YJ not consistently starting. Timing problem suspected.
I have a 91 YJ 4.0 L with 150,000 miles on it that has not been constantly starting. The engine turns with no problems and when it does start it runs great. I treated the fuel thinking that it could be bad fuel after sitting for months and the problem persists. I have tried starter fluid which seems to work some times but not all the time. When it does not start, if I let it sit for a while it will start again. The reason that I am suspecting the timing is that I have seen smoke, or more likely exhaust coming from the intake. I'm hoping to diagnose and fix the problem without taking it to a shop.
Thanks for your help!