I need some help fixing a random stall issue with my 1984 XJS, V12.

The car will start and idle generally well and then randomly stall, no shimmy or shaking, just total loss of power/ignition. This happens either at speed on the highway or at a stop sign or normal city driving. Generally car will start after a few minutes and run normally until the next random time..

All guages register in the normal ranges, no power or heat spikes, etc.

Additionally, this is also linked (I think) to loss of battery charge, I have to keep a kill-switch on the battery otherwise something drains the battery rapidly so that the car will crank, but not turn over to start. Usually have to jump it, even after just a few minutes if the kill switch is not active.

I'd really appreciate some insight.
Thanks,
Joe

 

I would take the time and go over full electrical. Clean all ground points, plugs, relays and switches. Then go thru electrical one fuses at a time to find your short.
Wiring can be quite a pain. Take it one circuit at a time.

 

This has got to be the way to do it. If the battery is failing that fast it seems you either have an almost completely failed battery, that is giving up on the move, or something or other is using current constantly but not blowing fuses.

The standard way to find it is to measure the current being used by placing a meter between the positive terminal and the thick clamped positive cable that is normally clamped to it, and seeing what the leakage is (remember to disconnect the boot lights first).

Then remove one fuse at a time and retest each time to see which fuse, when removed, stops the leakage. If none do, then disconnect the alternator, then the starter motor, and see if that does it.

Finally, a duff ignition switch can cause intermittent feed failure to the coil, so that is always a possibility. You can eliminate this by hotwiring the coil with a fused 12v just for test purposes and seeing if the trouble goes. Also check that the connectors to the coil are properly attached to the wires, as the copper can fracture under the connector insulation - this happened to me. Also worth checking the cleanliness of the resistor pack plug (see https://www.jaguarforums.com/forum/x...sistor-134745/).
Ignition amp failure is also a possibility (nothing to do with battery failure) causing intermittent engine stops, as they can be Ok when cool, but fail when hot, then after you stop and they cool off a bit, it goes again.
Greg

 

Thank you for the tips.
I had replaced the alternator and it improved for a while, but the stall returned. So, clearly something else is draining the battery and causing the stall.... my intuition, which you (both) seemed to confirm, is that there is a faulty connection in the system someplace. I didn't get a sense that it was necessarily a major component, just some simple connection that was bleeding the battery.


Thanks.
Joe