GM 94840127 Ignition Coil

If the engine is hard to start, misses at high speed, or cuts out during acceleration, the coil may be faulty. Ensure the battery and distributor are in good condition, the points are properly adjusted, and the plugs and plug wires are in good shape. Before conducting electrical checks on the coil, confirm it is clean and connections are tight and free of corrosion. Detach the coil high tension cable from the distributor cap, hold the end of the cable near a grounded part of the engine, turn on the ignition, and operate the starter; a bright blue spark should jump the gap. If the spark is weak or absent, check the coil's primary and secondary resistance. If the coil checks out but the engine still has issues, reversed coil polarity may be the cause. To check for this, remove a spark plug lead and hold it near the spark plug terminal while inserting a pencil between the ignition lead and the plug. For HEI ignition, remove the distributor cap and use an ohmmeter to check the primary coil terminals and secondary terminal resistance. If resistance readings are not as specified, replace the coil. For replacement, detach the battery cable, disconnect the high tension cable, and remove electrical connections from the coil terminals, marking them for correct reinstallation. Installation follows the reverse order, ensuring the center electrode is in good condition.

First, remove the distributor cap.