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MG Midget and Sprite Technical - Dodgy distributor cap and burned out lead mystery

There's no mystery about the dodgy distributor cap - lasted less than a year and I know there has been some discussion on cheap Chinese electricals (not that it was cheap).
The symptoms were occasional misfire, then loss of ignition. Then it was fine for bit but when left running it would suddenly stop and then not start again. No sparks.
Swapping to a known functioning distributor cap and leads had it running perfectly, but a closer look showed that the old coil to distributor HT had burned through - melted core and sleeve - and was only making sporadic sparks.
Two questions: What would account for the 11-month-old silicon lead disintegrating? Could it be the cap internals?
Secondly does anyone know where I can get hold of a top quality side entry cap and leads, Lucas or better? I'd rather pay a couple of quid extra to have less chance of it failing again.
Thanks
Crispin (IoW Healey Frogeye)
C Whiting

http://www.distributordoctor.com/

I haven't used him (Yet) but this chap comes highly recommended and refuses to sell any rubbish.
Mike Howlett

One disintigrated on me in less than 11 minutes :( It wasn't a cheap import either .....!
rachmacb

Crispin

Is your distributor a 25D or 45D?

I have some side-entry caps for the 43/45D
Dave O'Neill2

Crispin.
I use Distributor doctor parts - red (brown?)dizzy caps and red rotor arms. No complaints to date. Fitted them to other peoples cars too!
Alan
A Anstead

Not sure if mine is a 25 or 45, but found a good genuine Lucas cap still boxed in the shed which would have been for my old L-reg midget or one of my wife's Morris Minors. Running beautifully, but sounds like a good idea to pick up a spare red/brown one from Distributor Doctor. I assume these have no carbon colouring and are less likely to arc out. Aleady using a red rotor arm.
Thanks for the suggestions.
C Whiting

Hi Crispin

Pleased you are running OK again

What caused your problems?

Well firstly you can not blame the Chinese, they make EXACTLY what we ask them to make it is not necessarily what they would prefer to make. The distributor doctor products are a good example they are cheaply made products but have been redesigned to avoid problems. I think the biggest problem with the rotor arm was the rivet, this has now been engineered out and the blade is glued on I believe?

So we can now find parts that work which is a good thing

What about your issues?

The coil lead could have burnt for a couple of reasons.

1. do you have a sports (high power coil) coil on an ignition system designed for use with a balasted coil?

2. and the more likely a poor joint at the distributor cap to the coil lead would cause excesive heaing and would/could burn the end of the lead.

HTH
Robert (Bob) Midget Turbo

For a 45D side entry cap: BMC sherpa designated fits. Remove the screws from the cap and just use the clamps. Could post numbers if required, but right now I'm at work (mwoa, kind of)
Alex G Matla

I'll also vouch for the Distributor Doctor....

Mark.
M T Boldry

Blimey! Perhaps I do have sports coil fitted to a system designed for a balasted coil. It is gold in colour (as was the one it replaced) which might hint at that. Sold to me as ideal for the standard 1275 setup by an mg specialist though with no warning that it might frazzle leads.
Don't think the lead to coil was a problem - quite a tight fit although the coil did recently slip slightly in its band under tight cornering and pull the lead out through centrifugal force. Impressive cornering or what. Tightened up the band, obviously, and that was about a week before the HT burned through.
Perhaps I should go back to a standard coil and keep the gold one as a spare.
Anyway, it's running beautifully now.
Thanks for all the suggestions.
C Whiting

This thread was discussed between 02/12/2011 and 07/12/2011

MG Midget and Sprite Technical index

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