This technical manual provides specifications, operation descriptions, troubleshooting information, testing procedures, and repair instructions for John Deere 4200, 4300, and 4400 compact utility tractor diesel engines. The manual is organized into sections covering specifications, theory of operation for fuel, cooling, and lubrication systems, troubleshooting charts, engine system diagnostics, testing and adjustment procedures, and engine repair procedures. It is intended to help experienced technicians service and repair these diesel engines.