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I just ohm them out. If there are any questions, I swap the coil with a working one to see if the dead one moves with the swap. If all are dead it's usually the module, cam or crank sensor (I have run across very few ECM failures). The sensors can also be checked with an ohmeter. After 100K I consider them highly suspect. They can be a pain!
Raise the hood of the car. Take the coil wire loose and hang it above the intake. Place some tuna in the end of the wire & wait for the neighbors #@%@&$#" cat to come over & eat the tuna. When he bites the tuna hit the switch. If the cat jumps off the engine then the coil is bad, if he gets knocked off the engine it's good. If he lays on the ground & doesn't move it's real good !!! :D
Put a .05 mfd capacitor across the primary wires (yellow and red). You can use a capacitor from an old point contact distributor. Clip a test lead on either of the primary leads and rest the other end about a half inch from the high voltage terminal and pulse the primary with 12 volts (from your car battery is ok). You should get a nice blue white snappy spark every time you break the 12 volt connection to the primary wires.
Raise the hood of the car. Take the coil wire loose and hang it above the intake. Place some tuna in the end of the wire & wait for the neighbors #@%@&$#" cat to come over & eat the tuna. When he bites the tuna hit the switch. If the cat jumps off the engine then the coil is bad, if he gets knocked off the engine it's good. If he lays on the ground & doesn't move it's real good !!! :D