When you say it wouldn't crank does that mean the starter won't engage and turn the engine? Or the starter engages, turns the engine but the engine won't fire up and start?
If it's the second scenario, mine did that once. I ran the battery down trying to start it, had raw gas fumes coming from the exhaust. It turned out to be the ignition module. On my 87 YJ it is on the fender well under the windshield washer resevior.