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Home › GMC › 1986 › Forward Control 7.4 W, Automatic, 475/M40 › Repair and Diagnosis › Engine Performance › Ignition System › Ignition System - HEI (Federal) › Overhaul › Reading Scope Primary Pattern

Reading Scope Primary Pattern

  1. Spark Zone - spark plug arcing.
  2. Coil and Condenser Zone.
  3. Dwell Zone - displays current through coil primary with module activated.
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