XJ6C Sudden death syndrome

[klass6]

My annual rite of spring is the shakedown cruise of my beautiful red Coupe. Every year brings a new thrill and challenge. This year, having defeated the curse of the heat related flooding Jensens, a fresh disaster occurred. After about 30 minutes of trouble free driving, the engine suddenly died. No sputters, no coughs, RPMs just dropped suddenly from 3000RPM to zero, power steering gone, servo assist brakes gone. After pulling over to safety, the car would not restart. Battery and starter motor working fine, no sign of flooding ( gas odor free). But no sign of life despite cranking. After about 30 minutes rest, and fiddling with the central distributor wire, the car magically started right up and delivered me safely home. Several times since, I have started up ( no trouble) and just let the car idle with the result ( occasionally) of the same sudden death syndrome. Amazingly, despite not being able to restart (without any intervention), the simple act of attempting to check for spark ( i.e. removing a plug and getting my wife to run the ignition) has resulted in the car starting right up! It seems that something is up in the distributor, but can some genius pin point the problem for me from this strange set of events?

 

[Deleted member 8987]

Ah, yes.
Seen that LOTS of times in other marques.

Pulling the plug wire increases the spark voltage to overcome the big gap.

Coil is my guess.
Heating up and going open-circuit, or intenally to ground, you pull a plug wire it has to generate more power and begins to live again.

Look at your wires, cap and rotor carefully.
I would stick a coil in it, and a new rotor for sure, checking for carbon tracks on the cap and looking at the ends of all the plug wires carefully.

Also, start it up with the bonnet up at night, get out, turn the lights off outside (or in the garage) and look for sparks.

Could be your electronic ignition, but I've seen that on points-controlled units, too. A test for heat issues in ignition control boxes is spray air cans.
Hold it upside down and spray lightly the component in question, then immediatley try to restart it.

Dave

 

[klass6]

Thanks for the insights.
I'll work through these and see what happens.

 

[jessebogan]

Do you still have the "opus" ignition? Might be time for an upgrade. A series 3 distributor and lucas amd should be available in most big wrecking yards. (Jag offered a similar update "back in the day". The series 3 stuff works well, and the amp uses a GM chip inside that is really easy to source at local parts stores. (Just don't tell them what you want it for.....)

 

[LarryK]

I've seen the sudden death syndrome on quite a few XJ6s. On my 73 it took a while to find it. Seems with the heat of the engine the terminals would come loose. I replaced all terminals with circular terminals and brass nuts. When it happened on my 79 XJ6 on the way to work, found it immediately and changed all when I got home. Seen this occasionally in older XJ6s. If you look at your terminals at the coil the wire will look dark instead of copper or steel color.