This student guide is for Unit 3, Primary Circuit, in the Engine Tune-Up Service portion of the Automotive Mechanics Curriculum. It deals with how to test the primary ignition circuit. A companion review exercise book and posttests are available separately as CE 031 212-213. An introduction tells how this unit fits into the total tune-up service, defines new terms, and provides work activities on the introductory information. Eight performance objectives are covered: inspect points and condenser, remove and replace ignition points and condenser, remove and install the distributor, strobe the distributor and adjust advance mechanisms, overhaul and calibrate distributor, inspect and test primary circuit, remove and install coil, and remove and install ignition switch and resistor. Each objective is addressed in a separate section that includes these materials: introduction to the performance objective, performance checklist, list of tools and equipment needed to do the work activities for this performance objective, reading list, information sheets, and work activities that give hands-on practice in doing one part of the performance objective. (YLB)