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Overheating ignition coil
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Fri May 15, 2015 3:33 pm    Post subject: Overheating ignition coil Reply with quote

Any ideas as to why my ignition coil/s over heat.

I have been having issues with the car ever since I changed the engine.
1172 sidevalve to a more modern 1172 sidevalve, E93a to 100E

Have had both fuel and ignition problems.

Last Sundays problems pointed to Condenser, turned out to be an electric fuel cut off switch.

Been running OK for a couple of days.

Had a run to a friends just over an hour and half away.
When I came out to leave it would not start, the coil was covered in oil so we swapped to another new still boxed coil.
On the way home I came to a stop three times, missfire then die,
You could feel the heat from the coil and it was too hot to touch, after about 30 minutes when cooled down the engine would start and run OK for another few miles and then it would die and a hot coil.

I have the condenser mounted on the bulkhead, been like that since 2009,
That is conected to the Neg. side of the coil and the coil to CB on the dizzy.
Ignition switch to coil poss.
The only addition is a feed for the small electric revcounter to the cb side of the coil, that has been disconected on the first stop to see if it might be the cause.

Getting a bit fed up and I need the car next week for a reunion.
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petermeachem



Joined: 23 Sep 2013
Posts: 358
Location: Chichester Sussex

PostPosted: Fri May 15, 2015 4:11 pm    Post subject: Reply with quote

Are you 12v? It's not a 6v coil without the starting voltage change thingy? That would warm it up nicely
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Fri May 15, 2015 4:50 pm    Post subject: Reply with quote

Good point that Peter

The friend I visited, and gave me the coil runs a classic recovery and workshop and is ex Dunham man.

I wonder if he knows my car is 12 volt, a lot of the older ford side-valves were 6 volt.

Will have a look at that later and post the info.

I have been out for a few 'longer' runs since getting the car back on the road, yet to get back without a problem, beginning to think the car has decided it doesn't like it here Crying or Very sad Laughing Laughing
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Fri May 15, 2015 5:30 pm    Post subject: Reply with quote

No hints as to the voltage.
Phone my friend and no Voltage shown on the box either.

All there is on the coil is a raised Badge either CI or IC with made in England around it.
A label with

"COLD START COIL"
"Replacement for Ford"
"Use only on Ford Models with 1.5 OHMS resistance lead"
and stamped on the base "GP9L"

Got another couple of "Known" coils on the shelf will try one tomorrow and see if that gets hot.

Got to get it sorted by next Friday, of to a reunion in Bomber county.
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Penguin45



Joined: 28 Jul 2014
Posts: 381
Location: Padiham

PostPosted: Fri May 15, 2015 6:33 pm    Post subject: Reply with quote

It's a ballasted coil, so it wants to run at 6v. Have a read HERE. Pretty decent explanation.

P45.
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MikeEdwards



Joined: 25 May 2011
Posts: 2463
Location: South Cheshire

PostPosted: Fri May 15, 2015 6:35 pm    Post subject: Reply with quote

I found this comment on a foreign forum about British cars, specifically they were talking about Triumph TRs but that probably doesn't make any difference:

" Coils that measure about 1.5 ohms across the two small terminals of coil require a ballast. If the coil measures about 3 ohms, it doesn't need a ballast resistor."

So that would imply that if yours is a 1.5ohm coil, it expects to be run through a ballast to give it around 6v during normal running, and often a bit more during cranking if your starter supports it. If the coil is generally good, a ballast resistor in series might be a quick way to sort it out.

ETA: P45 beat me to it.
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Fri May 15, 2015 8:13 pm    Post subject: Reply with quote

Thank you for the info.
I know the spare coils on the shelf are compatable so one will be on it early morning, then a trip to the shops and check how hot.

Oh the joys of classic cars, at least I don't need to remove half the front of the car to get at the coil Twisted Evil

Watch this space Laughing
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Fri May 15, 2015 10:06 pm    Post subject: Reply with quote

Why not simply add a ballast resistor and get the benefits of improved ignition when starting the engine?

Dave
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ka



Joined: 03 Dec 2007
Posts: 600
Location: Orkney.

PostPosted: Sat May 16, 2015 6:28 am    Post subject: Reply with quote

It is not that easy to just add a balast resister.
The are two circuits run to the coil, starting and running. The starting part is fed from a separate circuit, so that when the ignition is turned to start the engine, the feed provides an un-ballested 9-12v. When the engine fires, and the key is returned to normal running, the un-ballast is disabled, and the feed runs through the balasted part. This gives a good spark under heavy load when starting, and a safe 6-9volt when running.Some Minis were fitted with this system, and many Fords.
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KA

Better three than four.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat May 16, 2015 9:17 am    Post subject: Reply with quote

ka wrote:
It is not that easy to just add a balast resister.
The are two circuits run to the coil, starting and running. The starting part is fed from a separate circuit, so that when the ignition is turned to start the engine, the feed provides an un-ballested 9-12v. When the engine fires, and the key is returned to normal running, the un-ballast is disabled, and the feed runs through the balasted part. This gives a good spark under heavy load when starting, and a safe 6-9volt when running.Some Minis were fitted with this system, and many Fords.


That's simple to me Smile it's a 5 min job, put the resistor in series with the coil on the switch side, and run a cable from the starter motor to the coil resistor junction ...simples Smile

You don't have to add the cable from the starter motor, but then loose the improved starting benefit.

Dave
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Sat May 16, 2015 11:53 am    Post subject: Reply with quote

So far so good.
Just fitted a standard 12V coil this morning, had it running for about 20 minutes.

Just remeber this car is as basic as one can get,
Ignition, charging and lights is all there is.
Oh and a klaxon.

I wonder if the first coil might have been damaged when the Fuel cut off switch played up, it was conected to the ignition via the pos. side on the coil.

out to the shops after lunch, the long way round, I'll check how warm the coil is when I get there.
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Sat May 16, 2015 8:19 pm    Post subject: Reply with quote

Been out for about an hours run with a few hard blasts.

Coil was a bit warm but at least I could hold it, How warm do they normally get.

Might move it to another position,
Since I fitted a manifold heat shield It might have changed the airflow, it dose seem to be warm in that area, just behind the cylinder head
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sun May 17, 2015 1:07 am    Post subject: Reply with quote

Roger

The only electrical / ignition factor that would normally affect coil temperature, is the dwell time, which is regulated by the points gap.

If the coil is getting unusably warm, it may well be location.

Dave
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Peter_L



Joined: 10 Apr 2008
Posts: 2680
Location: New Brunswick. Canada.

PostPosted: Sun May 17, 2015 2:03 am    Post subject: Reply with quote

Roger. Just a thought, Put your voltmeter on the battery with the engine running and lift the speed to running rpm. Just to check that the voltage is not going abnormally high. About 13.5 I used to think was about right.

Strange that human nature will make something feel warmer or colder when the item is in doubt, whereas when all is OK, whatever it is, is acceptable.
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ka



Joined: 03 Dec 2007
Posts: 600
Location: Orkney.

PostPosted: Sun May 17, 2015 6:52 am    Post subject: Reply with quote

I am sure everyone will agree, there are some dodgy Dizzy caps, rotor arms, condensers and coils out there, even NOS. Difficult to tell them apart until they fail.
Keep us informed how things are going, and yes a slightly warmer coli is not unusual, as said, it all depends on the temperatures you are contrasting it with.
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KA

Better three than four.
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