Can't Get Enough
Join Date: Sep 1999
Location: Cotopaxi, Colorado
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Re: 88 YJ Ignition problems (cont)
You shouldn't have to worry about any voltages on those wires, they are input wires. The dist. supplies a small sine wave when it turns, this tells the module to turn on and off the coil. You can check this circuit with a test light hooked to a positive source, and induce a signal that will make the module fire the coil.
The first thing you should do is determine if the problem is on the positive side of the coil, or the ground side.
Start with the positive side. You should have battery voltage with the key on. If the voltage is only 9 volts or lower, don't worry about it, this is your ballest or resistance wire. During crank, you should get full battery voltage. This is the crank by-pass circuit. You should hook up a voltmeter or better yet, a testlight to the positive side of the coil, and see what it does when it dies. It is common for the bulk-head connector to come loose and correded with this circuit. Also, check the ignition switch under the dash if you loose this circuit. If there is a fusable link, it would be on the start solenoid's positive side.
If the problem is with the negative side of the coil, you fool around with the ign. module circuit. I would check some of the updated posts on the nutter by-pass. There shouldn't be any problem with returning the wires to their positions on the pcm. The pcm only retards the spark about 4 to 6 degrees. This is determined by the 4 and 10 inch vacuum switches. If you simply unplug the connecter there, the computer will have no effect on spark retard. This is why the data tag tells you to disconnect it when you set base timing. If you truely wanted to totally disable the pcm, you should get a "blue connector" ign. module, and wire it like a Ford. These modules are much cheaper, but the connectors arn't the same.