of diesel engines, including the SD20, SD22, SD23, SD25, and SD33 models. These robust engines have powered various vehicles and applications, from the Cedric and Datsun pickup trucks to marine applications and industrial equipment like forklifts and light trucks. Known for their reliability and durable construction, these diesel powerplants have been utilized in diverse environments, including remote agricultural stations, demonstrating their consistent performance and enduring utility across decades of service and multiple vehicle platforms. The comprehensive content within this manual is designed to provide essential guidance for the maintenance, repair, and understanding of the specified diesel engines. Detailed sections on disassembly, component identification, repair procedures, inspection criteria, assembly, and general service practices are included. Furthermore, relevant technical specifications and recommended tools are outlined to assist owners, mechanics, and technicians in effectively managing the upkeep and operational integrity of these engines.