I've got a 1998 Jaguar XJ 4.0 LWB Sovereign.

Yesterday whilst I was driving it I went over a decent size bump and got a few warning lights come up. Traction control failed, rear lights failed, etc. A few seconds later the engine died, power steering failed, power assistance for the brakes failed... coasted to a stop.

It no longer starts. Turning the key it makes a single, loud metallic click, but it doesn't try to turn over.

The battery doesn't appear to be dead, as the cooling fans ran for about 10 minutes after the engine died. I've checked the obvious things, battery terminals are securely connected, no visible loose wires around the battery or in the engine bay (at least what from what I can see, which is quite limited).

The AA came out and noticed that the negative terminal from the battery was hot, and said that suggested a bad earth somewhere, but they wouldn't know where to start looking for the problem. We tried jump starting it incase the battery was low but that made no difference- just a single loud click from somewhere in the engine bay.

It's going to a garage late next week, but just curious if there's some things I can check/try before then.

Thanks for the help

 

Welcome Tom and we're sorry to have to meet under these circumstances. You've put Cardiff in as your location, is that in the UK? This is important because N. American Jags didn't have the options available elsewhere in the world. Plus a local chap may be able to assist you if they see this?

Lets start with the simple things first and hope it didn't cause a worse issue as things get resolved. If you have a code scanner, please try scanning to see if any codes are stored and report those back here. If not, let us know, we'll try to give some direction for that.

If you have a hot cable, you have a bad ground (i.e. short). Depending on the type of bad ground, it could have shorted your battery, so get that checked. I would start with the alternator, it could have a bad terminal connection or the voltage regulator could have gone south and be feeding your system the wrong voltage? Both the battery and alternator can be checked at a local auto parts supply store.

While getting those checked and/or before trying to start the car again after that, check your fuses and relays. Pull out your service manual and review them...look for hot spots (browning) and/or corrosion.

You'll want to bookmark this site, its by a site member who's gathered tons of info from the years... JagRepair.com - Jaguar Repair Information Resource

Here's the electrical schematic pdf from that site... http://www.jagrepair.com/images/Auto.../jagxj1998.pdf

We understand your in need of resolving this issue, but when you get a chance it'd be appreciated if you introduce yourself and your Jag... https://www.jaguarforums.com/forum/n...-intro-must-5/

 

I would look at the cross connectors through the false bulkhead (back towards the cowling in the engine bay, right side -- for you, driver's side). If the wires are burned out, you will be dead no matter battery status. Local indy or dealer should pick it up quickly.

Check in the stickies, first threads, there is a document a guy in Canada did many years ago that talks troubleshooting electrical issues.

(just stole this from Bob in another thread): Copper or BRASS colored stud with nuts and insulators. BIG wire size for battery cable to starter/alt.

 

Is the attached pdf the one your talking about Jim?

 

If the negative battery cable is hot, it is most likely that the cable has developed resistance at its connection to the "eye" for the battery post or that there is some corrosion between the "eye" and the battery post. Remove the cable from the battery post and clean the post and the cable terminal. If after cable reconnection to the battery it still does not crank, wiggle the cable at its connection (crimp) to the "eye" and try starting again. If you then get the starter motor to crank (or briefly "tries" to crank), replace the negative cable.

The Jag battery cables are known to develop resistances at the crimps to the terminals, at both cable ends, and cause problem (even though the cables may look nice and shiny). I recently had the positive cable getting very hot near its terminal to the battery. Replacing it solved the issue.

 

I would check the engine ground. It is located about a foot or so behind the the passenger side front wheel. If the battery ground is hot when trying to start the problem may be there. It runs from the side of the engine to the chassis rail. A braided cable from the engine block.

 

If there is poor ground elsewhere, the battery cables would not heat up. The heat is generated right at the poor connection point.

 

I wonder if the MEGA FUSE lugs are properly secure then MS? ....or if its a MEGA FUSE itself?

 

Poor connection at the Mega Fuses would heat-up the fuse box and some heat would be transmitted down the positive cable to the battery. If the negative cable is heating-up, then it is one (or both) of its crimps to its terminals or poor connection of the terminal to the battery post or poor connection of the terminal to the body.