Hello Michael, and hello to all, been a while to say the least...
Make a list of everything you need as far as diagnostic specs, etc, I'll look them up tonight.
I just bought an '87 XJ6 VDP, had the exact symptoms you are having... looking at the coil and ballast confused (and distracted me away from the fuel starvation issue, or air/fuel issue)that was the culprit all along.. Unless you re-wired the engine bay, simplify this a bit.
IS THE CAR STARVING FOR FUEL??
To check this, pull the hose (the main hose going into the injector rail). If you have someone crank the engine, collect fuel hopefully (my guess is you will) into a jar until clear, then re-install, you've basically ruled out the bad gas/bad pump issue, but stay on the same tank to be safe. If it has not been driven for months and parked outside, pick a tank, drain it, and then fill it back to about half-full (or half-empty, but let's be optimistic).
Now, if you received and collected a bit of milky/rusty (or both) gas in the jar at the main F.I. line into the injector rail, consider your fuel filter, the trunk-mounted, alloy cannister, Trashed! Once water (or moisture even at its lower level creeps into the filter, the car will usually experience a bit of a fuel starvation issue. The water stays as intended in the filter, but it also blocks the good fuel, water being heavier chemically than gasoline. Replace it. I think I picked up a FRAM or Bosch Filter at AutoZone for around $17.00. You may even prefer, as I did until I got to "know the car" pick up a few cheap clear inline Fuel Filters, just to keep an eye on the flow. It also is a great way to backtrack in your diagnostics endeavour later to keep an eye out for a pinhole in the fuel system that is often overlooked the minute clean gas is reaching the injection rail. The plastic inline fuel filter is a personal choice, but it made me feel more in control and less like I was repeating the same steps over and over (chasing every possible issue, back and forth during no-start condition diagnosis, then questioning whether or not I should start over and tear down this or that again..). The fuel pump is simple to rule out (kinda...) You can start and run an '85-'87, providing all else is cooperating, on 35 PSI, probably less, but that's about the magic number. I've never checked PSI on an XJ Fuel pump, they usually are alive and pumping or dead, and it's not hard to tell the difference.
Have a friend hold their hand on the pump as you crank the engine (is the pump vibrating and showing signs of life while the key is being turned? It's probably ok at this point if you hear the "Hummm" and feel the Pump Vibrating slightly (as the car is being turned over with a key (trying to start the car, or while the car is running of course).
If you wonder as I did whether I felt body vibration or fuel pump activity (the not-trusting-my-senses issues that plagued me for two weeks this past May), then just unplug the Pos. or Neg. wire to the fuel pump. You'll feel alot less vibration and hum, and I think (without pulling the line and doing a fuel pressure check, you can move on, hook it back up and now get to the engine bay again, where you have to take a deep breath and say to yourself that you need to forget about all the usual suspects (In other words, to keep my sanity, I had to quit digging for that one little thing that I missed, such as a ballast wiring reversal, which I don't think is possible anyway, but that's how I was approaching this no-start condition.
Do you know the major electrics, beyond a doubt, have not been redone completely? No new harness installed, no new Computer installed, etc? If you know that this isn't the case, at best, pull the plugs, clean and gap them, do one last check on plug wire order (firing order) and then have a friend around again, with a can of starting fluid in hand. Don't use it to run the car, but make the car run with it if possible. BTW- Have your battery fully-charged and ready for alot of cranking, maybe 20 minutes or more, stopping every 20 or so seconds maximum to avoid (try to avoid anyway) burning out your starter.
The idea is to warm up the engine by consistent and continual cranking. This will get the Cold-Start (choke issue) Injector ruled out as the culprit if all continues as it did with my car.
If we know at this point that you received clean gas to the engine bay, there hasn't been a wiring restoration that may have gone horribly wrong, just a valve job unless I missed something, then the no-start probably is being caused by a bad fuel/emmissions component under the hood. If a friend spraying starter fluid into the trumpet-like hole at the beginning of the air intake makes the car run, until he quits spraying, even for a second or two, then fuel starvation/poor air-fuel mixture is more likely the issue.
Just to be sure that no fire occurs, try to have the friend who is spraying the ether/starting fluid run the car on it as you rev and work the gas pedal (your car is warming up at this point), then let the car almost die, letting the vapors leave the induction system, then spray rather heavily again and work the gas pedal, keeping the car running.
If you get this far, then you most likely have the same problem that I had. The MAF Unit was the sole culprit. The visual test (the tilt of the flap, and I can't remember what else, not appearing scorched inside I assume) checked out fine on my car, I skipped the complicated (at least I assumed it pointless and too complicated to pinpoint a bad Mass Air Flow Meter, and dismissed it as highly unlikely it just "died", therefore I moved on...) thoughts of testing of the MAF Unit itself bounced back and forth for another week in the back of my mind, but the MAF Unit "looked fine", and I wasn't about to waste time testing something else, only to further my frustration to the point of giving up on the car.
Sorry I'm rambling, long few days here, exhausted, but that's another story..
Let me tell you what happened in my case, do the above first but watch out for build-up of fumes while trying to "warm" the engine by keeping it running with ether. They can and do ignite, keep something (fire extinguisher and hose around while doing the warming up.
1) If you can keep the car "running" with a friend flooding the intake with starting fluid, try to do it long enough to warm the engine up a bit. This helped me to get around some questions about the Cold Start Injector/ Thermotime possibility issue that was nagging at me. If you "run the car" like this for a bit, the temp guage gets fairly close to operating level, then you more than likely just eliminated an ignition wiring mishap or a hidden, cracked wire as the cause of no-start, as well as got the car to skip over the cold-start question. If the car during this procedure continually wants to die as if it is waiting for the "spraying of the starting fluid" to stop so it can quit, has very little or no throttle while running on the starting fluid, then you are still experiencing exactly what I was experiencing.
2) Take a quick step out from behind the wheel, or have a third person ready, or let the sprayer of the fluid stop providing your "fuel" long enough to do this:
Disconnect the plug/harness from the MAF Unit.
(remove the retaining wire that surrounds the harness connector first, preferrably prior to getting the car warmed up). If your MAF is the culprit, you will immediately notice that you gain significantly in throttle reaction, less starting fluid is required to keep the engine running (or none at all) and the idle will jump up, in my car it hovered around 1600 to 1800 RPM. My car usually idled on its own for a few minutes at most, then died, but started again with a small spray of "ether/starting fluid" and ran for a minute or two more at high idle, on its own, then died again. Plug the MAF back in, that is if you are still with me and your XJ6 is behaving as mine was, and you will be back to the continual spraying to keep the engine running, and almost no throttle response at all, I think I mentioned above.
3) If you have the same results (as I laid out above) with your car, immediately swap out the MAF. You should be fine, not perfectly tuned since the MAF unit has to adjust to the car. Leaving the battery disconnected for 24 hours is what I was told to do to allow the computer to "reset" and to allow your car to "accept" the replaced MAF Unit. I did have to adjust the idle and tinker some to get it to what I considered to be a finely-tuned state, but the moment the new MAF (used, actually, $35 ebay purchase) was installed, the car idled on its own, didn't die and sputter as it had been doing the prior 3 weeks as I drove myself half-batty checking and re-checking the fuel pump, the ignition wiring, draining the tank and checking for clean fuel at the injector rail, etc.
4) This is important, or potentially a disaster-averting footnote anyway..
When I began working on the car, the MAF bellows hose to the throttle elbow was loose, the straight black rubber connector to the throttle assembly was not fitted well, but this turned out to be a blessing. It also told me that the prior owner almost had the "no-start" condition pegged and tracked to the MAF Unit... ;(
When the fumes from the repeated early attempts to start the car built up inside those areas (from the throttle, through the MAF unit, and into the air filter housing assembly) and a small backfire occurred not having the clamps completely and tightly secured may have saved me from a major engine fire. When you are using the starting fluid (even actually also when not I have since been told) during attempts to start a car which may be starving for fuel or have a fuel/air mixture failure, the fumes remain trapped inside the air intake and the exhaust port areas. The two or three times a backfire did happen, I quickly knocked the ribbed bellow hose loose and removed it as well as the rubber MAF to Throttle Connector loose, watched the ether burn off, then slowed the pace a bit a left some air gaps at those connections for easy access to extinguish a fire should it have erupted. It came close once, but I believe that the "flames" were the wet ether burning off, which is a fire, but much easier to extinguish than a piece of burning rubber, electrical wiring fires, etc..
5) I am not certain that warming up the car by supplying its fuel from a starting fluid nozzle was even necessary. That I guess was my way of totally ruling out the Cold-Start Injector as the cause of the no-start condition, even if my understanding of that diagnostic procedure was incorrect. You could and should just have a friend spray some starting fluid through the air intake, possibly just remove the entire air cleaner unit while doing this (someone else please chime in here, but I wish I had done so in retrospect, so does my crispy air filter which is now in the trash). Leaving yourself and the car a "quick release" for the two connectors by not tightening the clamps down won't hurt anything. Both of the hoses almost have to be forced into place anyway during normal installation. If you fully tighten and assemble this area, and a backfire sparked an internal flame, you would be forced to stop and unscrew the clamps to put out the flames. (On both of these air hoses I left the clamps very loose, both connect to the MAF UNIT, one is ribbed/accordian type, the other straight rubber tubing.) Another word on this, the backfire can potentially blow them 20 feet into the air. This happened to me recently while using starting fluid after running out of gas. I had the tank switch on the wrong setting (the RH tank was empty or contaminated), but not paying attention to which tank I was using, kept yelling for more starting fluid, convinced I was going to fire the car up at any moment. Then the backfire came and the intake parts that blew out of the engine bay landed about 40 feet from the car.
ANOTHER QUICK THOUGHT:
Before you embark on more hardcore diagnostics, have you checked inside the passenger door to be sure that the inertia (fuel-cutout) switch did not trip to the cut-out mode? I'll have to look at mine later today, but I believe it should be pulled UP completely. Again, Exotexs, Larry, Steve, anyone, corrections may be needed here, but I think I would just rule that out before breaking a sweat on whatever you decide to do next.
Sorry about the several confusing sentences above, I'll get some rest and edit mistakes later, but I hope this gives you an idea of what I went through (90% of my effort was spent chasing electrical shorts, major issues that could cause all of the same symptoms, but pulling one plug solved the mystery and restored what was left of my sanity (and trust me, Jaguar diagnostics will eat up sanity very quickly...) Hope I get a reply saying your car has been running for weeks now.. Best Regards,
Brian
Hey there Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
A friendly reminder - be careful what links you click on here. If a link is posted by someone you don't know, or the URL looks fishy, DON'T CLICK. Spammers sometimes post links that lead to sites that can infect your computer, so be mindful what you click.