Hi there,
hoping someone on here has had a similar problem and solved it without shipping their car off to the graveyard. (1997 XK8 4.0 convertible)
Left the car for far too long and jumped it with a starter pack. Managed to start it but the dash threw up a complete list of faults including battery not charging, Car ran but very poorly and was missing/shaking.
Turned it off and removed the battery. Fitted a new battery today but no dash lights and no attempt to start when turning the key. The only electrical things that work are the climate control, the radio and the red lights when you open the door. The window also drops each time you open a door but window buttons not working. Voltmeter is stuck at 17 and worryingly the tachometer is stuck at normal idle revs.
Any advice/suggestions would be much appreciated.
Many thanks,
Martin.

 

Do a hard reset first - disconnect both battery leads and hold them together for a minute or so, then reattach.

 

Did you connect the starter pack directly onto the battery poles, or to the charging pole and ground in the engine bay? From what I've gathered, if you jump the car from the engine bay pole and ground, you can fry the ECU. Hoping this is not the case!

 

I find that hard to believe and would love an expert to chime in. The positive underhood terminal is connected directly to the battery positive, (it may also connect to the alternator battery stud, too, but memory is fuzzy), and I think there is a large in-line fuse (I forget the amperage). With the exception of the fuse, it's no different than connecting a jump pack directly to the battery. All BMWs have their batteries in the trunk, too, and have underhood terminals specifically for jump start and charging.

 

I'm not an expert, but the manual does in fact tell you to use the centre of the spare wheel as ground and the battery terminal positive for positive, along with a whole host of warnings of what not to do, including this one:-

Do not run the jump start vehicle’s engine when boost
starting a Jaguar Vehicle. If the jump start vehicle’s
engine is running and the jump leads are
disconnected, damage to the Jaguar vehicle’s electrical
system will result.

This is from the S-Type vehicle care manual, but it is the same as the XK8/R:-



Sometimes it actually pays to RTFM.

 

And after that start with the basics. Check all the fuses (including the big ones in the high power protection module in the boot). Do some basic checks with a multimeter or test bulb - is there power in the fuseboxes where expected with key off and on?

The likely candidates for damage are the instrument pack (speedo etc) and of course the ECU. I would first of all check how rusty the car is underneath before buying new modules.

 

Thanks for the suggestion. Have tried the hard reset and still as was!

 

The 4.0 XK8's did not have any specific jump start requirements other than that both jump lead clamps should not be connected directly to the battery terminals. However, this is only related to the danger of sparks near a gassing battery causing an explosion and is not related to the electrical circuits.

Richard

 

Hi, Thanks for replying. I connected the booster cables to the positive terminal on the battery and the earth post behind the battery. Has worked in the past with no issues.

 

That will be fine.

If you tried to start the car with a flat battery, you will have generated a lot of fault codes. Even using the booster pack might have generated some temporary faults. As well as resetting as described above, it would also be helpful to delete all the fault codes with a cheap ODB scanner. Make sure that the new battery is fully charged and don't forget to reset the windows.

Richard

 

I believe I picked this warning up in one of the ToTheGarage "Secrets of the XK8" videos. From the other responses here, it sounds like it does not necessarily apply universally though. Either way, glad to hear OP didn't jump it this way

 

If there is an inline fuse to the underhood terminal, jump starting from it may blow that fuse. A starter may draw as much as 300 amps. You will note that starter feed B+ is generally unfused while the alternator charge cable sometimes is.

 

I see you know better than Jaguar who gave very specific instructions on how to jump start the 4.0 XK8/R to avoid damage to the electrical system. From the Vehicle Care Handbook that came with the car:-

Do not run the jump start vehicle’s engine when boost starting a Jaguar Vehicle. If the jump start vehicle’s engine is running and the jump leads are disconnected, damage to the Jaguar vehicle’s electrical system will result.

 

Seriously? The discussion in this thread is about jump starting the vehicle with a starter pack so why would I waste my time quoting phrases from my 1997 4.0 Care Manual, exactly the same car as the OP, when those phrases are entirely irrelevant. An apology for your brusque manner will be graciously received.

Richard

 

These threads are read by thousands of people for years to come, not just the OP. You are giving out incorrect information about jump starting that can lead to damage to the electrical system if someone follows your advice, rather than the instructions that came with the car.

Perhaps you don't realise that?

​​​

 

All it needed was a simple apology for your unnecessary rudeness. Do you really believe that these points have not been covered a 100 times before?
Please do not ever bother me again as I have no patience with timewasters.

Richard

 

Richard, Richard, Richard.

 

I would hope that you agree that there is absolutely no excuse for rudeness or sarcasm on these forums.

We are all here to try and help fellow Jaguar owners as best we can, so posting "I see you know better than Jaguar" as a sarcastic response to a perfectly rational and reasoned post is totally unacceptable.

Richard

 

Please take a deep breath, everyone. No need to be impatient or rude with one another.

A little time spent editing one's first draft to remove personal comments prior to posting helps keep these forums the friendliest and most informative source of correct Jaguar information.

Remember that without the benefit of tone of voice and facial expression, the written word on its own can easily seem snide, brusque, dismissive, condescending and offensive. I'm certainly not perfect, but I do try to check my own posts for these potential problems before I hit Submit Reply.

Cheers,

Don

 

Hi again, thanks for all the replies and suggestions. One more question!! The gear-lever is stuck in park and will only move back about three quarters of the way to reverse when I put a screwdriver in the release hole (foot on brake). Any suggestions?
I’m not great with electrics but have managed to check the mega fuses in the boot and all the many small fuses dotted around the car and all are intact. Think I’ll have to call out an auto electrician and hope they can work some magic! Just can’t see how the radio, climate control and gear selector light have power but nothing else.
Thanks again for any help.