Cold start, wouldn't crank. The only sound was clicking from the rear, probably the fuel pump. It ran thru System Check, and CHECK ENG stayed on. Got the same result in both P and N. Battery was fine.
Let it sit for an hour. Then it started and ran normally, with no CHECK ENG. Has been fine for 3 days.
Is this a sign of something worse to come? Thanks!!

 

It is probably going to happen again. Check the several connections from the battery to the engine fuse panels. Loose and/or corroded high current connections are a common problem.

 

Neutral safety switch is my bet if the battery is good and you have full gauge readings...jiggle in P or N next time and turn the key w/o waiting an hour That is a random one, which can be looooong times inbetween occurrences, or happen twice in a row frustrating issue.

 

these cars have beautiful bodies on them. i wish there was a way to clean out that engine compartment and just put a whole new engine and setup in it. like a 5.o with a standard transmission like on hot rod t.v.

 

Oh, there is. Check the forum for recent posts about swapping in a GM V-8 unit.

 

I'd bet on a loose or bad connection before I started looking at the electronics in the car. This kind of symptom is common enough in all cars, I experienced it myself in a 1963 Corvair (NO electronics, unless you consider the transistors in the radio). Found the positive battery cable clamp wasn't QUITE clamping down on the battery post. Nut was so tight it almost twisted off, and felt snug, but found that all I was doing was clamping the two sides of the connector together. It wasn't until I replaced it with a new cable, where the connector solidly clamped onto the terminal that the problem went away.

 

yeah i seen the post of the v8 and it just dont seam worth the money. i would rather just get the 4.0 and gear box together. im looking aroung 3000 for a piece of mind.

 

Here's the rest of the story.
I called my independent Jag mechanic about this. He said could be a bad chip (or maybe he said code) in your key. I said Aha, brilliant, but I'm using the extra key you sold me. We both laughed.
Anyway, later I was in for service and he checked the electrical gremlins you all suggested. Turns out the negative battery cable was loose on its post. Dumb, simple, but cheap.
So.......now we know.
Thanks for your suggestions!!!!!!!!!!!