This publication is the first in a series of three texts for a diesel mechanics curriculum. Its purpose is to teach the basic concepts related to employment in a diesel trade. Six sections contain 29 units. Each instructional unit includes some or all of these basic components: unit and specific (performance) objectives, suggested activities for teachers and students, information sheets, transparency masters, assignment sheets, answers to assignment sheets, job sheets, pencil-paper and performance tests, and answers to tests. Introductory materials include description of unit components, instructional/task analysis (psychomotor and cognitive skills to be learned), listing of needed tools and equipment, and reference list. Section topics are orientation (safety, basic shop tools and equipment), operating principles (diesel fuels, engine lubricants, coolants, bearings, seals), engine components (cylinder head assembly, piston and connecting rod assemblies, camshafts, gear train, engine timing, frames, cylinder blocks, crankshafts, bearings), auxiliary systems (lubrication, cooling, air intake and exhaust, starting, brakes and retarders), engine performance (operation and maintenance, diagnosis and testing, tune-up and adjustment, storage), and welding (arc and oxyacetylene). (YLB)