A little more detail is needed. What exactly is it doing or not doing? Is it turning over and not starting or is not even turning over? What preceded the condition? Have you checked to see if it is throwing any codes? Let us know so we can help.
1991 YJ 4.0L, K&N air filter, SS headers, 31X10.5, Congo Cage, etc...
When all hope is lost, and you have run out of options, you can always break out the "HOLY HAND GRENADE"!!!! It may not fix it, but you will feel a lot better.