See Figure 1Ignition Coil Secondary Voltage Test
Connect the spark tester (D81P-6666-A or equivalent) between the ignition coil wire and engine ground, then crank the engine. If spark is present, the secondary voltage is sufficient. If there is no spark, measure the resistance of the ignition coil wire and replace the wire if the resistance is greater than 7,000 ohms per foot (30.4cm) of wire length. Inspect the ignition coil for damage or carbon tracking, then crank the engine with the distributor cap removed to verify distributor rotation. All Aerostar distributors rotate in the CLOCKWISE direction.
This test applies only to 1986-88 models.
Push the connector tabs to separate the wiring harness connector from the ignition module and check for dirt, corrosion or damage, then reconnect the harness. Do not remove the lubricant compound from inside the connector. Attach a 12 volt test light between the coil tach terminal and the engine ground, then crank the engine. If the light is on steadily or flashes, continue to the Ignition Coil Primary Resistance Test. If the light is off or on very dimly, go to the Primary Circuit Continuity Test.Ignition Coil Primary Resistance Test
Turn the ignition switch off, then disconnect the ignition coil connector. Check for dirt, corrosion or damage. Use an ohmmeter to measure the resistance from the positive (+) to negative (-) terminals of the ignition coil. If the reading is between 0.3-1.0 ohm, the ignition coil is OK; continue on to the Ignition Coil Secondary Resistance Test. If the reading is less than 0.3 ohm or greater than 1.0 ohm, replace the ignition coil with a new one.Ignition Coil Secondary Resistance Test
Use an ohmmeter to measure the resistance between the negative (-) terminal to the high voltage terminal of the ignition coil. If the reading is between 6,500-11,500 ohms, the ignition coil is OK; progress to the Wiring Harness Test. If the reading is less than 6,500 or more than 11,500 ohms, replace the ignition coil.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Disconnect the two small and one large wires from the coil.
- Detach the condenser connector from the coil, if equipped.
- Unbolt and remove the coil.
- Position the coil in place and install the retaining bolts.
- Attach the condenser connector to the coil, if applicable.
- Attach the 2 small wires and 1 large wire to the coil.
- Connect the negative battery cable.