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MG MGA - Failing Coil

Over the last year or so my starting has got more and more difficult despite it running well once started. Then following my rather hot recent engine issue the coil failed. I got a new coil and now the car starts as instantly as you would expect even in this weeks temperature. I had always thought coils always worked or didn’t but clearly not. By the way both coils involved are the up market Peritronix Flame Thrower.

Paul
Paul Dean

Yes I also thought that either they worked or they didnt. Either there is a break in the coil, or there isnt. I imagine that over the years the insulation on the wires in the coil can start to detioriate causing some short circuiting?
Graham V

I used to run my 1850cc 3-bearing MGB engine with an electronic pertronix distributor and the matching Flamethrower coil.

I did have a couple of Pertronix distributors fail on me and I also had a flamethrower coil develop an oil leak, although it never actally failed.

My present 1950cc 5-brg engine came with what is marked as an "electronic MGB Race distributor (it has no makers mark though) and a modern replica Lucas Sports coil.

It does go very well and it certainly gives a strong spark, which I found to my cost when I pulled the plug lead off recently to find out which one of the spark plugs was mis-firing.
It was a sort of an accidental de-fibrillation experience :^)

So, I am inclined to think that you probably don't need the so called high performance coils on an B-series engine, no matter how highly it is tuned.

Cheers
Colyn









Colyn Firth

Coils have got a mind of their own and can have some weird symptoms
Had a 2litre Escort once that would missfire going round right hand corners (roundabouts), checked all the wiring .fuel lines , everything and it ended up being the coil---------but only to the right, left turns were fine
William Revit

Something to do with politics in there Willy!
Barry.
Barry Gannon

There seems to be two schools of thought, one that coils suddenly fail and the other that any ignition or running problems the coil could be the issue. As it's difficult to see how it's working and the item is low priced often they are swapped out for new or known good one. Retainers of old replaced parts normally have a coil or two.

I've swapped a good working coil for a new one a couple of times as I'm lazy and don't like getting my hands dirty. I've even been offered the loan of the part from a mate as he'd kept the old one I gave many years before as a carried spare on his car. It confirmed that one and the one fitted to my car made no difference to the problem I had.

Lifted from elsewhere. -

"Coil problems are caused by heat and vibration. It is possible to have a sudden failure due to broken windings or bad connections inside the coil. However, it is more common for coil problems to show up as hard starting, a repeated high-speed miss or a gradual decline in ignition system performance."
Nigel Atkins

Coils usually fail gradually in my experience, but do also fail suddenly sometimes. The normal symptom of a coil going bad is that the car runs worse as it heats up. When I test coils, I first test them cold and then hot. The hot spark output is always weaker, even on a good coil. I've seen some coils that sparked strong when cold, and barely anything when heated.
Steve Simmons

I presume the reason MG moved the coil from the top of the dynamo to the inner wing was to get a cooler position? As mine is still on the top of the dynamo I will now move it to inner wing. Thanks for all comments.

Paul
Paul Dean

Paul,
others will know better than me but I'd not bother moving your coil as they seem to work well for many years (decades) in lot hotter engine bays. But then if summer 2023 and beyond are going to be the temperatures of summer 20022, 40.2c here, then perhaps as Tesco tell us every little helps.

I've been trying to promote that the extreme hot weather we had wasn't good for car batteries (and charging system) on classic cars but particularly modern cars with all their electric demands and stop/start systems and this will be reflected in even more battery issues (often use, abuse and neglect from the drivers) now the winter is with us. The Xmas and New Year activities and lack of will bring another wave but early or preventative external (battery charger/maintainer) use has fell out of practice last x-decades.
Nigel Atkins

Heat and vibration aren't good for coils, which is why they were moved off engines for the most part in those days. I left mine on the engine for originality and haven't had any issues, but I accept that the vibration will probably kill it sooner.
Steve Simmons

This thread was discussed between 21/12/2022 and 23/12/2022

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