Been having this puzzling issue for about a month now. Drove the jeep 160 miles from Syracuse to Buffalo, went to a restaurant for about 25 mins, came out and the jeep wouldn't start. No crank, just nothing. Battery is fine, though. The AAA guy jumped the starter and it started right up.

Took it to a local mechanic and he couldn't get it to not start again. Every single time he tried, it would start. He replaced some wired that were corroded, thinking it might have been the problem. I picked the jeep up and drove it for about 25 minutes on the highway. Went into a store for about 25 minutes, came out, and it wouldn't start. Got it towed back to the shop.

Once again, couldn't reproduce the no start. He installed a switch to bypass the NSS and ignition. Just goes right to the starter. Picked it up a few days ago and everything seemed fine. Last night, though, had another no start. Same conditions, too. Drove for awhile, stopped for a few minutes, wouldn't start. If you wait long enough though, it will start again. Usually about an hour or so.

When it starts up, it doesn't sound weird or anything, so we've been skeptical that it's a problem with the starter. Any ideas?

 

If waiting an hour or so after driving allows the starter to engage, (and you can repeat this) the starter itself is on the suspect list. Starters can fail this way. But I'd start with freshening grounds, just to eliminate that as a possibility. You're not wasting your time with freshening grounds; you are preventing future problems.

If after freshening grounds you still experience this symptom, I'd try swapping the starter relay located in the power distribution center (black box under the hood) with another one to eliminate that as well. These relays are all of the same part number so swapping is not a problem.

If freshening grounds and swapping the relay are of no help, I'd install a new (not rebuilt) starter.

Good luck and keep us updated!
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Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea, and the investment of your time in this procedure is always well worth it!

You can't tell much of anything by looking at ground connections!! You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. Be sure to remove all paint from any ground connections.

Start with the one on the back corner of the head, and where it attaches to the firewall, as it deteriorates over time and is an area that makes it susceptible to damage. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support.