'86 XJ6 Progress!
 

Well, now we may be getting somewhere. After changing the coolant this afternoon, I rigged a wire from the + battery to the + coil. I left every connection in place on the coil + post, and just added the wire.
At first I could not tell any difference. I removed the wire from the battery post and drive 15 miles, stopped at a buddy's repair shop and hung out a few minutes. When I got ready to go, I connected the wire and fired up, the car ran crummy. I think maybe because the gas got hot in the plumbing (remember, too: my air conditioning is out so there is no fuel cooler). I took the wire loose and drove home. It ran down the road perfectly but died at almost every intersection. I learned to keep my foot on the gas a little and take it out of gear at a stop, and it still died sometime when I put it back in drive. When I turned in my drive it died and I coasted to a stop. It started right back, though. I stopped it, got out, and reconnected the wire, then closed the bonnet and started her up. She idled fine, I put it in reverse, the idle came down to about 700 and held steady when in gear. I backed out, drove down the road, and it did not die. I stopped, turned around, and it did not die. I drove back in my drive and it did not die. After I stopped I let it idle some, then put it in reverse several times, and it did not die. I let it idle, got out and took the wire off the battery post, got back in, put it in reverse, and it died.
I realize putting 12v to the coil terminal is bypassing the ballast resistor; is this the reason it's not dying: increased ignition power; or is something else wrong? Ignition switch? Ballast resistor? wiring?
I tired letting it idle while connecting and disconnecting the wire: it may be that the idle speed increased a tad and it got smoother with the 12V to the coil, but this may be my imagination.

Okay, sounds like 12v directly to the coil improves things.

Correct, with the jumper installed you've bypassed both the ignition switch and the resistor.

So.....either the ballast is on the fritz (not unusual) or the ballast is not getting enough voltage from the ignition switch.


I'd take the ballast off and jumper/configure the solid white wires so they are attached directly to the coil "+" post and then drive the car again....but without the jumper wire from the battery "+" post.

If the good running behavior continues then throw the ballast in the trash (more than a few have ended up there) and attach the white wires permanently to the coil "+" post.

If the good runnng behavior does not continue then you have a problem with the igntion switch (common) or a problem with the white wire from the ignition switch.

Cheers
DD