I know that the marelli ignition systems on xjs are known to have problems but is the earlier systems any better or reliable? thanks

 

I don't know if the earlier Lucas systems are any better or worse, just different problems. Perhaps the Lucas is an easier system to work on/diagnose because it has less to go wrong with it, and could probably be switched over to an aftermarket system a little easier.

 

The Marelli system is reliable IF the system is well maintained. Problem is, most owners don't know how serious the results of neglect can be....and the failures occurs with little warning. Regular inspections of the cap and rotor, correctly gapped plugs in good condition, and plug wires in good condition will usually prevent the infamous meltdown failure. Less common but still problematic is spontaneous failure of the coils and control modules.

IMHO the old Lucas system is less worrisome. There are three problem areas: mechanical advance mechanism seizes, the vacumm advance cannister goes bad from age and heat, and the ignition module fails.

The mechanical advance can be unseized....although a distributor strip-down is sometimes needed to do so. A few drops of oil every couple years will prevent future problems. The vacuum advance cannister can be replaced and you're good to go for another 15-20 years. The ignition module, a known weakness, is easy to replace and inexpensive. You could replace it every 8-10 years and probably never have a failure.

Mainly, though, the advantage of the Lucas system is that if a problem DOES occur the consequences are not dire.

I presume tha Jaguar went to the Marelli system becuase they couldn't accurately control the timing with the old Lucas system. That's fine and well, if it's true, but IMHO the Lucas system is the better system viewed from the perspective of a hobbyist and DIY mechanic trying to minimize repair expense and worry.

Just my 2-cents worth

Cheers
DD

 

The Marelli system has full electronic ignition control using a VR sensor and 3 tooth reluctor wheel on the crankshaft. Ignition timing is controlled by the ECU so the only way to change timing is reprogramming the ECU. There is no Distributor control for ignition timing at all apart from aligning the notch in the dissy.

The distributor uses a dual wiper rotor with one wiper for each bank.

I have not had any experience with the V12 Lucas system so I can not compare.

I think upgrading to a distributorless system would be easier from the Marelli as the VR sensor is already there as are the reluctor wheel mounts although a 36 tooth wheel would be needed for most aftermarket ECU's