Will fire up run like three seconds and cut off

It's in theft mode. Lock and unlock a front door with the key to turn the system of.

If you want the world's best OEM radio for your vehicle, look for a CD/cassette combo radio, even if you don't have cassettes. They were built by Mitsubishi for Chrysler and are real high quality. I stuck one in my 1994 Grand Voyager daily driver, and I had one in my previous 1988 Grand Caravan. The CD-only radios were built by Alpine and are much less desirable.

What you must watch for though is most of these radios have the standard Chrysler mounting ears. The 1993 to 1995 Jeeps use a different mounting ear pattern, so they're a little harder to find.