The Fiat Tractor Series 90, encompassing models 115-90, 130-90, 140-90, 160-90, and 180-90, represents a line of robust and powerful heavy-duty agricultural tractors produced primarily in the late 1980s and 1990s. These machines were engineered with an emphasis on reliability and farmer-centric design, featuring typically inline 6-cylinder turbocharged diesel engines with displacements ranging from approximately 7.5L to 9.0L, delivering horsepower from 115 to 180 HP. Known for their strong torque output at lower RPMs, they were built to handle demanding agricultural tasks. The Series 90 tractors competed in a market that valued performance and durability, offering a significant evolution from earlier Fiat models with updated technology and comfort features for their time. This comprehensive workshop manual provides in-depth technical guidance for the maintenance, diagnosis, and repair of the Fiat Tractor Series 90. Covering a wide array of systems including the engine, transmission, hydraulic system, electrical components, chassis, and operator station, this 507-page manual is designed for professional technicians and experienced mechanics. It details engine overhaul procedures, gearbox and clutch servicing, hydraulic system maintenance, electrical system troubleshooting, and chassis adjustments. Furthermore, the manual includes step-by-step repair instructions, overhaul procedures, and diagnostic charts to assist in identifying and rectifying common issues, ensuring the longevity and optimal performance of these agricultural workhorses.