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MG MGB Technical - Bad parts keep you fit !

I took the B out this afternoon for a winter warm-up and after about 2-3 miles and it started miss-firing, particularly on acceleration, and 500 yards from home cut dead and would not restart. So I had to push it home, over several speed humps. That’s the fitness bit.

The bad parts bit. The cause of the problem was that both of the spring clips, which hold the distributor cap on, had punched two holes right through the cap; see picture. When I changed the cap everything was back to normal.

Obviously the ingress of the spring clips created an effective intermittent path to earth for the HT. I suspect that the cap broke when I refitted it prior to my run after having wiping it out to remove any condensation that may have accumulated there over the last two months.

I’ve never seen this fault before and I put it down to the distributors cap’s plastic being too brittle. I now need to reset the timing as I had to remove the distributor to extract the plastic debris.

Has anyone else experienced this ?

Richard.




Richard Thompson

Possibly not helped by regularly driving over speed bumps.

It seems that you can't rely on any new parts, these days. Things have got so bad that I now don't throw any old parts away.

An unfortunate consequence of this is that I am now renting two lock-up garages to keep all the parts in!
Dave O'Neill 2

Years ago one of the speed shops here were selling clear plastic dizzy caps-I put one on my B
Unbelievable to open the bonnet in the dark and watch the spark activity in there. Eventually it died in the same area as yours, where the clips go, but it actually melted two holes through to the clips---Plastic a bit too soft I guess
willy
William Revit

The cap that I fitted to replace the broken one is 10+ years old which I removed as a part of a routine service. The broken one was sold in a Lucas branded box but I'm aware that this does not mean that Lucas actually made it.

R
Richard Thompson

Who is Lucas? It's changed hands a couple of times at least via American owners, and they can authorise anyone they like to manufacture parts and put the Lucas name on the box. It's like Cadbury's chocolate. The American owners have authorised Hershey to manufacture a poor imitation with 'Cadburys Dairy Milk' on the wrapper, for sale in America, which tastes nothing like 'the real thing'. This has lead to specialist 'English' shops there importing the proper stuff from England, and Hershey are suing Cadbury (American owners remember) for 'unfair competition'.

I've not seen one break up like that, but a pal a year or so back did 10 miles on a new one before the centre contact and spring disintegrated.

Where did this come from? I'd be interested to hear of any problems with stuff bought from the Distributor Doctor, or Simon BBC, and what response they got to a complaint.

Paul Hunt

dissy caps like rotor arms seem to be available in p*ss poor or good quality (like many other parts)

last year I bought a (2004 stock) 'Lucas' dissy cap that looked like it had varnished copper terminals inside and out and decided I couldn't trust to fit it so returned it

I got it's replacement from Simon BBC (Powerspark) and that was fine

Accuspark's website has it that they use Distributor Doctor's rotor arms

good quality CB points I've lost track of

but for very good quality sturdy HT lead sets you can buy retail from the original manufacture via their website and phone order from 'performanceleads' (Fastlane Auto Ltd) - http://www.fastlaneauto.co.uk/
Nigel Atkins

This thread was discussed between 14/02/2015 and 15/02/2015

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