No Spark

I have a 91 jeep cherokee 4.0 six cylinder. I have no spark at all. I had this problem before and replaced the ecm, crank sensor, and coil. Still no spark. A guy told me to shim the crank sensor out a little and that worked for about 3 months. Now I am back to square 1. Is there any way to bypass the crank sensor it is such a pain to change. What else could be wrong. Thanks

That is one of the most common problems with this engine's ignition. Sometimes just removing the harness plug and reconnecting it will bring it back to life. If you do have to replace it again, use an OEM part. I don't like doing those even using a rack. A cheap aftermarket part could lack longevity. Although, it could be something else, I doubt it if you "shimmed" the existing sensor. The harness may be the culprit as well.