OK guys, I'm having a really bizarre issue with my '89 XJ (Renix, 4.0, AW4, NP242). Here's a rundown of what's going on:

The truck has been sitting for about two weeks(this is normal, I only drive it occasionally), and was hard to start(cranked, but no start), so I did the usual and used my jump box to jump it. I drove it 4 miles, parked it for about a hour and a half, then got back in and drove the 4 miles home, no jump needed. As I was getting close to home, the radio shut off, then came back on. Then it started shifting strangely, but only did it once or twice.

Then it sat again for another two hours, and once again, it started fine and I drove it about 4 miles with no problem. Sat again for another two hours, got back in, fired up first time, and I made it most of the way home. Then the radio shut off again, only this time it would not come back on. Then the turn signals wouldn't work. Then I noticed that the transmission seemed to be slipping when it was in drive. So as I was sitting at a red light, I shut it off and tried to restart, but it acted like the battery was dead and would not start. Strange - it had no problem starting less than 10 minutes earlier. Thankfully I had my jump box, I jumped it, and it started fine. Radio came back on, still no signals, and still acted like it was slipping in D. Shifted down to 1-2, and it did fine, seemed OK in 3, too. So I drove it the 3/4 mile home, got it into the driveway, and tried to shut it off and restart it again. Same thing - no start. So I took the battery out, and ran it on the jump box alone, and it shifts normally, the radio works, and the signals work.

Here's what I have put together: Clearly this is an electrical issue, or it wouldn't affect the radio and the signals. Also, the power windows were slower than normal, now that I think about it. The shifting problem doesn't occur until the truck has been driven for a few miles.

I know vehicles can be strange when there is a low voltage situation, so I currently have the battery out and on the charger, thinking that it may be the issue. One thing I noticed that was different from other vehicles I have worked on was that when the battery was out and I was running it on the jump box, as soon as I disconnected the jump box, the truck shut off. In past experiences, I have run a vehicle with no battery after it was jumped without issue. I don't know if that is normal for these trucks, or maybe this signals an issue with the alternator?

Any help you guys could offer would be greatly appreciated.

 

You need an alternator..