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MG TD TF 1500 - Hot coil

Hey guys,

I had one of those moments last night when the car stranded me! Flat bed home :( It was running fine when I stopped at the pub, but when I tried to leave she wouldn't start. It was turning over but would not fire. Anyway when I got her home I tried and tried to get it started. I noticed the coil was very warm. I could hold my hand on it but if it was any more warm I would not of been able to. Far as I know this is the original coil from 52 or at least 1965. It might be time to replace the coil. Is it normal for a coil to get this warm? Funny thing is I did get it to start last night, and this morning it fired on the first attempt! 1952 MG TD.

Thanks,

Rich
Rich King TD 8732

Sounds like your coil is on the way out. When it cools, it gets fire.

You have some choices: an Abingdon Spares copy of the original Q12 coil, or a Lucas Sports coil. The black, original-style should last a long time, but the Lucas, while not original looking, will give a hotter spark.

Tom Lange
MGT Repair
t lange

The original style coil will accept your existing HT lead. The sport coil will require a new push-in lead. (Or a shop made adapter.)

Jim B.
JA Benjamin

Check your points gap, the smaller the gap the longer the points stay closed and the hotter the coil gets, they do run fairly warm , about as you say, hot to touch but holdable
William Revit

Thanks guys
Rich King TD 8732

Actually another couple questions. As JA mentioned above I see the coils Moss Motors offers require a push in wire lead. I currently have bumblebee ignition wires. The bumblebee wires feature a multi strand copper core. Do I need to replace them all or just the lead going from the distributer to the coil? Also I see listed in the description for the coils Moss offers there is a non-ballasted system. I am not sure what that means?

Thanks,
Rich


Rich King TD 8732

The other, spark plug, wires are fine.

Just replace the coil wire.

In order to maintain some originality I made an adapter.
Drawings available.

MGT's did not have ballasted ignition. These hav an external resistor in series with the primary of the coil.

Jim B


JA Benjamin

Rich

This is the Moss coil with the screw in HT connector. I got one a while back. A bit spendy for a coil but it’s ‘correct’ for the car. I think it also comes with the connector to put on your wires if yours is broken or lost.

https://mossmotors.com/coil-screw-type-h-t-connection?assoc=27967

Maybe get a cheap coil to test out and then get this one if it turns out to be the problem.

Stuart
S Grimm

Many years ago a buddy was powering an electric fuel pump from the hot side of the coil. This caused the coil to over heat and would leave him stranded until it cooled off. He relocated the pump power and problem was solved.
rich40701

Pump is hot. but think of coil cooling system. Mainly conduction through scuttle.
A large support bracket, well tightened. Good thermal contact with the scuttle. I added thermal compund between coil and bracket.
Think of oil convection in it also. The hottest part of the coil is the upper part so position the clip on this upper part. Not the very top because ther might be a bubble on the very top if it is not full of oil.
But anyway, the symptom is a dead coil. The oil is oxydizing or missing. Hence internal arcing when hot.

Laurent.


LC Laurent31

I am having some difficulty locating a solid core wire. I am wondering if what I think a solid core wire is incorrect. I assume a solid core wire is one thick wire, not multi-strand. Is that correct? I see some wire listed online as solid core but the picture sure looks like multi-strand to me. Thoughts?

Rich
Rich King TD 8732

Rich, 'solid core wire' refers to the wire that's inside of the bundle. Generally, it's multi-strands of solid wire inside of the bundle. The 'non-solid wire' is made up of multi bundles of things like powdered-carbon-impregnated strands inside of the bundle, not wire. Hope this helps. Bud
Bud Krueger

So I was sizing up what should be a quick/easy coil change out on the car. I am running an original Lucas coil on a positive ground car. The terminals on the old coil to be replaced are labeled as SW and CB. The new coil is labeled as +/-. I assume that the #16 wire (color unknown) from the side of the distributor to the new coil go to the (+)positive side of the new coil? And the #9 (white) from the wire harness/battery feed go to the (-)negative side of the new coil? If not I am really confused. This positive ground stuff can really be confusing. Also since I am replacing an original coil with a pertronix. I noticed the Pertronix is about 1/8 inch larger in diameter. Anyone know if this will fit in the factory coil mounting bracket? Or was the original mounting bracket spot welded to the coil? I can not remember.

Thanks everyone,

Rich



Rich King TD 8732

Your thinking on the wiring is correct
Pos. side of coil goes to the dist
Neg. power feed from ign. goes to Neg.
William Revit

Rich, as I read your posting I'm assuming that it is only the coil that you're replacing with a Pertronix product, not the points? The reason that I ask is because the positive ground Pertronix Igniter is wired in a very different manner from ordinary distributor wiring. Bud
Bud Krueger

Yes Bud, at this time just the coil. I would however like to change over to the electronic ignition some time soon.

Rich
Rich King TD 8732

Rich
Just make sure you have the correct coil ,it should measure approx 2.5-3 ohms accross the two primary terminal posts (+ -)without any wiring connected

Don't take someones word for it ,measure it or get it measured

willy
William Revit

Rich, if you switch to the lobe-sensing version, LS-numbers, you'll need to change wiring from solid-wire to a 'modern' non-solid wire. The LS doesn't use the magnet collar, it senses the lobe on the shaft. Bud
Bud Krueger

I finally got off my duff and switched out the coil today. It was pretty painless has a whole. I thought the push in clip/wire type would hold inside the coil better then it did. It seems like it is really just the boot that is holding the wire in place. Does that sound about right or did I do something wrong?


Rich King TD 8732

"Or was the original mounting bracket spot welded to the coil? I can not remember." I just dug out the original Q12 coil that was in the car when I bought it in 69. The bracket is spot welded to the coil. I just gave it a wire brush, sanded, primed and hit her up with some satin black. See pic. Cheers
Peter TD 5801



P Hehir

Anyone know the thread type/size on the original Q 12 brass terminal studs? Mine is missing a couple of brass nuts. Also any washers originally? If so what type, thickness, size, material, what went where originally etc.? Cheers
Peter TD 5801
P Hehir

Rich when you are ready my Abingdon Performance Ltd. is the only USA CSI (Custom Sport ignition) dealer that offers and stocks CSI distributors for MG T types, with or without a vacuum advance. Special curves for XPAG S/C / vacuum advance applications.
Len Fanelli
Abingdon Performance ltd


Len Fanelli

Peter

Best guess would be 2BA Brass Hex Nuts, usually a brass flat washer either side of terminal.

Maybe not the way it was done during production however if you want ignition reliability I would be slipping a stainless spring washer into the mix.

Graeme


G Evans

You're on the money Graeme. It's just been confirmed from two different sources offline. Thanks mate. Cheers
Peter TD 5801
P Hehir

This thread was discussed between 11/07/2020 and 18/09/2020

MG TD TF 1500 index

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