Ignition coil heating up

[jddevel]

Following a previous ignition problem with backfiring through both of the carbs it was noticed that the ign. Coil was getting very hot. Coil, points, condenser, plugs all changed to no avail. Engine not running hot. Carbs cool. Heat shield in place along with cover on supply pipe between carbs. Rolling road test showed marginal inbalance between carbs-rectified. Distributor oiled and functioning. New dist. Cap red rotor arm and recent leads. Now pulling hair out as had to cut short tour of Spain and Portugal and limp home. Need to sort before trip to France in June or my beloved refuses to go !!!! Have contacted CSI ignition hoping that a complete system upgrade to electronic ignition may solve my problem. Anyone out there solved a similar experience please.

[Ray White]

Could you have too big a gap at your plugs? This extra strain on the coil can cause it to overheat as the spark attempts to jump the gap.

Also, it is a good idea to earth the distributor.

Check your battery terminals are tight.

Is there a good earth from the engine/gearbox to the chassis?

[Steve Simmons]

I would also suggest testing the coil, or swapping it out for a known good spare. It could have an internal issue. When a coil gets hot, it gets less efficient and if it's weak already, it will cause misfiring.

[jddevel]

Thanks Ray an Steve. Plugs new gaps checked, battey terminals good, new coil best uk produced recommended by club ( begins with "R" not with car and can't remember exact name). Admit not checked chassis gearbox earth since fitting 5speed just over 4k miles ago. Earth distributor ? Never seen that before is it from the clamp to say sump bolt? Reply from CSI suggests possible dwell problem. I believe it's original. Weights recently freed off as sticking. Fault occurred before and since. Might look at new electronic dizzy but will change all leads first incase although solid core recently replaced might be a cause. All suggestions welcome.

[Steve Simmons]

I wouldn't even consider an electronic conversion until I solved the issue at hand. A poor ground or other issue can destroy an electronic device. The points system is far more tolerant of bad power.

I also wouldn't trust anything brand new, no matter the supposed quality. Especially a condenser. If the parts you took out still worked, you may try swapping in the old condenser as an experiment. If that doesn't do it, then try the old coil. Of course this is all after following Ray's advice to ensure power is flowing as it should and all gap settings are correct.

[jddevel]

On route back to the UK. Arriive tomorrow- hopefully then I'll have to go over with a "fine tooth comb" as the sayìng goes. Having successfully completed a 100mile plus trip the weekend before departure thought I'd solved the issue. Obviously over confident. Costly error. Seems so temperature related as was cooler in the UK. I had mentioned in a previous post whilst fully charged my test meter showed over 15 volts at around 2000 plus rpm. Could that be the cause?

[Duncan M]

What coil are you having trouble with? Brand and (primary) Ohms?

CSI is hinting at dwell, which is point gap.

So that is a 45 distributor?

[John Cockrem]

Are you sure you you are not using or trying "modern" coils that require a resistor?
Hope this helps.
Cheers
John Cockrem TC2268

[jddevel]

Not sure John. It was as supplied by Octagon Car Club to replace original fitted when I originally had the problem. Just travelled from hotel to ferry. All OK until queing when although temperature guage showed just below 85. Carbs cool coil hot and once stopped refused to start. Cooled coil with cold water rag. Car started straight away. Shuffling forward to customs stop engine failed to start until coil cooled again.

[Ray White]

I think you have a REMAX coil. There should not be a problem with it. There are a range of ignition coils.
https://www.autoelectricsupplies.co.uk/product_list/316

Is it possible you have a coil that requires a ballast resistor?

Personally,, I would have a word with 'The Distributor Doctor'.. In my experience, Martin Jay has always been most helpful.

[jddevel]

Yes Ray it is a Remax, however it was happening before the coil change which is unnamed and in fact was the reason for the change. As advised will contact Martin after the weekend when we've arrived home. So far a costly experience!!

[Tim Jackson]

A faulty voltage regulator was the cause of failing coils on my early TC, with very similar symptoms (several coils over several years, including Remax). Its been fine since electronic conversion of the RF91 regulator.

[jddevel]

Spoke to the Distributor Doctor -well his wife, who felt that it was a rotor arm fault. Apparently it would appear I currently have a red American manufactured one so new red UK one on order. Did fit one from my TC with same result ( not a red one but it is an original one) However not sure it is compatible. Regarding reference to the regulator as I've mentioed that I believe showing over 15 volts at battery terminals on a fully charged battery does seem strange/ high. I do wonder in my niave way whether it is the cause. Trouble is at the moment I feel as if I' m running around like a headless chicken. It really is so frustrating.

[Duncan M]

It can be frustrating trying to determine what voltage to set your voltage regulator at, using the old Lucas instructions.

Now I simply occasionally check the battery voltage when I return from a drive. Since the last time I fiddled with the adjuster lock nut and set screw it has been reading a bit over 13.5V and all is well. Standard lead/acid battery.

[Ray White]

I don't think the battery overcharge can be the problem because the ignition circuit and charging circuit are separate. Or am I mistaken?

[Duncan M]

All the circuits are being fed battery voltage. If the battery is reading over 15V sitting in the garage, that is too high. Simple adjustment of the regulator. Lead/acid batteries will not last long if they are being overcharged. Not good for the dynamo, either. Many things to consider when sorting a car like the TC.

[jddevel]

OK so fitted new roter arm that Distributor Doctor suggested could well be my problem. Let car idle at 2000 rpm for about 15/20 minutes by adjusting carb. Engine temperature gradually rose to just below 85 degrees ( outside temp around 19/20 ). Coil gradually heated up until very hot to touch but engine seemed to continue OK on fast tickover. Reduced engine speed to around 800 engine stopped. Then failed to start again until car had stood for around 20-30 minutes and coil had cooled. My view- it's not the roter arm!!

[Duncan M]

The original coils on TC's were 4.2 Ohms and tended to not run hot at all. Typical coils are 1.5 Ohms, though 3 Ohms are also easy to find. They look the same from the outside. "Modern" coils can be even less resistance, with 0.5 Ohms or 0.2 Ohms.

Ray asked if you are using a "modern" coil, meaning those with low Ohms. Running a 1.5 Ohm coil in a system meant for 4.2 Ohms will cause the coil to heat up. The over 15V is not helping.

[jddevel]

Duncan, that's an interesting point I was certainly not aware of. I seem to remember when I checked across the terminals a while ago it was registering around one Ohm. I'll check tomorrow , but to remind you it's on a 1500 TF. So is the system the same as the TC. If so I ' ll check what's across the terminals on my TC and perhaps if around 4.2 Ohms give it a try. Cheers Jan

[Steve Simmons]

TC and TF are the same. If running a modern coil, get a 3-ohm version.