[xk] Ignition Coil Failure

I very much agree that coils tend to get a bit of bad press, often unjustifiably. I wasted a lot of time changing plugs, coils, rotor arms, points and distributor caps chasing down a hot misfire on an XK engine. Each time I thought I’d fixed the problem because everything had cooled down enough by the time I’d changed the component under suspicion.

It turned out to be the plug leads which had come as a set from one of our well known suppliers. I was reluctant to suspect them because they were only four years old. But in the end I bought the best quality HT cable I could find and made up my own set. Problem solved.

It gets damn hot under the bonnet and the insulation on the cables was breaking down.

Eric
Shropshire, UK

Rob, I asked the distributor doctor here in the UK what col to use following his refurbishment of my 120 distributor. I have chosen to use points and condenser rather than Petronix module. He recommended the ‘flame thrower’ from petronix as its ‘bullet proof’ it has a 3 ohm primary. So far its been perfect in some pretty hot conditions. I suggest you try one and see if you can eliminate the coil as an issue. I have had many issues with new manufactured Lucas units and other modern equivalents.
Just my opinion.
Best regards
PAD

some like Pertronix or similar…123, Mallory…but I see a lot of posts with troubles that can not be determined with the various electronic distributor bits. XKs ran for years, won races, 7 days and nites at 100mph…with the Lucas distributors, Points can be observed, adjusted, changed. So…its std distributor, for me. As to this thread, it seems that a coil swap being so easily done is step 1. U;d have to do some research to prove to myself what non Lucas coil may meet the XK120 needs. Use very low, or no supression spark plug wires…most newer wires have VERY VERY hi suppression…a 1.5v battery continuity test lite will not lite. You want 1 ohm or less for the full wire length. Easy test on your wires…a continuity test lite check…it will…or it wont…lite.
Nick

As always, each to their own, but your example is a bit of a furphy.

Points require periodic perfecting, ALWAYS, and in those endurance races, were often checked every time the car was looked at.

I serviced thousands of p&c, and rember how often they were the cause of poor running.

Again use what you want, but the SINGLE best mod I made to my Jag was the EDIS, and soon will do the same to my Rover.

And, unlike p&c, it’s virtually dead reliable.

not much to add Paul…but since you said.".furphy," there are more than one furphurious “points” in your comments: to wit:
yes…True statement : points require periodic perfecting.
To quote myself…“Points can be observed, adjusted, changed.” and I will add it is straight forward and easy.
Point 2: (no pun): of course when servicing cars back in the day the points needed service…duh…that is all they had…so of course for folks who brought cars to a shop, points needed the "periodic perfecting: "
and…as said…not so many posts here or other car forums on points…because issues with points are so easily diagnosed, and easily “perfected”, while the electronic versions seem to drive many on wild goose chases to "points " unknown…
I have made my “point”…and you yours…To each his own…
Nick

Absolutely…and, in vast numbers, now, electronic systems need virtually NO servicing.

Ever.

Thank the powers-that-be that both mechanical ignitions and carburettors have been relegated to the dust bin of automotive history!

How do you adjust points…give me a run down???
Like what tools…what gap…I have nooo Idea

no interest in a furphy match…BUT…electronic…no service …ever…
HA !! as with old points…now thousands of disabled cars electronic ignitions, computers, control modules, spark plug coils and more…with no possibility of owner/operator roadside repair…thousands…just look at any car forum…includin this one with Pertonix, 123 etc perplexing problems…then move on to the modern forums.
Nick

Just to highlight a modifier you left out.

I stand by the statement, and I lived through both: electronic ignition systems are FAR better and more reliable than the best points and condensors.

I aree with the “mire” part.
Nick

This is an interesting debate and one which we had on the E Type list a few years back.

I don’t think anyone can dispute that modern electronic ignition in modern cars is vastly superior to a points based system. However, the kind of aftermarket electronics (Pertronix, 123 etc.) is not comparing like with like. The ignition systems in modern cars are part of an integrated whole, complete with all the sensors and processors necessary to make it work. These systems are developed by manufacturers with huge resources and tested to the absolute limit under every stressful condition that they can dream up so it’s not surprising that they work so well.

I put it to you that the Pertronixes of this world do not come from manufacturers anything nearly so well resourced and I doubt they can apply the same test regimes as the car makers do. When they are working it is indisputable that they are better than a CB system but they do fail, which if the complaints on the forums are to be believed is far more often than you’d like, and when they do you are royally stuffed.

The point has been well made - your car, your choice. But for me, the CB system was contemporary with the rest of the car. The reason I own and run classic cars is to relive the experience of that era of motoring, warts and all. I’m not bothered about improving on it but neither am I suggesting that I want to break down by the side of the road. But if I do I want to be able to fix it.

Just my tuppence worth.

Eric
Church Stretton,UK

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That’s why I leapfrogged right past the Pertronix, replaced my Mallory Unilite, and headed for an EDIS: those components are indeed well-made and robustly-researched, and darn near bulletproof.

To reiterate: Im perfectly happy if folks want to run CB ignitions, to have fealty to the era in which the car was made.

I just cannot let it stand that they are superior to modern ignition systems: they are not.

The vast improvement in performance that the EDIS made to the Jag was astonishing, reversible, and worth the small cost of conversion, if for no other reason not having to stuff my tubby body down twixt the bonnet and tire, to service the stupid points!!

Can’t wait to see and report on, the Rover’s subsequent conversion to EDIS.

Thanks! Fixed my typo.

ohhh…typo…I thot it was correct as it was…!! :slight_smile:

Yup…that’s what I’m talkin about ! As said, Points are easily observed, adjusted “re-dressed as Dad always did”, or changed…roadside with not much more than a small screwdriver. Don’t even need a feeler…a matchbook cover will do it. I have little interest in what others like, not trying to change any minds…just presenting what I like and why, others can select the type, but either way…some time, some place…the system will need attention. “virtually reliable” means NEARLY and Almost… Now…if the virtually trouble free starter on my other car, would just start the car…which it is not…Nick

Turn the crank carefully until the brown points shoe or rubbing block is at the peak of one of the cam lobes, i.e. points fully open.


Loosen the two screws holding the points base plate just half a turn.
Moving the points base plate gently with a screwdriver, set the points gap with feeler gauges to Service Manual spec, early cars with smaller cams .010-012", most others .014-.016" and tighten the screws.
Check it again. The feelers should just barely drag on the points.
Turn the crank a bit to ensure the points are closing and opening again.
Reset the ignition timing.

Other tips:
The points base should have locking washers of some type, coil springs or star washers.
Notice the little wire that comes from the coil and connects to the terminal on the side of the distributor body. Inside is a wire connection that goes to a black terminal block and should connect ONLY to the springy side of the points and the capacitor. If it touches ground the car will not start.

Eric,Nick,
Maybe I’m like the old Lil Abner character that walked around under a black cloud but over the past 35 or so years I’ve had a failure on a Lumention and recently on a Mallory electronic ignition system and my son had a Petronics fail a few years ago and all were using the proper coil, wires etc. I probably should have bought one of Ray’s systems but didn’t so now I’m back to the old P&C system, somewhat a PITA that in 60+ years of driving they never have left me sitting on the side of the road. If we were still putting the miles on the E that we did years ago I’d put a new module in the Unilite as the older I get the points, for some reason, are harder to get at, but with the few miles we drive now days I’ll stay with what I grew up with.
Bob

You are lucky: I lost count of the times a bad condensor, or set of points failed on me, and/or many of my customers.

I was not sure if Mitch was serious…but ok…as Rob said…and often when re tighten the tiny screws I leave the feeler in place but still…the point gap adjust plate may move a little when you tighten the screw…so have to re=set.while .tryin on the screw titen to keep it from moving as you tighten. When tite recheck the gap with the feeler. I like to do this with the engine already set at #6 (front) cyl at the degrees I want Before Top Dead Center., on compression, .so that I can check timing easily. Timing means that the points are just opening at the degrees BTDC of # 6 on compression, that you want…say 5, or 7, or 10. (the rotor will be pointin toward the #6 spark plu wire on the distrib cap…so note where that is before takin the cap off. There may or may not be timing marks on the damper by the fan…and there is probably an arrow mark on the flywheel that can be seen thru the small opening near and above the oil dipstick. That arrow “should” be when # 6 is at TDC…need to coincide with distr rotor at the # 6 fire position…usually toward front of car…about 3 o clock as you look in / down from rt side fender.
There are many on line descriptions,including a search on this forum where you will find a lot, and you tube videos on setting point gap and timing. If an out of the car points sample distributor (any will do) can be on you bench then it is excellent easy practice when you can actually see close up. By the way…the Jaguar distributor rotors turn counter=clock in operation…With the car in 4th it can be pushed forward just a little at a time…neutral to roll back…then 4th and forward again. Helps to have a helper pusher…while you watch the rotor/points. But can be done, car in neutral, wrench on the front crank bolt head…turn clockwise from your point of view as you look inward from under radiator…but not this is same as counter clock from point of view of a driver in the seat looking forward. Much easier to rotate engine in either case of spark plugs are out. Since doing a points/timing tune…may as well replace spark plugs,proper gaps there too… anyway. Call this most of a minor tune up. (but w/o the somewhat trickier carbs adjust) Some will say this is useless without properly set carbs…which is “virtually” true. (nearly) .(note I often say…“should be” and “may be” because prior owners may have changed things from original…how do I know…my flywheel is 180 out…my old distrib was also set up differently.).
Nick

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Bob and Nick
I want to thank you…

my 2+2 i have driven all over…like from Phoenix to Colorado and back…it occurred to me I really did not know how to set the points…now I do it is pretty straight forward. I have set the timing using the 34 all in. It does run well…I did just convert it to MOD and replace the crank as it was scared…it seems the center carrier shell is prone to this…I did cut the lower chain and put a connecting link in…was not reco’d…we will see…

Oh, I have collected 8 xj6 engines so I do not care if the 2+2 engine disinigrates why I could justify the link…to be honest the xj6 in my ots is alive while the E engine is…OK…

I talk to much…

Again thanks

mitch