GMC 10477944 Ignition Coil

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To check the High Energy Ignition System (HEI), begin by disconnecting the battery's negative terminal. Test the coil for opens and grounds. On the high scale, connect the ohmmeter leads; it should show a very high or infinite resistance value. On the low scale, check the coil's primary resistance, which should indicate a very low or zero resistance value. Also, check the coil's secondary resistance on the high scale; it should not show an infinite resistance. If any values are off, replace the coil. For removal, unplug the coil's high-tension wire and electrical leads, and remove the mounting nuts to take out the coil. The installation process is the reverse of removal.

To disconnect the cable from the negative terminal of a battery, detach first if not done earlier the high tension lead of the coil and primary wire connector. Then remove mounting fasteners to separate coil from engine. For 1996 through 2000 models, take away electrical connectors from ignition coil and ignition control module, and unplug coil wire from high-tension terminal. Remove ignition coil/module bracket mounting bolts and pull assembly out through engine. On a workbench, drill center of rivets holding coil to bracket, punch out rivets and remove coil off bracket. Screw new screws into bracket while retaining it with ignition coil. Finally put assembly back on engine and connect electrical connectors as well as fit in the wires into their respective terminals in the coil.

Connect the ohmmeter leads to both terminals of the pick-up coil lead and flex the leads by hand again. The ohmmeter should read a steady value between 500 and 1,500 ohms as the leads are flexed.

Disconnect the cable from the negative battery terminal.

Place the assembly back on the engine and connect the electrical connectors and coil wire.

Remove the retaining clip, lift the pick-up coil assembly straight up, and detach it from the distributor.

To check the Enhanced Distributor Ignition (EDI) System, start by detaching the primary electrical connector from the coil and ensure it receives battery voltage with the ignition key ON (engine not running). Use the ohmmeter's low scale to check resistance values for the coil. Connect the negative probe to the coil body and the positive probe to the primary terminal on the ignition coil; it should indicate infinite resistance. On the low scale, connect the ohmmeter leads to the primary terminals on the coil, and it should show a very low resistance value. On the high scale, connect one lead to the primary terminal and the other to the secondary terminal, referring to the specifications; it should not indicate infinite resistance. For removal, disconnect the battery cable, unplug the coil high tension wire and electrical leads, and remove the mounting nuts to take out the coil. The installation process is the reverse of removal.

If the ohmmeter does not indicate infinite resistance, it means the pick-up coil is defective and needs to be replaced.

Start by connecting one lead of an ohmmeter to the terminal of the pick-up coil lead and the other lead to the ground. Flex the leads by hand to check for intermittent opens, and the ohmmeter should always indicate infinite resistance.

Start by connecting one lead of an ohmmeter to the terminal of the pick-up coil lead and the other lead to the ground. Flex the leads by hand to check for intermittent opens, and the ohmmeter should always indicate infinite resistance.