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So reading a 'book' called 'Experience in a book' by Kirby Palm on all the potential issues / gorcha's and pitfalls of the XJS and I got to a section that discusses ignition systems, this text is on page 125
Possibly the worst area for heat problems is within the “V” on top of the engine. Early XJ-S’s had so much trouble with cooking the ignition amp that Jaguar created a relocation kit to move it out of this area.
It doesn't clearly state what it means by 'Early', nor does it expand on the relocation kit mentioned. I have the CEI ignition and the AB14 amp mounted on the top of B bank manifold. Since the wiring between it and the distributor is damaged I was considering moving it - I could simply replace the little piece of harness and the sensor int he distributor and leave it where it is, or I can fix the wire, or I can relocate - except screened cable in Silicon isn't that easy to find (for those wondering why the commonly used cable - PVC - is not suitable for prolonged use above 70°C).
The same document also discuss's replacing the vacuum advance every couple of years, again this is due to the potential for heat damage.
Anyone here have any experience moving the ignition amp - is it even worth doing for cars with it mounted on the manifold ?
What are the thoughts re the vacuum advance module ?
Marelli cars (88-96) moved the amps to the front of the rad behind the ac dryer to get them nice cold air, and fitted a crude heat transfer plate. If redoing things moving an item to a cooler location would sure reduce wear.
They are meaning the OPUS system on early cars, which was mounted in the center of the V.
I have taken temperature measurements of various locations in the engine bay and where the AB14 is located is actually the coolest spot. It has all of the intake air running through the manifold, so makes for a very effective heat sink.
It has all of the intake air running through the manifold, so makes for a very effective heat sink
Never thought of that - makes sense now you mention it - I did wonder what they were thinking to locate it there, think I'll leave it there and fix the wires.
They are meaning the OPUS system on early cars, which was mounted in the center of the V.
I have taken temperature measurements of various locations in the engine bay and where the AB14 is located is actually the coolest spot. It has all of the intake air running through the manifold, so makes for a very effective heat sink.
Ya, he wondered about moving it - newer cars moved it to the rad area which is nice and cool compared to inside engine
All my AB14 were remounted, by me, out the front of the radiator, alongside the Aux Ign Coil. 25 years now, never had anymore heat related issues.
When you return from a drive of 1 hour or more, pop the bonnet and "feel": that I let manifold, and the AB14, the burn marks could be interesting. I am yet to be convinced that OE placement is AB14 friendly. OK for the warranty period, thats it.
I had mine in the OEM location for years and it was new when I bought the car. It failed after about 10 years. I put mine out in the airflow on Grant's advice. Important to seal it carefully though in rainy europe.
It is mounted on stilts so air gets all round. Important to add a dedicated earth, which is why the top of the casing is sanded to bare metal by one of the fixing studs.
Also, it is worth understanding that the amplifier generates far more heat at tickover/low traffic speeds, than when blasting along the motorway. It is the traffic work that kills them, as they have to dissipate far more heat (for reasons that someone explained on here that I have forgotten) from low revs work than from high. And of course, it as at low speeds that everything heats up under the bonnet.
Last edited by Greg in France; Sep 8, 2020 at 01:22 AM.
On 4 of them, NO. I picked up the shielded wire inner core inside the body aperture in front of the RH door hinges. That wire was soft and pliable in there, simple attachment, and heat shrink sealed, just in case.
The other 5, I used standard TV antenna Coax, and spliced it in at the same point. The owners wanted it that way, and I had no issues, their car, their $$.
Black (colour means zero, just what I had) RTV was used as a seal all around as Greg stated, and the plugs also. Earth wire is MANDATORY.
So this is just thoughts - since the amplifier itself is largely connected in two places (except for the screen) , those places being the coil and the distributor is there any reason why the amplifier coil connections cannot be made at the remote coil - the circuit is essentially the same but it is connected in a different location - it seems pointless to run the wires all the way back which would mean 4 wires not two heading to the primary coil - just trying to picture this and how to make it work in the cleanest manner possible.
Last edited by BenKenobi; Sep 8, 2020 at 01:03 PM.
In my own case, I carry a spare amplifier. In the event of needing it, I can disconnect the OEM plugs in the OEM location, and connect the spare amp in its OEM position and be away. Just leaving my extended loom where it is. If you did what you suggest (assuming it would work, but I have no idea whether it would or not) this would not be possible.
As the aux coil has leads going to it from the main coil, and as the other two amp leads need to be all the way back to the dizzy, is it worth the bother of changing the system? just my thoughts...
I plan to retain all the OEM plugs as far as the amplifier itself goes. The only lead I need to run is the distributor one if I wire it as above, the cables between the two coils are already there and don't seem too bad but I will be relocating them higher up out of the valley, I am already replacing the injector harness completely, I guess some part of this is the OCD in me and an intolerance of breakdowns, especially those that can be prevented by appropriate maintenance.
I think that I owe it to the amplifier to give it the best chance of survival. Pretty soon getting spares won't be so easy, I'm already on the constant hunt for numerous other 'essentials' to put on the shelf that are now flagged as 'no longer available' although getting this car back up to a standard I can live with isn't the cheapest thing I've ever done.
I deleted that 2nd coil on ALL the cars at the same time as the relocation.
BUT
I see no reason it wont work, I will wait for your answer when you have done it. Red to Red, Black to Black, flick the switch and stand right back. Its only voltage when all is said and done.
Ben
Yes, Grant's excellent point about doing the Jaguar single coil mod would mean two fewer wires to the front. When the V12 was made, there were no coils that had a sufficient recovery time to run the V12 above about 3500 rpm, hence the twin coils. Now there are such coils and Jaguar fitted them to later cars.
Guess I need to read some more - I missed this single coil mod - where is that explained
I did a little read but it still isn't very clear (ended up in some rant about California smog rules - justifiiably but I ain't firing that up again) if I replace both coils and place a single DAC6093 in place of the coil by the throttle pedestal this is all that is needed and the system becomes single coil.
if I replace both coils and place a single DAC6093 in place of the coil by the throttle pedestal this is all that is needed and the system becomes single coil.
Lucas CEI amplifier
