See Figure 1
- Connect an ohmmeter between the TACH and BAT terminals in the distributor cap. The primary coil resistance should be less than one ohm (zero or nearly zero).
- To check the coil secondary resistance, connect an ohmmeter between the rotor button and the BAT terminal. Then connect the ohmmeter between the ground terminal and the rotor button. The resistance in both cases should be between 6000 and 30,000 ohms.
- Replace the coil only if the readings in Step 1 and 2 are infinite.
These resistance checks will not disclose shorted coil windings. This condition can be detected only with scope analysis or a suitably designed coil tester. If these instruments are unavailable, replace the coil with a known good coil as a final coil test.
The ignition coil is designed to operate without an external ballast resistor. Inspect the coil for arcing. Test the coil primary and secondary resistance.
Measure the primary resistance as follows:
- Connect an ohmmeter between the positive (+) and negative (-) terminals (the terminals which are connected to the engine wiring harness) on the coil.
- To test the secondary resistance, connect an ohmmeter between the positive (+) coil terminal and the high voltage cable terminal on the coil, then, measure the resistance between the positive (+) coil terminal and the coil case; the resistance for the case should exhibit infinite resistance.
- For coils manufactured by Diamond, the primary resistance at 70-80°F (21-27°C) should be 0.97-1.18 ohms and the secondary resistance should be 11,300-15,300 ohms.
- Coils built by the Toyodenso company should exhibit a primary resistance at 70-80°F (21-27°C) of 0.95-1.20 ohms and a secondary resistance of 11,300-13,300 ohms.
- Replace any coil with a new one if it does not meet the specifications.
- If the ignition coil is replaced with a new one due to a burned tower, carbon tracking, arcing at the tower, or damage to the terminal or boot on the coil end of the secondary cable, the cable must also be replaced with a new one. Arcing at the tower will carbonize the nipple which, if it is connected to a new coil, will cause the coil to fail.
- If a secondary cable shows any signs of damage, the cable should be replaced with a new cable and new terminal. Carbon tracking on the old cable can cause arcing and the failure of a new coil.
Removal & Installation
- Disconnect the feed and module wire terminal connectors from the distributor cap.
- Remove the ignition set retainer.
- Remove the coil cover-to-distributor cap screws and coil cover.
- Remove the 4 coil-to-distributor cap screws.
- Using a blunt drift, press the coil wire spade terminals up out of distributor cap.
- Lift the coil up out of the distributor cap.
- Remove and clean the coil spring, rubber seal washer and coil cavity of the distributor cap.
- Coat the rubber seal with a dielectric lubricant furnished in the replacement ignition coil package.
- Reverse the above procedures to install.
- Make sure that the ignition switch is in the OFF position.
- Tag and disconnect the coil wire and the connector on the side of the coil.
- Remove the nuts holding the coil and bracket assembly to the engine and lift out the coil. The coil may be riveted to the bracket, to remove it will require drilling the rivets and punching them out.
- Position the coil on the engine and tighten the nuts.
- Engage the coil wire and electrical connectors.