1985 Series 3 XJ6 4.2L Not Start No Electrics with Key On
 

Hello Everyone.

Got another series 3 for cheap. Previous guy got fed up with the unique character of Jaguars and dumped it cheap. Score, well sort of.
Without key in nothing electric works, as if the battery was disconnected. Key in same issue, nothing electrical will work. No cranking, no headlights, no electrons where I’d like them. Checked fuses, and cleaned grounds to no avail.
Any ideas on where to start troubleshooting?

Thanks Collective Jaguar Minds
Alan

Check/clean the two "+" junction posts on the firewall. These are the "+" voltage supply points for the entire car.

If you're not familiar with them.....

On a LHD car one is a few inches below, and a few inches inboard of, the battery. The other is in the same location on the other side....below and inboard of the brake booster.

To verify, you cleaned both main grounds? One at the RH fender and the other underneath the car, RH side, about where the engine and transmission join together

Cheers
DD

first things first: Test the battery.

Battery has 12.3 volts. I applied 12v from a power supply to the Red/White wire from relay feeding the starter. The starter clicked loudly but didn’t turn engine over. Jacking it up now to check the big ground strap attached to trans and visually inspect the wiring. Update you all soon.

MMMMMM.

If 12v was applied to that White/Red relay to solenoid wire, AND, you got a "click", that is NORMAL to a minor point, and indicates that the EARTH straps are in fact earthing, or else there would be no "click",

Using a volt meter, test the battery cable AT the starter solenoid, the big sucker wire, and you should have battery voltage.

I doubt you have, or the starter would have rotated with that "click".

I reckon you got +ve supply issues somewhere in and around the battery cable connectors, as Doug has mentioned already.

I earthed the 12v going to the solenoid wire to the battery (-) post. That ground strap is not up to snuff; it’s a little bit frayed. I’m breaking that bolt free which is no easy task. Tricky to reach in by the solenoid to probe for voltage. Trying not to remove the intake manifold for access.

since apparently you have more than 1 XJ, try replacing the ignition switch from a good car in the bad one. you might have a bad ignition switch or even a disconnected ignition switch.

After time away from figuring out why no cranking, or any electrics present despite a fully charged “connected” battery, the fix was terribly simple. The Red lead from the battery connects to a electrical distribution post on the firewall adjacent to the battery. After a good look back there I noticed that the red lead wasn’t connected to that post at all. Connected it and all is back to normal.

Alan thanks for getting back with a result............glad it's running!