Pre-1983 Ignition

Here are diagrams showing the difference between the pre- and post-1983 ignition systems.

(Click the diagrams for more)

I'm told that the wiring on a YJ is the same, except for one difference in wire color --- The wire from MCU harness terminal #47, going through the firewall to the connector at the ignition module, is orange on my CJ, but is light-green on a YJ.

A Trick

Your buddy borrowed your timing light and never returned it? Here's a trick I learned from my brother. The timing can be set to surprising accuracy with a vacuum gauge. Hook the gauge to manifold vacuum and run the engine at curb idle. Rotate the distributor clockwise to retard the timing. Now slowly rotate it counter-clockwise to the point where you just reach the maximum vacuum reading. Back off (clockwise) until the vacuum drops by 1". Lock the distributor down. Timing can be set to within 1° using this method.

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