89 Cherokee Ignition Coil Replacement & Spark Issues

1989 Jeep Cherokee Pioneer 4.0L I6 Auto AW4 4x4 NP231 Renix

It seems old car electrical systems don't enjoy being marinated in mother natures fines muddy water soup. After the starter failed, I replaced it. Now it cranks, but won't fire. Lets check the distributor cap. Lot's of dirty water and corrosion, time to clean it up. No spark. Maybe the ignition coil failed. Two T20 Torx bolts to remove, then clean up the contacts and drop the new one in. Nope, still won't spark.
Time to check sensors since it won't fire. My best guess was that the CPS (Crankshaft Position Sensor) wasn't sending enough voltages to tell the computer when to fire, so it never did. After cleaning the electrical contacts of the CPS and a few others, it fired up. So check sensors before buying ignition parts...