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Home › GMC › 1987 › Forward Control 6.2 J, Standard › Repair and Diagnosis › Engine Performance › Ignition System › Ignition System - HEI (CARBURETED Models) › Typical Oscilloscope Patterns › Reading Scope Primary Pattern

Reading Scope Primary Pattern

A) Spark Zone - spark plug arcing.
B) Coil & Condenser Zone .
C) Dwell Zone - displays current through coil primary with module activated.