MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Plug leads

My car has been starting badly recently.
It starts on only 3 cylinders until there is a bit of warmth , about 30 sec to a minute from cold. OK when hot.
So I was trying to find which cylinder was the problem by starting and pulling leads in turn while it was running rough.
Found it was No 3, but in doing so I was getting shocked even though I was holding the leads with a rag.
The leads are about 5 years old. I don't know if they behaved like this when new as I never tried pulling leads then.
Plugs all looked pretty good after about 6,000 miles.

Is it normal to get shocked through a lead ?
Art Pearse

Its pretty much par for the course to get the 20000 to 50000 volts go through your arm when you pull a plug lead. The voltage has to go somewhere.
It shouldn't do you any harm ( unless you have a pacemaker installed!) but it is always unpleasant.

You need to use some VERY well insulated pliers to pull the lead off the plug and then immediately put the plug cap onto (or very close to) something like a head bolt so that it can spark safely through it.

I believe that some high performance ignition coils can be damaged if you disconnect a lead whilst the engine is running.

You could first try a new set of plugs, then if that's no better, fit a set of new ignition leads.
This way you are gradually eliminating the possible causes, one by one.

Cheers
Colyn
Colyn Firth

I've had a rotor arm fail by inadvertently running the engine with one lead disconnected. That was with Lumenition electronic ignition.

I'm sure that Willy will be along shortly with a warning of the health hazards of HT leads.
Dave O'Neill 2

I have had this in my tool box for more years than I care to remember. Saves all the pain. Just plug it in to a lead and spark plug. Fire up and watch the spark - or not.

Steve

Steve Gyles

Ahh - my favourite subject

Colyn---your statement----

"It shouldn't do you any harm ( unless you have a pacemaker installed!) but it is always unpleasant".

wrong - and poor advice - I acknowledge that you went on to say to use insulated pliers but to say it shouldn't do you any harm is dangerous territory -
It initially cost me 18 months off work and has now ended my working days - and income

BE CAREFULL

Dave --It doesn't need to be a powerfull ign. system to do that either - a mate had a lead fall off his stock std. TC and it did just that before he had time to pull over to put the lead back on

Steve
I made one up out of an old spark plug which I have always used , but got a bit complacent and paid the price - big time-!

Art
Maybe it's a possible that your ign. points gap has closed down or maybe valve clearances need checking


William Revit

Wow, I'm so sorry to hear that Willy!

I must admit that this is (until now), the first I have heard of anyone suffering any serious health problems through getting spark plug voltage through their arm.
Can you give us any more information about the exact dangers? It could be very useful for us all to know.

Maybe now that I am well into my 7th decade I had better be more careful about pulling my ignition leads with the engine running!

Yours (and Steves) spark-tester look to be a lot safer option.

Cheers
Colyn
Colyn Firth

For me too this is the first time I've heard how serious this was for you and sorry to hear it.

As a very young lad for reason I can't remember now I had the back off a radiogram (remember those) and put my fingers on the fuse inside which involuntary threw my arm back, a shock in more ways than one, but it made me very respectful of electricity in all its ways and literally makes me keep my distance (and protection) from it as much as practical.
Nigel Atkins

Used to toast bread on a fork using a 240V bar fire.
More than once got too close to the element!

I wasn't aware of a HT coil causing actual bodily harm
Must be more careful!
Art Pearse

I recall getting zapped by a frayed spark plug wire back in high school days. That shock traveled right up my arm and sent me back. Perhaps if I was wearing sneakers (trainers to you) instead of leather soled shoes, it would have been less severe.

Cheers

Gary
79 MGB
gary hansen

Hi
I don't really want to go on about me, what happened to me was my fault and mine alone.
I've spouted out more personal info than I intended to---thanks for your thoughts all the same. Much apreciated- This forum always amazes me that we can feel for people that we only know from here really-
On the plug lead issue-
Years back coil output was probably around 20,000V and yes a boot up the arm was just that, a boot up the arm. -I can remember getting some ripper hits setting up impulse magneto timing, where it would flick over and bang gotya--still dangerous but at a lesser degree
BUT nowadays ign. coils can poke out 50-60,000V and higher amperage to go with it.
So--- if you're going to pull leads with the engine going, which is sometimes the only way to diagnose a particular fault, please, please get youself a pair of plastic pliers to do it and live to talk about it
The insulated electricias pliers aren't so suitable, on older cars you might get away with them but on anything with a decent coil you should have full plastic or fibre pliers
And--with most coils, and moreso the later solid state high output coils, if you're pulling a lead to check for a spark or misfire, don't pull it right away from the plug, just far enough to see or hear the spark jump is all that's needed--If you pull it right away from the plug with these coils the spark has nowhere to go and is that strong it goes straight through the insulation of the coil and wrecks it
William Revit

Willy,
I've always thought you were a bright spark but now I've changed my mind seeing you allowed yourself to be abused by Ford products!

You light up my life, if only you looked liked Debby Boone.

Nigel Atkins

lol-Nigel
Ford eh, -you been doing some homework-?
William Revit

No Willy, just the 'craft plug in the welded nipple-clamp photo you put up earlier.
Nigel Atkins


I have just been thinking about a gadget that I have at home that was passed down from my grandfather. It is designed for medical use and it consists of a beautifully made hardwood box containing an Induction Coil and various hand held pads and hand grips.

IIRC correctly, it is from Edwardian times and it was designed to apply high voltage AC to various parts of the body to treat arthritis and rheumatism etc.

It is powered by a single 1 1/2 volt torch battery voltage output was controlled by the gradual withdrawing of an iron rod from the coil centre.

I remember the output could be ramped-up so that all your arm muscles would spasm and your hands would claw.

Heaven knows what voltage was being put out by that thing!

I think I will leave it in the box from now on!

I will post a picture when I manage to remember where I have stored it :^)

Colyn



Colyn Firth

This is the first I've heard of someone being hurt by a plug lead also. Yikes! I've been zapped too many times to count but never did anything more than startle me. The worst one though, was when I got hit by a magneto from a WWII pull crank engine as I was spinning it over. That one hurt. I don't do work on modern vehicles if I can help it but I'll certainly watch out for that higher voltage if I do. Biggest coil I have on my own cars is 30KV.
Steve Simmons

I was wondering if Colyn's gadget was an Edwardian vibrator.

. . . I'll get me coat.
Nigel Atkins

Came across this tool in my old stuff a couple of weeks ago. I think it's relevant to this thread. It's something like fibrous bakelite and embossed "Safe-T-Grip." It's manufacturer is Ideal Sycamore of Illinois, USA. I think it's for safely pulling spark plug leads of the plug or handling other high tension wires. Could be something else altogether but that's my best guess.

Jud

J. K. Chapin

Nice -Jud
They look like the plug lead pliers that came with my old 'Sun' oscilloscope years ago
Worth their weight in gold---------
Keep them and use them-

willy
William Revit

Nigel,
I somehow think that the idea of using 20,000 to 50,000 volts A/C to "Spark-Up" your relationship wouldn't be so well received, that is, unless BDSM was your thing! :^)

More likely to to leave someone "Spark-out!"

I still can't find the antique induction coil but I have found a link to a similar one for sale on Ebay.
https://www.ebay.co.uk/itm/Antique-Victorian-Induction-Coil-Medical-Electric-Shock-Machine-Nervous-Therapy/202659747965?hash=item2f2f76587d:g:hdYAAOSwKVtcvfDL&frcectupt=true

Cheers
Colyn
Colyn Firth

It was a dud plug on cyl 3 !
All OK now
Art Pearse

Thanks for reporting back.
Nigel Atkins

This thread was discussed between 03/06/2019 and 16/06/2019

MG MGA index

This thread is from the archives. Join the live MG MGA BBS now