1992 XJS V12 Does Not Start

I’ve owned my '92 XJS V12 for nearly 10 years. It has extremely low mileage (just over 10K miles) and is stored most of the time with the battery disconnected. The last time I drove it was around 2 months ago. When I went back to start it, I wasn’t entirely surprised that it didn’t crank. However, I was quite surprised that it still doesn’t crank after I put in a new battery. The dash and all the interior lamps do light up, but nothing happens when I turned the key. What could’ve happened since the last time I drove it?
In searching the archives, it appears that the fault can lie with one of 3 areas: 1) The starter relay 2) The starter itself 3) The ignition switch. I highly doubt the starter is defective given the low mileage. The ignition switch is also doubtful, since turning the key does trigger some things on the dash. As the relay, where is it on a '92? All the relays I see for sale on eBay ends in '91 model year. Any other things to look for?

More info reqd. Do/Does Headlights burn brightly? Did you give starter a “smack” (be careful of an Imperial Smack as we live in a touchy-feely world)? If headlights OK and starter bumped and still no good, roll her over at crank-pully and or have wife turn key as you check for Hot at starter.

I have a 92 also. On US passenger side of engine bay, along the side and toward the rear, is a group of three or so relays under a black plastic cover. The forward most of the group is the starter relay. Swap it around with nearby relays and see if it cranks. If it does, then replace that relay (which is now making something else not work because you swapped it around)

Can’t give you an answer as to your no start beyond what has already been given…but would recommend a battery tender be used while in storage if you have facility power available. Should help battery health and maintain memories

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One more possibility to check is the gearshift lockout “ball” switch that prevents the car from being started in any gear other than “Park”. If that switch goes out of adjustment or fails, the car will not attempt to start, even when in “Park”. The “ball” of the switch rides on the side of the gearshift lever when the car is in “Park”, completing the starter circuit to allow the starter to run when the ignition switch is in the start position. When the gearshift lever is moved to any other position, the starter electrical circuit in disabled.

XJS neutral safety switch

Haven’t done this for many years, but IIRC the ball switch is adjusted by loosening a thin locknut and turning the switch to move it closer or further from contact with the shifter lever. To test, adjust, or replace the ball switch, the shifter console fascia cover needs to be removed.

Screw the ball switch in, just contacting the shifter lever with the ball until the prongs on the switch have continuity, and only a tiny bit more; lube the ball with grease.

The shifter lever must depress that ball switch slightly to complete the starter solenoid circuit (I believe the switch needs to be active… make electrical contact… before the car will start, and my instructions below are based on that premise). It is a delicate adjustment, so make it carefully, if there is too much contact between the shift lever and the ball switch it will gouge the ball …and nobody wants a gouged ball :>)

Then, with the shifter in “Park”, disconnect the harness from that switch and use a multimeter to ensure that there is continuity between the two male connectors on the ball switch to ensure the switch is working; loosen the switch and apply just a bit of grease to lubricate the ball. Adjust (rotate) the switch using the thin locknut on the threads to lock it in place so that the switch is positioned as close to the shifter lever as it needs to be to work reliably when you use the multimeter to test for continuity, and that the shifter moves smoothly in & out of park without undue drag on the switch ball. Tighten the lock nut and re-test. If you are unable to get continuity through the ball switch, then you likely need a new switch.

You might try checking for continuity through the now-loose vehicle harness female connectors for the ball switch. I think they should show continuity through the starting system, but I’m not certain of that.

Reconnect the vehicle harness to the ball switch.

Make sure the shifter lever is in park before you test to see if the car starts

Now try starting the car with the ignition key. If that worked, then the switch is OK. If not, look elsewhere for the problem.

Re-install the console fascia cover.