Greetings, just joined today, bit desperate, on family visit in Germany with my '89 V12 XJS (automatic) which, after a brief stop in Munich, decided to run on half an engine only; left bank running fine, right not igniting. RPM meter stayed on zero. Managed to trundle (below 60mph) to our final destination on my new V6... Hope I haven't caused damage to the engine though it seemed to manage without too much effort (3rd kicking in quickly).
QUESTION is obviously, what could be the likely cause of this failure? Where should we start looking?

Any help most welcome.

Thanks,

Frank

 

Frank
Do you have a Marelli ignition car (two HT leads going into the dizzy cap from the coils)? Or a Lucas ignition car (one huge twelve post dizzy cap)?

If the former, Marelli, this might be a dizzy cap failure, quite common, under which no spark gets to one of the banks. This can also be serious as it can cause an exhaust fire as unburnt fuel is passing through the engine non-firing side to the catalytic converters (if you have these).

Post back the details and the Marelli experts (or Lucas experts) will give you some ideas about what to do.

Greg

 

Do you have the Marelli ignition system? If so you almost certainly are experiencing the infamous distributor rotor burn-thru.

This can pose a real problem, up to and including fire. Don't drive the car.

If you have Lucas ignition the most likely cause is an injector harness fault.....not that an injector harness fault is impossible on a Marelli-equipped car, mind you.

If unsure which system you have.....

The Marelli system is easily identifiable by the two square-ish control modules on the radiator upper mounting panel. Or, what are the last six digits of your VIN? Marelli ignition was introduced at about 156xxx (exact number varies from source to source). If your is 157xxx or higher you surely have Marelli. If 155xxx or lower, you shouldn't.

I suggest that we identify what you have before discussing a plan of action.

Cheers
DD

 

Hi Greg, hi Doug,

Don't have the car or the papers at hand at this moment, but googled the images for both systems and I'm pretty sure it is a Marelli on my car. As Greg mentions it seems to be a rather common issue so I hope (hope) the local German repair shop may be able to handle this swiftly. Parts procurement may be a problem though, but perhaps a servicing of the system may do the trick.
Thanks for your help and encouragement so far. Any tips welcome.

F

 

If the rotor has indeed burned thru then replacing it will get you home....at which point you'll probably want new spark plugs and wires installed. High resistance from either will cause future problems.

This XJS tome has lots of Marelli info:

Experience in a Book

It's also possible that one of ignition modules or coild has failed. The repair shop in Germany should be able to determine this if they're somewhat familiar with old Jags.

Cheers
DD

 

Hi Dough,

Vin 160***, so that's ccnfirmed.
Just been serviced (15k) and spark plugs have been replaced less than 1k miles back.
It might be the coil or ignition module? I had one single occurrence of this problem 6 weeks back, upon which I made the appointment for repair with my UK garage. And promptly the next morning the problem was gone...

Thanks again,

Frank

 

Yeah, a burned-up rotor isn't likely to give a here today, gone tomorrow symptom. Coil, module, loose wiring connector......

The shop should inspect the rotor just to be sure. Coils are easy enough to test. That leaves modules and wiring. There's almost certainly a test/spec for checking the modules (though I don't know what it is, personally) and the wiring is mostly visual inspection.

You're actually at an advantage now that the problem has gone from intermittant to 'hard failure'. Easier to diagnose that way.

Cheers
DD

 

Modules and coils are easy to test.

Modules - swap the large input connectors between the modules and then swap the connectors on the coils. This will run each bank the the other module. If the problem stays on the same bank the module is OK. Swap the module input connector back but leave the coil connectors swapped

Coils - With the coil connectors still swapped swap the HT leads on the Dissy cap. This will run each bank on the other coil. If the problem stays on the same bank then the problem is in the Dissy.

 

UPDATE:

Thanks everyone for your help.

It was indeed the ignition control module, DAC 11520.
Procurement over the holidays was difficult. Got ordered on Thu Jan 2, installed Sat Jan 4. Including shipping it cost me app. 300 Euro.

NOTE: I know this car very well (owned it since 2004, driven 60k miles). It seems fuel consumption has dropped remarkably, from 20.0-21.0mpg range to 23.0-24.0mpg range over the last 300 miles on the German autobahn. Probably should have checked/changed it years ago... How about the right side & is there a good way to test them?

Cheers all

 

This came from the Jag Lovers part interchange...

The Marelli ignition amplifier for the latest V12 is very expensive - used ones sell for more than %50-60 on ebay. Standard part# LX1016 is a common cross-list product, albeit also very expensive ($200+ new). The CAMBIARE part# VE520225 costs less than $40 new and is direct replacement. Used in Fiat, Alfa, Lancia and other Italian cars.

Ignition Module Jaguar DAC 11520