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Home >> Buick >> 1980 >> Skyhawk Base, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Electronic Spark Control & Electronic Module Retard Ignition System >> Testing >> Electronic Module Retard >> Without C4 System
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Without C4 System

  1. With engine idling and engine coolant temperature above 120°F, check engine timing. Disconnect EMR lead at EMR vacuum switch.
    NOTE: If engine vacuum drops below 4 in. Hg, the EMR switch opens to allow normal ignition timing.
  2. If timing advances, check EMR vacuum switch. If no vacuum is present, replace EMR switch. If vacuum is present, check vacuum hose connections at 6 port TVS switch. If OK, replace TVS switch.
  3. If timing does not advance, ground EMR lead. If timing retards, proceed to step  4). If timing does not change, check for an open circuit in EMR lead into distributor or connection at EMR module. If circuit is OK, replace EMR module and reset ignition timing.
  4. If timing retards 10° when EMR lead is grounded, the EMR module is OK. Connect EMR lead to EMR vacuum switch. Apply vacuum to EMR vacuum switch. Timing should retard 10° when vacuum is 4 in. Hg or more.
  5. With vacuum applied, and timing retards, EMR vacuum switch is OK. If timing does not retard, replace EMR vacuum switch.
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