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Home >> GMC >> 1983 >> Jimmy 6.2 C >> Repair and Diagnosis >> Engine Performance >> System >> Vacuum Advance Spark Control System >> Description >> Trapped Vacuum Spark
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Trapped Vacuum Spark

Trapped vacuum spark is used on all models. A thermal vacuum switch (TVS) is mounted in cylinder head and used to sense engine coolant temperature. A vacuum check valve is mounted between manifold vacuum, distributor and thermal vacuum switch. The system maintains high vacuum levels to distributor during cold engine operation and cold engine acceleration.