123Ignition Hot Start Trouble

Has anyone had difficulty starting their 123ignition distributor outfitted XK when it is very hot ? I installed mine about a week ago and it has been phenomenal ! Amazing difference. The car has never started so easily and run so smoothly.
However, today I made a 104 mile drive, in 75 mph interstate traffic, from Atlanta up to the mountains. It was 95 degrees in Atlanta ! The engine bay was hot as hades. Near home, I stopped for lunch (about 45 minutes) and when I tried to start the120, it wouldn’t fire. The starter spun the engine and not so much as a cough start.
I continued to try, and I could tell that the carbs were getting fuel in the clear glass fuel filter at the carbs and I could smell gas. After about 25 minutes with the hood open to cool, I tried and it started after less than 1/2 a revolution, hummed smoothly, and reved solidly.
I am wondering if the 123ignition has an automatic cut-off, as a safety when it gets exceedingly hot, and wondered if anyone else has experienced this.
Thanks for your help, and stay well, Knight

Ouch! I can’t help as I just installed mine, but certainly interested to hear.

Hi, I drive also with the 123, never have problems with heat. I think your problem is somewhere else. Vapor lock? Ignition coil?

Hello, I have the 123 Ignition on all my 3 Classic Jaguars, never a problem.
Looks more like a coil issue. I have the High performance coils.

Peter Jan

Easy way to tell if it’s an overheating coil: when the problem arises, wrap a sopping wet towel on the coil: if it starts, you have found the likely cause.

The higher energy spark you get with electronic ignition comes with higher current flow and resulting heat in your coil. Did you also change you plug wires to resistor type from the solid copper original wires. Could help to reduce heating of your coil and new ignition module. Expect your new 123 system came with recommendation to change out your old copper plug wires.

Thanks to everyone for their input. The Coil is a new 1.5 ohm FlameThrower which is what 123ignition recommends. It replaced a Lucas Sports coil that was also new and that 123 also says is fine.
One of the attributes of the 123 mentioned in their promotion is an automatic cut-off after 1 second to avoid overheating the coil. So, I wrote to their support and asked if it was possible that the automatic cut-off did so and remained cut off due to heat, perhaps ?? They simple wrote back “no”.

The good news/ bad news is that I may never be able to effectively diagnose it since I doubt the car will be under such extreme conditions again anytime soon . 3 hours at 75mph is 95 degree weather on the interstate was almost as tough on the car as it was on me ! :-)) Drove it this morning for a couple of hours with no issue but, then again, its 65 degrees up in our mountains !
Thanks again and stay well.

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In a 120? I cannot even imagine!


The dumbest thing, on my part Paul, was not putting the top up to keep the sun off of me. So, I’m a little cooked today. Other than that, the car settled down and cruised nicely. I really do like the 123Ignition distributor. It accelerates much more smoothly, idles without a hiccup at 400 rpm, (read that part again :-)), and cold starts, without choke, before a complete revolution. Cheers .

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Sounds like vapor lock and ethanol gas…Isnt teh 123 great!

It is a great distributor ! In the 40 years I’ve had this car, it has never run so smoothly !
I feel sure that the difficulty I had was something to do with the other components, but it wasn’t vapor lock. I have experienced vapor lock a lot when the car sits hot for that magic length of time ( usually 20 minutes ), and know its behavior. This was not like that and I only put non-ethanol gas in it. I have driven the car a few miles since without issue and it runs like a champ.

I also have the 123 Bluetooth version on my 120FHC, but not had those symptoms on hots days when we get them in U.K. !!

But, I thought my Coil is 3 ohms not 1.5 ohms, is not 3 ohms what the instructions say ?

Ive only used 3.0 on all my three jags as well.