I am assuming a "dead car", not a dead ignition circuit.

The list will be endless, BUT, based on reading what you wrote, and my understanding of that, the battery juice aint getting to the car, agreed.

Alongside the battery there is a number of bolts/nuts, 2 or 3, forget, with the battery EARTH cables bolted under 1 of them, along with other earth cables. This is a known issue with the earlier cars, but yours is 20+ years old by now, and there may NOT be a good, or any, earth circuit via these bolts, undo them, give them a GOOD clean, and see what happens.

Check the 2 large spade terminals that are attached to the battery +ve lead, about 6" from the terminal, they have been known to pull out, fail, corrode etc, BUT, that should not give a DEAD car in my opinion, dead circuits maybe, but NOT a total black out.

Let us know what happens after the clean up, then others will have come up with ideas, I hope??.

 

i have a 2000 jag xj8 here is the issue i turn the car on in the morning i wait like 3 minutes before i run the car than soon is i start driving i saw some smoke comming out the a/c outlet so i tought the car was burning some wires anyways i turn the car off and i saw the smoke was there still so i pop the trunk and disconet the battery so the car wont burn out so than i put the battery back to see if a was more smoke there but went i have the battery back i heard the car starting up by it self with out the key also the front lights and wipers and the dash lights was on with out puting the key and the switch was off , so now i have the battery disconect and if i connect the battery i see fron lightd, dash lights and wipers on ,im wonder if somebody has any idea about this weard electrical problem on this xj8 ,,,,,,,,