GM Full-Size Trucks 1970-1979 Repair Guide

Spark Plug Wires

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TESTING



See Figures 1 and 2



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Fig. Fig. 1: Checking plug wire resistance through the distributor cap with an ohmmeter



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Fig. Fig. 2: Checking individual plug wire resistance with a digital ohmmeter

At every tune-up/inspection, visually check the spark plug cables for burns cuts, or breaks in the insulation. Check the boots and the nipples on the distributor cap and/or coil. Replace any damaged wiring.

Every 50,000 miles (80,000 Km) or 60 months, the resistance of the wires should be checked with an ohmmeter. Wires with excessive resistance will cause misfiring, and may make the engine difficult to start in damp weather.

To check resistance, remove the distributor cap, leaving the wires attached. Connect one lead of an ohmmeter to an electrode within the cap; connect the other leak to the corresponding spark plug terminal (remove it from the plug for this test). Replace any wire w