[v12-engine] six pack coil routing

Does anyone know how the output sparkplug wiring
from the dual six pack coils on a 95MY XJ12(x300)
are wired to the plugs? I know the firing order but
cant figure out the six packs.
I’ve seached from Kirbert’s book to the archives
and even purchased the Alldata online reference
(ending up with a lousy drawing).
Please Help. I know im missfiring. Ill even promise
not to drink that case of beer next time. Cross my
Playtex and hope to die… Honest.

                   Thank You  Gary

95Xj12
88Xj6
various toys__________________________________________________
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gary losito wrote:

Does anyone know how the output sparkplug wiring
from the dual six pack coils on a 95MY XJ12(x300)
are wired to the plugs? I know the firing order but
cant figure out the six packs.
I’ve seached from Kirbert’s book…

…and the reason you didn’t find anything is because I barely know
the thing exists! It’s been mentioned but not discussed, at least
not while I was present on this list.

to the archives
and even purchased the Alldata online reference
(ending up with a lousy drawing).

Could you please e-mail me a copy of the lousy drawing?

Please Help. I know im missfiring.

I know the concepts behind distributorless ignition, and I’m a pretty
smart guy. I’ll try to help, but I’m going to need more to work
with. How do you know you’re misfiring? What have you checked so
far? Why do you suspect there’s an issue with the spark plug wiring?

You might also look around under the hood and see what you can learn
from labels and stickers. On my '83, for example, the spark plug
wiring was clearly shown on a sticker on one of the air filter
covers.

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In reply to a message from gary losito sent Thu 29 Jun 2006:

Gary:
One of the advantages of your 95 car is that it is an OBDII
equipped. If you have a missfire, a code reader should tell you
specifically the cylinder(s). With this info, you will save a lot
of money on replacement parts. You don’t have many things that can
go wrong in comparison to your 88.–
The original message included these comments:

Does anyone know how the output sparkplug wiring
from the dual six pack coils on a 95MY XJ12(x300)
are wired to the plugs? I know the firing order but
cant figure out the six packs.
I’ve seached from Kirbert’s book to the archives
Please Help. I know im missfiring. Ill even promise
not to drink that case of beer next time. Cross my
Playtex and hope to die… Honest.


uncle
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Yes, I purchased an OBDII/CAN scan tool just after
the initial symptoms appeared. ie: rough idle (that
is; the normal oscillations of the engine as it waves
left to right ever so slightly were interrupted by a
flat spot or two). And hesitation, but most of all
loud “popping” ( PUUMPTFFt)of the unburned fuel and
air mixture as it ignited upon contact with the hot
exaust catalist. This occurring whenever the pedal was
decidedly pressed. Unfortunatly all the scan tool
could do was to Verify “Missfire right bank” and
“Missfire left bank”.(JOY!).__________________________________________________
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Just a quick insert to say…
Thank you one, and all for helping me with
my mess up. And a Special Thank You to
Mr.Bywater,Roger of aj6engineering for his
suggestion. Next time I tackle this, it’ll be just a
six pack
and not a case. Honest injun.
Gary
95Xj12
88Xj6__________________________________________________
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Hi all -
Rather than create a new post on the same topic, I’m resurrecting this thread from a few years ago. In short, I’m looking for the spark plug wiring diagram for the Nippon Denso distributor-less ignition system. If someone has a picture/scan of the diagram, or can reference their own properly plug-wired engine, I’d appreciate the information.

Furthermore, if there are any 6.0L-specific reference materials, I’d love to know about them. I have the XJ-S ROM with the supplemental information about the 6.0L, but clearly it does not cover the (XJ12-only?) distributor-less ignition system from the final incarnation of the V12.

For the more curious (or those looking to waste some time), I’ve outlined my spark plug wiring conundrum, below.

As posted else where in these forumns, I’m in the midst of working on a 1994 6.0L – one of the model years with the gutless Marelli distributor. I have removed the OE 1994 top cover & distributor and replaced it with the later top cover for the distributor-less Nippon Denso (aka ‘Nippondenso’ or ‘Denso’) ignition system and I have bolted down 2 OE-style Delphi coils.
Each ‘six pack’ coil contains three double-ended coils, meaning that 2 spark plugs are ignited simultaneously: One spark plug which is igniting fuel and air as a given cylinder approaches TDC on the compression stroke (just before beginning the power stroke); one spark plug in a cylinder that is (in the case of a Jaguar V12 and many other engines) operating 360-crankshaft degrees apart and approaching TDC on the exhaust stroke.

To the best of my knowledge, the firing order for all road-going variants of the Jaguar V12 is:
1A, 6B, 5A, 2B, 3A, 4B, 6A, 1B, 2A, 5B, 4A, 3B
Anyone know if that is not the case?

Therefore, the cylinder pairs that are 360-crankshaft degrees out of phase with one another (where one cylinder is on compression stroke and the paired cylinder is on exhaust stroke) are: 1A & 6A | 6B & 1B | 5A & 2A | 2B & 5B | 3A & 4A | 4B & 3B
Does that seem right to those of you still following along?

If so, then I believe that those would be the cylinder pairs that should be wired to a common double-end coil.

So here is where the plot thickens: A few weeks ago, I acquired another 6.0L V12. This engine is a MY1995 from an XJ12. It has the Nippon Denso distributor-less ignition from the factory, so I decided to compare the pairs that I believe are correct (above) to the paired cylinder on the engine I just bought.

The picture below illustrates how the spark plugs are paired on the engine as I received it.


As highlighted with the orange ovals that are superimposed on top of the coils, there are 2 cylinders that seem mis-wired to me. From the pairs that I outlined above, I expected that the A Bank would use one coil and the B Bank would use the other coil. For the most part, this holds, but them there are two spark plugs/cylinders that – at least as I received this salvage motor – do not follow that pattern. While the two plugs that seem to be swapped aren’t close to one another in the firing order (4B is 6th and 4A is 11th), they would have a spark plug igniting adjacent to one another in a wasted spark configuration…right?

Is the 1995 engine that I recently acquired just wired up wrong? That is entirely possible on an engine with an unknown history. An obvious check would be to pull the plugs and see how gunked up they all are, especially 4B and 4A. (I’ll do that when I am by the 1995 engine again as it is not currently at my home shop.)

Or, have I overlooking something where this pairing makes sense? (Truth be told, this isn’t unlikely, either.)

As always, I look forward to everyone’s input.
All the best to this forum community!

Your original wasted spark pairing assumption is correct and the picture is wired up wrongly as you surmised.

kind regards
Marek

pix of engine vee, coils inIMG .

Your original wasted spark pairing assumption is correct and the picture is wired up wrongly as you surmised.

Thank you, Marek!

Ronbros - That looks like a very nice setup. Are the coils adapted to your engine from something else? Or is that yet another variant, like the TWR JaguarSport 6-liter? In any event, very nice!

Hi Gary,

BTDT. Maybe this will help.X300 Ignition Layout from 801S - 2000.pdf (41.6 KB) :slightly_smiling_face: