- 1). Remove the high tension lead from the distributor cap. Connect a new or known good spark plug to the end of the high voltage lead. Place the spark plug base on a good ground such as the engine cylinder head. Position the spark plug so the electrode is visible.
- 2). Turn the ignition key to the "start" position and crank the motor over. Observe the spark plug and look for a blue or bright yellow spark. If a strong spark is present, the ignition coil is good. If no spark is present, proceed to the next step.
- 3). Locate the ignition coil positive (+) terminal. Turn the ignition switch to the "run" position. Set the multimeter to the "volts" function. Place the red lead of the multimeter on the positive (+) terminal of the ignition coil. Place the black lead of the multimeter to an engine ground or battery negative (-) terminal. The multimeter should read either six or 12 volts depending on your vehicle specifications. If no voltage at all is present, then there is a problem with the primary ignition circuit to the vehicle that must be corrected.
- 4). Disconnect the positive (+) and negative (-) lead wires from the ignition coil using a combination wrench. Turn the multimeter to the "ohms" function. Place the red lead of the multimeter on the positive (+) terminal of the coil. Place the black lead of the multimeter on the negative (-) terminal of the coil. The multimeter should display a resistance of about 0.4 to 0.6 ohms.
- 5). Move the red lead of the multimeter to the coil output terminal while keeping the black lead on the coil negative (-) terminal. The multimeter should show a resistance of about 5000 to 7200 ohms. If the readings from the primary or secondary windings show a zero "0" or infinity "1" then the coil is bad and must be replaced.