Mercury 3W7Z-12029-AA Coil Assembly - Ignition

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To check the EI ignition system, disconnect the coil's electrical connector(s) with the ignition off and use an ohmmeter to measure resistance. If not, replace the coil. For this, disconnect the battery's negative cable, the ignition coil electrical connector(s), and remove the spark plug wires. Remove the ignition coil from the engine mounting bracket. During installation, apply silicone dielectric compound inside the rubber boot before inserting each spark plug wire into the ignition coil.

For the distributor type ignition system (Duraspark II and TFI-IV), start by checking the primary and secondary coil resistance. With the ignition off, disconnect the wires from the coil and connect an ohmmeter across the coil primary terminals. If the resistance is not within the specified range, replace the coil. Next, measure the resistance from the positive primary terminal to the case of the ignition coil. If the resistance is less or more than the specified range, replace the coil. To replace the coil, disconnect the battery cable, detach the wires from the primary terminals, unplug the coil secondary lead, remove the bracket bolts, and detach the coil. Installation is the reverse of removal. For the electronic distributorless ignition (EDIS) system, start by checking the primary and secondary coil resistance. With the ignition off, disconnect the electrical connector(s) from the coil and connect an ohmmeter across the coil primary terminals. If the resistance is not the same for all four tests, replace the coil. Next, connect an ohmmeter between the secondary terminals of each coil pack. If the resistance is not within the specified range, replace the coil. To replace the coil, disconnect the negative cable from the battery, disconnect the ignition coil electrical connectors from each individual coil pack, disconnect the ignition wires, remove the bolts securing the ignition coil, and install the new coil following the reverse of the removal procedure. For the integrated electronic ignition system (COP), follow the diagnosis outlined in section 6. When it has been determined that a coil needs replacement, unplug the coil, remove the retaining bolt, remove the coil, inspect the spark plug, check the coil harness connector terminals, and then replace the coil and reconnect the harness.

To replace the coil in the EDIS system, start by disconnecting the negative cable from the battery. Then, disconnect the ignition coil electrical connectors from each individual coil pack and disconnect the ignition wires. Remove the bolts securing the ignition coil and install the new coil following the reverse of the removal procedure.

After cleaning the wire, check for burns, cracks, and other damage.

Disconnect the electrical connector and remove the mounting bolt.

The ignition coils are sold individually

boot # F7TZ 12A402-AA comes separate