Logging my ignition problems for posterity

Given the many ignition problems I have had, I thought I would chronicle them for posterity sake so that others might have the benefit of my experience. As many of you know, I have had a multi-year odyssey with my v12 in which left me stranded on the highway no fewer than six times. So, here goes:

  1. Hot condition shut down – the dreaded Opus failure mode. Used compressed air to cool off until ReOpus installed. Still had many problems, but it turns out it was not the ReOpus.

  2. Engine cranked but would not catch – coil failed; replacement given by a usual was wrong ohm and stuttered and backfired. Replaced with proper coil and it worked properly.

  3. Engine would crank and catch, but could not idle – ballast resistor failed.

  4. Engine died with corresponding drop in tach to 0. Also at the same time, there was a second hesitation before the engine would start cranking after turnin gthe key to “start.” – Short in ignition harness (white blue wire to ballast resistor and to tach). Note, this was not a true short but failing insulation on the wiring and once the wire was isolated the engine dying and delayed starting symptom disappeared.

Feel free to add any other conditions you have encountered and the observed solution.

Lundabo,

Thanks, but what year and model Jaguar do you have?

Regards,

Paul M. Novak

1990 Series III V12 Vanden Plas

1990 XJ-S Classic Collection convertible

1987 XJ6 Vanden Plas

1984 XJ6 Vanden Plas

1969 E-Type FHC

1957 MK VIII Saloon

Ramona, CA USA

73 V12 OTS – I used to have that in my sig and forget it no longer shows. Bill

Hi Lundabo,

I am curious as to whether some of these problems introduced the others.

I myself have observed that certain issues (like a misfire from oil contamination in a cylinder) can cause ignition failure (the misfire stresses the coil, which stresses the ignition driver). You find yourself chasing your tail replacing one part to find another failing a short time later.

In your situation I wonder …

If the Opus started to fail … this might have stressed the coil - failure with current through the coil would overheat the coil.

It may also have stressed the ballast resistor. Or the failed coil could have.

In fact, may be the intermittent short from the insulation failure might have taken out (or confused) the Opus.

I guess what I am saying is that it wouldn’t surprise me if all these things are linked in a sinister chain reaction.

Regards
Mark

That may be true. my suspicion is that the bad wiring was/is the source of my problems and did cause damage to the other parts. But who know?

FYI I use my opus module to trigger a HEI module that is connected to a high current coil and starting is much improved. The Opus module stays cool since it only provides a signal to the HEI module.
I also use a relay connected directly to the battery to provide power to the ignition system, the power from the ignition switch only has to activate the relay.
Chandler
78 XJ12L, 83 XJS, MS-1

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I use my opus module to trigger a HEI module that is connected to
a high current coil…

How do you do that?

– Kirbert