Oil pressure gauge reads low or 0:
Comments on 97 TJ 4.0L Oil Pressure - Pirate4x4 Forum
My 97 TJ has been doing the same thing for years now. At first I was worried about it now I just ignore it. Engine runs strong no knocks or noises. I'll be honest with you though when it first happened it scared the shit out of me.
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Well my TJ just started doing this about a month ago and I finally went out and bought a brand new oil pressure switch. I put it on yesterday and drove it around today and the CHECK GAUGES light came back on and the oil pressure is at 0. Anything over idle i get oil pressure but never reaches 40.
  I put a mechanical gauge on it and upon starting with a cold motor the psi was right at 50psi. Half way warmed up it was at 40. Closer to 200 degrees it was down to 25. After I drove it around the block and really warmed up the oil it was between closers to 10psi on the mechanical gauge.
  I then disconnected the mechanical gauge and reinstalled the new oil pressure sensor and reconnected the wiring. I started the jeep back up and the gauge reads 0 at idle. I rev it up and the psi doesn't go over 25.
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I ended up replacing the oil pump in my Jeep. After I replaced it, the Jeep developed a faint knocking sound coming from within the oil pan. I'm almost positive it's either crank or rod bearings. I do have HIGH, normal oil pressure now though.

I have talked to a lot of people with 97s and most of them do it.
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On mine, it's just the oil guage. And it's only in that first few seconds upon start-up or re-start. A mechanical guage is a very good idea though. It would surely be more accurate. And as far as knocking and tapping...I have absolutely no knocking. There's a little tapping, which is constant and faint. But this just sounds like normal lifter/valvetrain noise to me. I did some rsearch a while back on the tapping, and everyone seemed to conclude that it was normal with all of the 4.0's.
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Comments at Low oil pressure - JeepForum.com
We decided it was simply the engine. Instead of paying $1500 for a new rebuilt one(next year a Stroker Baby!)... we put in Diesel Oil. It's thicker so it keeps the pressure up.   Been running that for three months now, 95% of the time I have normal oil pressure on start-up and running.
  The rare time it doesn't show it right off, after a little revving it shoots up and we're good to go.
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Comments at Jeep Wrangler Forum
Some cheaper filters use a rubber anti-drainback valve (ADBV). Try to buy a filter with a silicone ADBV.
  Lots of google info on this, and I have had trouble with dry starts on several vehicles.
  I think (but research it on your own) that WIX filters are silicone ADBV, and I know the Purolator Pureone premium filters do as well. Basically, you have zero oil pressure at startup if the filter has drained itself of oil since the pump has to fill the filter before pressurized oil gets to the rest of the engine.

Oil Pressure maxed out:
Your oil pressure gauge is not really a gauge; it's more of an idiot light with a needle. It could be a voltage issue at the sending unit. Take your jeep to a shop with a two way scanner and have them go in and check to make sure your cam and crank sensors are in synch and go from there. You still need to address that issue since it is what appeared first. Investigate...don't just throw parts at it hoping you'll fix it.

See oil

AAA would only pay $50 and the locksmith they contacted said it would be $250 (He claimed it was a problem common to most chrystler vehicles that the wafers go bad (wafers are used in place of tumblers on some locks see www.wilton.force9.co.uk/lock/mechanism2.htm).
It cost $225 during normal working hours less $50 from AAA. I checked the price at the jeep dealer and the lock and wafers are $140. I couldn't find anything on cartalk's web site or via a google, so it may not be as common as the locksmith said. The jeep dealer said he didn't think it was that big of a problem but they stocked 8 sets (they work in some dodges and jeeps) so there was fair demand for them. I only took him a minute to pull the cylinder out with a special tool (he didn't have to take the steering colum apart which I would have done to try and fix it myself).

Lessons:
1. They told me you can sometimes get it to work by tapping the end of the key with a screwdriver or your shoe then wiggling it around, but it will eventually freeze up so you need to get it fixed right away.
2. It may be just a cheap to have a locksmith come on a service call as getting the lock yourself and having a gas station install it, assuming you can get it running temporairly.