Good news is, the jeep is up and running again. The bad news is I ran out of ideas, and had to take it to the stealership.
However, this has been a great learning experience for me, and I think the finish may surprise some folks.
My no start (cranking and never starting) was due to a bad O2 sensor. It had fried, and stayed on, dumping too much gas into the motor, flooding it. The whole time I thought it was a fuel issue, but I didn't think it was getting to the injectors, turned out to be too much fuel. So, we can add a bad O2 sensor to the list of sensors that *can* keep the '91 4.0L from running.
Those sensors are:
1. Crankshaft position sensor
2. Camshaft position sensor
3. O2 Sensor.
Here's a test for the O2 Sensor (and tells you if you've got too much fuel) Unhook the fuel pump from the line, and try to start the engine, if it starts, it just might be your O2 sensor.
*as a side note, the jeep would not start when putting the pedal to the floor, hence putting it in WOT start. This shuts off the injectors to clear fuel from the motor, however, this didn't work for me
The stealership took 360 bucks from me to "diagnose," change O2 Sensor, and change the oil. A bummer, because I could have changed the sensor and the oil in less than an hour, but, I'd been working on the jeep for a full week before I took it in, and I was out of ideas. This was the jeeps first visit to a mechanic in the 125,000 miles I've owned it. Not bad really. I love the XJ, and
is an excellent resource for all of us owners. I definitely need to become a member to support this awesome association.
Feel free to shoot me any questions & thanks for everyone's ideas & help!