While waiting for the weather to cool down before I tear into much needed work on my XJS, I thought I would see why I get inconsistencies in starting. Battery is good, but now and then I just fiddle with wires around coil, and distributor and it starts.
After reading recent events on this forum, I got brave and pulled the HT on the coil and you can see the results. Cracked and wires are nearly broken and loose. When THEY put new plugs and wires on they did not report this to me.
Think I need a new coil?
In second picture a question. Is that the other coil?
Any advice would be helpful. Learning piece by piece, as I will not give the shop 30K to fix everything.
Yes the second picture is the second coil.
That first coil looks like it should be replaced just from where the distributor wire connection point is , since the insulation plastic looks broken. Simple fix would be to replace the pair of them with one(which I just did last week) part #DAC 6093.
Thank youā¦yes I will.
The white wires need replacing, connectors are looseā¦but not sure how to do thatā¦so maybe splice in new connectors?
Is that a soldering fix, or splice and tape. Really new at this.
When I get the injectors and hoses off maybe I could re wire all of those.
These are half the size. Are they the ānewā thing rather than the slender taller old style?
Just looking at your pictures, your fuel injector hoses look concave in the middle which means theyāre old and dry probably original. Your injector plate and screws look corroded, which suggests theyāve never been off or serviced. Your injector wiring harness probably needs replacement or rebuilding. (Ask me how I know) Your car is the same year is mine. You should probably take a look at your amplifier module while your at it and replace. I just did that recently. The coil connection wires I just cut off the connectors and replaced with new compression fit ones, and shrink wrapped the wires at the connection point so you donāt have any exposed frayed wires. Thereās even a liquid wire shrink wrap that you can dab on and rubberizes when it sets.
I think you would notice a difference in the way your car runs after these few items.
They are epoxy filled rather than oil filled, which was a recommended Jaguar replacement part as it could do the job of the two old style at higher RPMS
Well, no, the performance is unchanged. The bottle style coils were designed in an era of points and condensers, and there was always the possibility that somebody would leave the ignition on with the engine stopped with the points closed. The unlimited current would quickly burn up a coil, so the coils were massive and oil-cooled to minimize that problem. Once the world went to electronic ignition systems, the electronics were designed to prevent such unlimited current situations regardless what the car owner did, so the coils no longer needed such measures to avoid burnout. And the coils could go to lower primary impedance as well, giving better high RPM performance. All this means that a single, compact 0.6-ohm coil wasnāt available when the V12 was introduced but became common a few years later. Performance is unchanged except for the reduction of a couple of pounds of weight.
Good info.
This fall I will replace the entire fuel rail. Sending it out. Amp module I can do and will.
Will give the connector replacement a try, and get the new coils
Thank you Jagrr881
Thanks Kirbert.
So I could just replace one, and take the other (front one) off? I think you mentioned that somewhere, maybe The Book.
I was always of the impression the secondary coil was energized when the V-12 was running at higher RPMās , as the primary one would not keep up with the spark plug firing intervals.
Not a performance upgrade, just that the newer type eliminates the need for a secondary coil.
Or I guess the secondary coil was blanked off and run in parallel to increase the power of the primary coil based on the amount of pulses required for a V-12 engine? ( did I get that right?)
Thereās no switch in there. The secondary coil is permanently wired in parallel with the primary coil, even when the engine is off.
The primary impedance of an ignition coil is essentially a measure of how long it takes to build up spark energy when 12V is applied. With a 1.2 ohm coil, it will not charge fast enough to spark a high-revving V12. Ferrari has long addressed that by having two separate 6-cylinder ignition systems, complete with dual distributors.
Jaguar went with dual coils with the primary windings wired in parallel. In the main coil, when 12V is applied to its primary winding, energy builds up in the magnetic field, and then when the 12V is suddenly cut off, that energy develops high voltage in the secondary winding and is sent to a spark plug. Meanwhile, in the auxiliary coil, 12V is applied to its primary winding as well, energy builds up in the magnetic field, but when the 12V is cut off the energy cannot go anywhere in the secondary winding because the HT terminal is sealed off. So instead that energy goes back through the primary windings, sending a powerful current back to the primary winding of the main coil. That energy therefore boosts the spark being generated in that main coil.
Iām pretty sure Jaguar didnāt invent that. Waaaay back in the day I once built a model of a Cobra that could be assembled as either a street model or a competition model. One of the differences was that the street model had a single tiny little ignition coil while the competition model had two coils mounted one on top of the other. I didnāt understand that until I learned about the Lucas CEI system in the XJ-S.
Thank you for the clarification Kirby. I may have missed understood from The Book that performance would or could suffer around the 4500 RPM range if the the secondary coil was disconnected.
I guess my question would be could you limp the car home OK at lower RPMs with just the primary if the secondary was disconnected or crapped out on you.
Sure, itāll run fine as long as you donāt rev it up.
Just installed my new coil Keeps wanting stall at idle.
So Iām thinking best to replace both with new coilā¦not go to oneā¦I might want to rev it up!
Iām thinking of going back to two , I did my first shakedown run with the new one and as soon as it warmed up she wanted to stall at the lights on low idle
Iām thinking I discovered my new epoxy filled single coil problem is. I was able to limp the ole girl home (the car too LOL) if I kept the revs up. As I got back into the garage I could hear this arcing and sparking.
Turns out the HT lead connection on the new coil is about min 3/8ā deeper than the original so the lead from the distributor was not fully seated or connecting. Not sure what the quick fix for this would be except find a HT lead with a longer connection point.
OK scratch my earlier posts, I rechecked all my connections and the HT leads. It was still doing the same arcing and burning smells in around the new coil somehow somewhere. I called my friendly Jaguar dealership to see if there was a warranty on this part that has been in the car for less than 20 minutes before starting to stall at low idle RPMs. My parts lady said they would like to test it(which makes sense) or I could check with my local old Jaguar mechanic and try flogging it to him.
I put the old 30 something year old original coils back in and the car runs awesome.
If thereās ever an argument for if it aināt broken leave it the hell alone. Car runs great. Now that I look at the box the part came in it looks like itās been around the world twice and put back wet as a faulty part. It also said Made in France on it ? Seems like a strange place for a Jaguar part to come from?