Can't really feel the wear on the cap terminals with my fingernail, the rotor feels gritty though, so question for those with experience, does this warrant replacement?

I've no clue when the PO may have replaced it.

The wires from the dizzy to the coil are baked and not too flexible, so those will be replaced, but the plug wires seem pliable and soft. Is a resistance check sufficient or what's the wisdom on this?

Plugs look nice and tan colored, but I'll be replacing them anyway to get a baseline.

 

If it was my car, I would replace the dizzy, the rotor arm and the HT leads. HT leads give up after a bit and "leak" out the spark quite a bit, often this is visible in the dark, they do not have to be brittle to do this. The cap terminals look like they have been physically worn away by the rotor arm, maybe an incorrect arm was fitted before? Check when you get replacements that the arm is close to the dizzy terminals but does not actually scrape them.
Greg

 

I agree with Greg.

That is a sad cap. Something is out of whack coz as he said, the rotor "looks" like it is striking those posts, which is a NO NO.

The gap is what we all call an "air gap". The arcing fom the rotor tip to those posts can leave a groove after a very LONG usage time.

I would check the centre shaft on the distributor and "feel" for ANY sideways slop/movement in it, which would be enough to cause the rotor tip to collide with those cap posts.

That centre carbon brush also looks very sad, and that is usually caused by too high a resistance in the leads.

New cap, rotor, leads, would be a minimum in my fleet.

If that short loom from the distributor to the amp is hard and brittle, that thing has seen some serious heat. That loom is Stainless wire inside, not Copper, and is more "flexible" than Copper wire, and stays that way for eons.

 

Appreciate the feedback, the parts list is getting pretty long

Did not know about the difference in wire material. The fuel injector wiring is pretty decent and pliable/flexible and based on pics others have posted I was expecting that to be replaced. Go figure!

I was thinking of using 10 gauge copper/silicone wire for the dizzy to amp replacement. Mine is the twin coil setup, stick with that or move to the single coil?

 

Advice from Grant and Greg doesn't require back-up from anyone, least of all me, but FWIW....I agree with it



Par for the course with these cars. Virtually everyone who buys one goes thru the long process of catching-up on all the neglected services and repairs. I spent a few thou and many weekends during the first 8-10 months of my XJS ownership get every back up-to-par. After that....smooth sailing with just some relatively minor tinkering from time-to-time.

When/of any particular system needs attention do it once, do it right, do it all....and you're done with it for years. The alá carte method just prolongs the agony.

Cheers
DD

 

I suggest you clean up the coil, do all the low tension coil wiring as you suggest with silicone insulated wire, thick enough to comfortably carry 10 amps is needed, (I would over spec rather than under), do all the other things you listed, but do not change the coil yet.
When all the other things are done, then make sure she starts and runs. After that run her for a bit. If you introduce a new coil while doing these other jobs and then you have starting problems for some reason, it is yet another variable to worry about. In fact I am a bit if a fan of the twin setup and still have it on mine.
Greg

 

There are few things that one can do to an experienced engine that
have a greater effect than not just good, but great spark.


I've seldom messed with old stuff. If any doubt, replace it. but, caveat, with quality stuff. A lot of junk on the market,


In my project before the Jaguar, a hot flat head Ford V8,
I wanted a late "crab" style distributor. sourced a nice rebuild from an enthusiast and business colleague. The cap came elsewhere, not bad. The rotor, garbage. cleaned up and used the original, much better quality.... Original hold down clips nonobtainum.... I found a par of VW units that looked right and were almost perfect. Just a bit of bending... Converted from 6v pos ground to 12v neg. New HT leads and plugs. It fired right up and sounded oh so nice right oput of the headers....


Try the "light show" thing. Crank up the engine and look at it in the darkest place you can find. Northern lights or Tesla coil????


Carl