My 1991 XJ-S 5.3 V12 has suffered a serious breakdown. The Marelli distributor has seized and stripped the jack shaft. It looks like this is an engine out repair to replace this internal part. Neither the shaft nor the distributor are available anymore.
Anyone run into this? Any ideas or thoughts would be greatly appreciated. This level of work is beyond me, so I will have to have a shop do it, which will likely cost more than the car is worth. It is in great shape other than this problem. Thanks for any help.

 

Have you looked into going distributor-less (Megasquirt)? Thats what I would do.

 

Megasquirt Support Forum (MSEXTRA) ? Jaguar V12 (View topic)

 

 

Do the high tension leads come directly out of the coil packs? How many coils are used? Getting rid of that distributor gives a much cleaner view. Interesting how the throttle control spindle was moved to the front.

 

If the jackshaft gears have stripped at the diff drive, going distributorless is an realistic option. But do check the cog at the shaft drive end where the timing chain turns the jackshaft is not also damaged. If this is also broken then the shaft has to be changed regardless. How easy it is to set up the timing advance curve (and fuelling if you go with that too) properly with a new system I have no idea, but it is worth checking that it is doable/buyable before you opt for it.
If you decide to replace the originals, I am sure a second hand dizzy can easily be found, ditto jackshaft quite cheaply. Getting them in is a big job though, as you say. It would be easiest of all to buy a complete engine from a breaker and drop it in.
Greg

 

Thanks for the input. The engine in the pic sure looks tidy. I will investigate the condition of the jackshaft and look into Megasquirt if it is an option. If I go the engine swap route, is it a problem to go with another HE V12, but an older version with Lucas ignition? 1987ish. Thanks.

 

I'm not sure about the compatibility between years. I do not think Jaguar changed much though.

Going distributorless is going to take some research. However, it will run much better, probably last longer, be easier to work on (with more space) and you will never have to worry about a Marelli fire again.

 

A Lucas ignition engine is identical mechanically. You would have two choices then:

1. find a Marelli dizzy and install it in place of the Lucas dizzy (easy swap) along with the two sensors (front pulley one and the flywheel one). In which case your existing loom amps coils etc just plug in) or
2. hook up the Lucas ignition system on the replacement engine to your car's loom. Assuming the engine came with all its bits (amp, amp loom, Lucas dizzy etc) this would be quite doable too, possibly a bit more work than option 1.

Greg

 

That front sensor mount is part of the timing cover so something would need to be fabricated if going on pre marelli motor. The rear sensor mount is just incorporated into lower flywheel cover plate so it would not be a problem.
Megasquirt or similar would also need something in the way of sensors I assume so finding a marelli motor would certainly be the easiest way out.

 

If you go with Lucas ignition you will need to change the ECU tach input from the Marelli ignition unit to the Lucas Amplifier.

Going distributorless is the best way to go and my not be much more effort than converting to Lucas.

Either way it will require work.

Easiest option would be to find a post 1989 engine or cheap car.