No I don’t. Never had one - what I linked to describes the wiring with one.
The two white plugs are from the ignition amplifier. All my wires are black up to the junction with the harness which is why I hope I have a picture.
Janson,
There are no black wires to the the coil in the original Jaguar wiring. The wiring in David’s picture must have been repaired or modified. Attached is a picture of the right side of the engine in my former 1984 XJ6 Vanden Plas. It did not have a ballast resistor.
I don’t have my notebook handy so I can’t say off the top of my head what the wires are, but I believe they are White, White-Black, and White-Slate-Blue. Let me know if you need that wiring detail and I can provide that tomorrow.
Paul
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sorry, i misunderstood.
the other harnesses are pretty crispy. but if they’d help you as a template to remake one you can have them.
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The ignition circuit is specific to ignition only, Janson;
White wire from ign key to coil ‘+’ - check for power with ign ‘on’ and in ‘crank’. One back-up is to jumpwire battery ‘+’ to coil ‘+’
The white wire from ign amp connects likewise to coil ‘+’ both coil and amplifier is thus powered by the white wire from ign key.
The black/white wire from ign amp connects to coil ‘-’, grounding the coil ‘-’ through the ign amp to ‘charge’ the coil. Ignition, plugs sparking, occurs as ign amp breaks coil ground…
The two-wire connection between the distributor and the ign amplifier conveys the weak signal, generated by the pick-up in the distributor, to the ign amp. Which amplifies the signal (hence the name) to be used to make and break coil ground…
As said, the ignition is self contained and independent of other circuits. With parts working correctly and correctly connected; use a spare spark plug, triple gapped, connected to any plug lead to verify spark while cranking…
There are two other wires connected to coil ‘-’; one white/black to the ECU to trigger injection and one white/slate blue connected to the revolution counter. They do not interfere with ignition - unless shorted to ground. They may be disconnected for specific testing of the ignition…
Frank
xj6 85 Sov Europe (UK/NZ)
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Wow. The dreaded PO strikes again!
Waaaay back in the early 80’s, I bought a 1973 Triumph GT6 MkIII. One day I was driving it to work, and just as I pulled into a parking space and straightened the wheel out, the steering locked up and the engine died. Come to find out that the dreaded PO had decided he didn’t like one of the warning buzzers behind the dash somewhere, so with the buzzer buzzing he went under the dash with a pair of dykes and started clipping wires at random until the #$%^& thing quit buzzing. He then stripped wires and twisted them back together and wrapped each splice with a strip of electrical tape. The resulting rat’s nest of bad connections got caught around a joint in the steering column, pulled tight, and yanked a couple of wires loose.
Honestly, yours might look worse.
I’ve three points:
-
Look carefully at the end of the coil. I see what appear to be two cracks. If that is true, volts can run along them and mystify most of us.
-
Rely on the S57 jaguar schematic. ID real Jaguar wires by color code. .ID Lawn mower stuff and dump it.
-
Kirby, my PO did it neater. When I replaced the ignition switch in my lump, I found that the buzzer was connected to it in a piggy back manner. Original Jaguar wires!! The buzzer was dangling free. I was lucky, it caused no mayhem. I considered. whacking it. No, best just hook it up out of the way,. It now buzzes, but, as I am hearing impaired, no big deal.
Any original Jaguars around to inspect and relate to. Even one in the junk yard might help!! …
Carl
This was quite the topic on another thread (which I can’t find right now) to have or have not a ballast resister. I think it was “yet another XJ that won’t start”
One of my XJ’s had a ballast resister, and the other didn’t both got MSD coil and amplifer upgrades so I ditched the resister. Just a heads up, of you do like I did and swap out the coil for a big red one, it doesn’t fit in the bracked. It’s too fat oh sorry thick. or sorry. the circumference is larger than the stock coil and the bracket won’t fit around it.
Rabbit Hole!
I took a piece of masking tape and covered the stock coil bracket to make a template. then added I think about an inch to the over all length; bent the aluminum flat stock around a pipe, drilled the appropriate holes and cut out the end for the big Phillips head bolt and slid the coil in place. Looks like it should. Other than being red, and reading MSD Flame thrower (who comes up with these names anyway)…
Back on Topic
When I first got my green XJ6 it didn’t run and I replaced the coil with one that I had kicking around. The car fired right up. However, after driving it a bit and things got warmed up; the car was hard starting. If I waited long enough, then it would start. I got fed up, and ran across the street to an autoparts store that just happened to be a speed shop. the only coil they had was the MSD which did not come with a resister. I replaced the coil and ditched the resister and never had an issue after that.
I was so pleased with the end result, I applied the same configuration to the '86 XJ6. Along with the ignition amplifier.
According to the Jaguar training material, the ballast is supposed to help with cold start conditions. Frank will disagree; and I"m on the fence. The ballast maintains a constant battery voltage minus - 1 volt to the coil. According to the training material, the Ballast is supposed to maintain a consistent to the coil with out any fluctuation which may happen upon engaging the starter. (heads lights dim when starting a car). the ballast is supposed to minimize that from happening to at the ignition side.
But again, I’m sure I’ll get put in my place - or as my old Boss would stamp my reports with a bit red stamp reading “Wrong Again!”
So, if you’ve got a good solid battery, then ditch the ballast, or try running with and without, and provide your feed back to the forum.
Sorry long winded.
I have two XJ’s and two brand new Ballast resisters that haven’t found themselves installed yet. I’m going to do a test to see if there is any reason to have a ballast resister.
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I’d like to see that training material, Mark…
Basically, a resistor is a current limiter, and the current through a resistor varies with voltage - the higher the voltage the higher the current. And the higher resistance in a resistor, the lower the current…
The coil is a transformer, changing the ‘12V’ battery voltage to the high voltage required for sparking. Crudely; voltage makes the arc - the current provides the energy for the spark to ignite the mixture…
There is not much ‘constant’ in voltage and current flow…
Frank
xj6 85 Sov Europe (UK/NZ)
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Mark, now I am curious. What exactly is the coil and, more intriguingly, the ignition amplifier you are using? Still with the original distributor?
Thanks
David
I cover the ignition amplifier in my Jag Mod video, “How to put the spark back in your Jag” then the tune up covered in “XJ6 Tune Ignition up”
The coil that I used is the MSD part number 8202
There are several 12V canister style coil offered, some with balasts and some without. I haven’t reviewed the specs to see if there’s any differenece.
Without reading the specs, I’m going to assume that the differences between coils is the resistance of the primary winding (wire diameter and number of windings) and the same goes with the secondary winding. The secondary winding is what provides the spark. more windings hotter spark.
The ignition amplifier is an MSD part number 5596
Yes I am using the stock electronic distributor.
Mark:
The ballast resistor was not only used in Jaguars. it was also found in USA cars. but, that was in the day of point and condenser ignition,.
The need for it left with that system. Oddly, it apparently lingered on in some of the XJ cars. ditching it, a common practice.
Intuitievely to me, more volts is hjotter spark Hotter spark is good the converse is true. so, why convert bvolts to heat to dissioate???
Carl.
I know this. I remember finding these in the older points systems in a couple of the older vehicles I worked on at the Chev Dealership as well in auto shop. I assumed it was to keep from frying the points.
Right !!!
Carl 
I’ve got the same thing going on with my '86 and '74 XJ6. at this stage of the game the it’s not broken (totally) so I’m going to address the wires when I have to. Hopefully it won’t be on the side of the road in the pouring down rain in the middle of nowhere.
I completed wall to wall engine bay restorations of a 1987 XJ6 VdP and a 1984 XJ6 VdP as well a completely stripping three Series III XJ6 parts cars and the wiring harnesses in all of them were badly damaged by heat and engine bay fluids. Some of the wiring was so brittle that I could snap the wires in two with my fingers like a twig. I rebuilt some of the original harnesses using the best bits from my parts cars including connectors and the original colored wires from elsewhere like inside the dash. It was a lot of work to clean, measure, cut, solder, shrink wrap, and tape the rebuilt harnesses, but they looked like new OEM harnesses when I was finished with them. The harnesses beneath the intake manifold that went over to the Air Pump and A/C compressor were usually in the worst shape.
Paul
Where is the ECU located on the 87 xj6
In the boot, upper right corner. remove a trim piece to reveal it and the bulf failure unit…
Mine Is gone. wet to texas to help a car in distress…
carl
Well, that’s one way to look at it. They design the coil to operate at about 6V so it’ll put out full voltage when starting, then apply a ballast resistor to keep it from overheating whenever you’re not on the starter.
Sorta. The problem with points is that it’s possible to have the ignition on with the engine not turning and the points closed, so there would be 12V applied continuously to the coil. It’d burn up pretty quickly. Once you go to electronic ignitions, it’s pretty easy to ensure that power is only intermittently applied to the coil – but that didn’t mean all of them provided such assurance.
In particular, the Opus ignition on the early Jaguar V12 still involves a ballast resistor. As is typical for a ballast resistor, it’s supposed to be bypassed when the starter is engaged. This involves a couple of dedicated contacts in the starter relay. The starter relay retained those contacts long after the ballast resistor went away with the Lucas CEI ignition.