Marelli Ignition- what’s the latest?

XJ-S
#1

I’m new to this forum as I’m considering buying my first Jag.

The car that I’m considering is a 1991 XJS V12. (US model with cats).

Overall the car is in pretty good shape with some expected issues that I could address over time.

My main hesitancy is the dreaded Marelli ignition. I’ve read at length (on this forum and others) about the failures and potential for catastrophic fires. I’ve read the info in Kirby’s book about potential fixes. Much of the info and advice is from over 10 years ago and I was interested in how successful these fixes have been and advice on moving forward with this car.

Also, it appears that some experts (notably the folks at AJ6 Engineering) remain unconvinced that this a serious or prevalent issue.

Assuming that the car I am considering has 65K miles and still has the original Marelli cap and rotor, please choose one of the following recommendations:

A) inspect cap and rotor: if all looks good, do “silicone squirt” for existing rotor and keep original cap. Continue regular inspections.
B) replace cap and rotor with aftermarket replacements every couple of years; do silicone squirt each time- I assume that it is impossible to buy bonafide Marelli replacements anymore. Any advice as to where to buy quality aftermarket replacements appreciated.
C) replace distributor cap and rotor with Lucas while keeping the rest of the Marelli ignition system intact- I read about this in Kirby’s book. It sounds like a good solution but I’m unsure how complicated it is to do- I’m interested in hearing if people have actually done this and how it went.
D) stay away from Marelli, instead buy a pre-‘89 Jag which has the Lucas ignition system- I’m unclear what you lose in performance (if any) with this older system.

Thanks much

#2

Doesn’t work, because it turns out the MSD Automatic Coil Selector is a POS that burns out in a minute. This fix might work if one assembled their own diode packs to prevent one coil from backfeeding the other, but AFAIK nobody has actually tried it. It’d probably be ugly, as you’d have to assemble several diodes, perhaps inside a hose or something.

The silicone squirt does work – in fact, I’m not sure we’ve heard from anyone who suffered a rotor burn-through after having cut the distributor shaft down a bit and applied the silicone.

Unfortunately, the Marelli can suffer a one-bank failure in other ways, including just having an ignition amp or coil go out. Best advice there is to pull over now when it happens.

If you don’t want to risk the issues with the Marelli, you can go the route that a great many Marelli owners have gone: Replace the entire ignition system with either the earlier Lucas CEI or with an aftermarket system of some sort. The Lucas CEI works fine as long as you keep the centrifugal advance mechanism lubed. And caps and rotors are a lot cheaper. And amp repairs are dirt cheap.

And no, you can’t get genuine Marelli rotors and caps any more. Anything you get new will be aftermarket.

#3

Please take everything you read one this topic with a grain of a salt.
I own a Marelli car. 10+ years.
IMO, it is a superior ignition system to the Lucas. If you stay on top of the schedule maintenance, you’ll have no troubles.
Many here will disagree, of course, and many will have formed their opinions based on forums folklores, not actual driving experience.

In a nutshell, if you lose one bank due to a cap/rotor/coil/amp failure, you will KNOW RIGHT AWAY. Stop right away.

And if you continue to drive it in that condition, even for an extra mile until the next exit, well, to quote Kirby from another post, “you are not cut for a car ownership”

[N.B. I used “car” to make my point stronger, his exact wording included a “Jag”]

Good luck and welcome to JL.

#4

I purposely bought pre-89 mainly to avoid Teves ABS brake system, secondly no air bag so easy steering wheel swap, and thirdly to avoid Marelli. Yes, the Marelli system IS more advanced technology. Both Marelli and Lucas ignitions require modifications as outlined by Kirby in the book, and periodic maintenance. But Marelli failure can be catastrophic with fire, whereas Lucas failure is a lack of advanced timing and maybe a ruined distributor.

That said, the extra maintenance and knowledge of Marelli will probably avoid catastrophe. Its something you just need to check on like changing oil. But you’d still have to deal with Teves abs :wink:

#5

There’s a lower risk of fire with the later cars because they did away with the stupid hoses that go from the fuel rail to the injectors and used o rings like every other car does. The fuel tank and pump assembly was also simplified and more like a modern car.

Marelli doesn’t really cause fire so much, you’d have to really keep driving it to do that, and the engine runs poorly on only 6 cylinders, you’ll know when something is wrong.

I carry a spare rotor arm just in case. My car has had one rotor burn out in its life, causing a misfire, but it caused no lasting damage. It was more of a misfire under load than a total loss of a bank from what I gather.

The computer side of the Marelli system is pretty good. It does away with a lot of the faults and inacuracies of the lucas advance, but the distributor itself is rather poor.

I’d be nice if we could find a cheap way of pulling the distributor out entirely. No more rotor arms! Maybe if a standalone 6 cylinder system exists that we could run two HT leads off from in a wasted spark system, that would work without being too complex. It seems most aftermarket stuff only goes up to V8s.

#6

Thanks for everyone’s reply on this subject.

Sbobev, what is your “scheduled maintenance” when it comes to the ignition system? Does this mean that the cap and rotor are inspected yearly? Do you still have the original cap and rotor? Did you do the silicone squirt?

#7

My car is not driven much. I replace spark plugs every 5000 miles (which for me is 2-3 years). When I do that, I check the HT leads and make sure they are routed away from metal.

Dizzy cap was original to the car when I got her. I am still using the replacement cap and rotor I put in 2010. The original ones are in the trunk.
Coils and amps were replaced in 2011.

I have not done the shaft shortening and the silicone squirt. The way I see it, if the energy from the coil has somewhere to go, it won’t jump through the rotor.

Look up posts from 540itouring. He drove home his car when one of his coils failed on the road. Just disconnected the injector clips (all 6) on the offending bank.

#8

Yes, arguably the bigger concern. Marelli might burn up your car, but Teves III ABS can kill you.

Still, not terribly difficult to ditch the Teves III, too. So if one has his heart set on a later car, it is possible to put it into a state where you can hand the keys to your teenage daughter and not worry about it. Too much.

#9

No shortage of standalone 6-cyl systems. Unfortunately, I think most of them are already wasted spark! So you need two of them. I’ve been suggesting for years that someone rip two identical distributorless ignition systems out of 6-cylinder cars and install them. I think it’d work fine.

#10

I have had two rotor/cap failures since cutting off the top of the distributor shaft and stuffing silicone in the rotor. The stories are posted somewhere in the old forum with photos. It is easy to tell when the rotor burns and shorts. the car will have great difficult moving. Turn it off as Kirby says…do not try to go past the next seam in the road. Pull over and open the Bonnet. If you look below the headers you will see the beautiful red glow deep in the bowels. It is quite impressive at night. Let everything cool down for an hour or so and then open the boot and take out your extra cap and rotor. Install same and be on your way. This is a car that is only used on sunny days for nice drives. It has been on long trips but both failures were after runs on the Interstate of less than 30 miles. One trip ran great. I pulled into the tax office and gave some blood. Returned to the car and drove 2 blocks in downtown traffic and lost power. I have no problem owning the Marelli. Just be prepaired. As said above, it is the rubber hoses that will burn up your car. I suggest that the cap and rotor be removed every once in a while and wiped clean with alcohol and acetone. Take some fine sandpaper and smooth the end of the rotor and the cap contacts. Clean the cap again and re-install. Quality caps and rotors are impossible to find. Read Kirby’s section in the book again about the spring. I have purchased 6 caps and 8 rotors over the past 15 years. It does not seem to matter much which brand you buy as when I opened the boxes I discovered all were the same except for one. Advance Auto listed 5 different caps. I chose one and it was junk at a high price. I returned it and got a cheaper one. It proved to be very good. Same for NAPA and Rock Auto. You will not know until you look at it. Best luck with Beck Arnsley but not always.