MSD Ignition on V-12 Jaguar E-Type


I was recently asked a question about the Jaguar Ignition system in the Jaguar V-12 E-type Engine Video that we produced. The original ignition system was an Opus system made by Lucas. When I first saw the car it had the Opus unit replaced already with an older Crane 700 Ignition system. The problem was the car had a misfire that started at 3,500 RPM and continued preventing the engine from reaching higher RPM’s. I checked all the usual problem areas and felt it was an ignition problem. The Crane system seemed to be OK but when I checked the cycle rate the unit could manage it showed up the ignition problem. (From this point on I am assuming the reader is familiar with how an engine and a basic ignition system work).

On the V-12 engine the ignition coil fires 6 times each revolution. At 3,500 the firing cycle is 21,000 per minute. This is approximately the listed limit with the Crane unit. So the unit was working fine but it just could not manage the high firing or cycle rate even though it was a kit sold specifically for the V-12 Jaguar. The system needed an upgrade, but I wanted a simple straightforward fix still using the distributor and a single coil. Rather than trying to build a multi-coil crank triggered system that also would require an advance and retard system. Plus I had to work to within the customer’s budget.

I decided on a MSD Capacitive Discharge unit. The type being the “6” Series which could manage the firing/cycle rate. If you read the description the unit basically gives a double spark at lower RPM then drops to single spark once the RPM’s reach a higher point. These units will work with a distributor running various sensors/triggers or even points. They work also with ballasted or non-ballasted coils. The original Opus used a ballasted coil. The Crane unit had been fitted using the same ignition coil and ballast as the original.

The main problem was having a trigger or sensor for the distributor. There was not a lot of choice for a 12 cylinder. The original Opus system used a magnetic sensor with the 12 magnets embedded in the timing rotor. This was not really suitable for use as the magnets are really quite weak for newer sensors or triggers. So I decided to use the timing rotor that came with the Crane system. This has an optical trigger which has no magnets just slots. Unfortunately the optical sensor that comes with the Crane V-12 system sends a sine wave signal to the amplifier (the Crane Ignition Box) which is not suitable for the MSD Box or Amplifier. It requires a square wave signal to respond which requires the optical sensor to be changed. The square wave sensor has three wires and the sine wave sensor has two wires I believe. (It was awhile ago since I did this repair).

This square wave sensor can be obtained from Summit Racing on its own. Though the Timing Rotor is in a Ignition kit from Crane for the V-12 Jaguar (sold by Moss Motors). You may need to buy the kit to get the timing rotor but you also get the mounting pieces for the sensor which will make life a lot easier. Having said that, it is a bit of fiddling to get the setup mounted correctly. The advance and retard are taken care of because you are still using the distributor. To set the static timing you need access though the timing rotor to the allen screws in the distributor base. Also something to think about if you are thinking of making a custom Timing Rotor.

Below is the wiring Diagram for the MSD-6 type Ignition. The are several different variations of series 6 boxes with extra functions. I went for the basic unit. There is an adapter required to enable the Tech to work from the output on the box. If you are testing the unit after fitting everything remember to fit the distributor cap when you try it. The optical sensor works from light so it needs to be in the dark to work.

I set the system up with a Lucas Sport coil without using the original ballast resistors. Later I changed to a MSD blaster coil as it was a matched part.

msd wiring