All my experience with Jaguars has only been on cars with Lucas ignition systems.
I am considering a looking at a 90/91 convertible (VIN 1673xx) with the Marelli system.

Other than the normal potential issues: belts, hoses, plugs, wires, T-stats, steering rack, radiator, oil leaks, fuel hoses, steering bushings, brakes, wipers, AC, fans, electrical shorts, overheating-dropped heads, what should I be concerned about with the Marelli system and what if any are the tell tell signs of past or future problems. What if any special maintenance is necessary to enhance the reliability? If maintained how reliable is the system?

Any other input is welcome.

Thx/
BH

 

Brad,

Others who have suffered worse may have a different view, but IMLE, it's all about the Distributor, Cap & Rotor Arm, that are the root cause of the infamous failed bank problems.

Paul

 

I would say they are less of a headache as the ignition system is digital so there is nothing in the distributor other than the 2 level rotor. The advance curve map is way better but it is a premium fuel car. When we had the "88 H&E I did look at a '91 which of course was Marelli. The performance was like night and day between the two even though they had the same 5.3l displacement along with the turbo 400 slush box.
On the '88 I had to pull the distributor to fix the advance weights and replace the vacuum capsule. The car ran great and responded well to every tuning adjustment made but still no match for the Marelli car.

 

Because of awareness the Marelli cars should be less of a problem now than they were decades ago.

Make sure your plugs are gapped at .025" and that the plug wires are 100%.

Annually inspect the rotor for burning.

Buy an extra cap and rotor while you still can. They'll be aftermarket but you have no choice. The true Marelli replacements have been out of production for years. The aftermarket stuff seems to work OK but doesn't last a long.....which makes regular inspections that much more important.

If you're driving and feel a loss of power turn off the engine immediately and don't drive again until the cause has been determined. It might be a Marelli burn-out. Continued driving can actually lead to engine fires.

Cheers
DD

 

So what fails? The rotor? The cap? One side shuts down and the other keeps dumping raw fuel into the combustion chamber without spark.

Rotor burning?

On my Lucas cars I switched all plug wires from OEM 7mm to 8mm with a dramatic reduction in free floating electricity in the engine valley. I assume upgrading OEM level plug wires on Marelli cars is highly recommended.

 

Take a look here:
https://www.jag-lovers.org/xj-s/book/Marelli_pix.html
I don't think that it has to be as bad as some have experienced. Look in Palms book for a solution. I didn't trim the nub on the distributor down as he mentions but did fill the core with silicone. He also mentions in "The Book" using a Lucas distributor with a special automatic coil selector to split between the two coils as another option. Of course you'll have to gut out the distributor and pin it solid which isn't very difficult.
But all in all, it is a much better ignition system than the old Lucas one.

 

The rotor is what usually fails





The cap...less often



Cheers
DD

 

Doug, hit the most important point, the cause of Marelli issues is improperly gapped plugs. This wasn't unique to Marelli, as automakers moved to digital systems and performance cars used higher voltages. Given the high energy involved, any electrical system with too much resistance is going to fry something, and too large a spark plug gap will do the same. I'm not sure even Jaguar engineers were aware of how critical this was to component longevity, because it isn't mention in the Marelli Supplement when they introduced the system.

Additionally, there is a Marelli "fix" in the Palm book which helps prevent arcing issues. I think that if you properly gap the plugs and do the Palm fix, it is quite trouble free.