Today I went to start my xj and it started just fine, but the radio wouldnt turn on and none of the gauges would move. I have a 1999 xj. The little screen would not light up but all the lights on the dash worked as they should. I shut it off to go take a look online and see if I can find a solution. I went to turn the key again to see if it fixed itself and it would not start. I jumped the battery and it fired right up, but should shut the engine off any time I took my foot off the brake. Does anybody know what the issue could be?

Start with a thorough cleaning and tightening of all your engine grounds and battery cables. It sounds like a loose battery cable may be in play here, but you need to check that stuff just to have a solid base for further troubleshooting.

All the battery cables are on tight and they're clean. I just double checked and they all look good. I also went through the fuses and they're all good

I just solved it somehow. A fuse for the reverse lights was blown so I figured I'd just fix that while I was working on the fuses and the gauges started working

The XJ is a trainwreck when it comes to the wiring, so if that was the fix, it wouldnt surprise me. They act funny sometimes for the stupidest of reasons. Obviously, keep an eye on things.

My XJ's wiring looked like a birds nest with wires everywhere. There was even bandaids used as electrical tape on the radio that i found a few weeks ago when it wasnt working. I took out close to 25 feet of random wires that went to absolutely nothing a few days ago. I guess that's what you get in a $900 XJ