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MG MGA - Condenser Failure/Good Trip

I will come back to the attached photo. I fitted a new Moss distributor last week to my new to me 3 bearing B engine. After around 200 miles the car suddenly stopped, had a look around then after about 10 mins it started OK, and then the same thing happened 3 more times. I have now changed the coil then condenser (known good one) and all seems OK. Obviously this sounds heat related and I know that new condensers can fail but the question is it likely that a distributor fails on an engine at normal running temperatures and then when it cools a bit starts working again several times over?

I was on a 'running in' trip this week for the engine and passed 500 miles mark at the top of Glencoe in glorious sunshine. We then went over the Corran Ferry and hence to Ardnamurchan. Photo shows the A at Ardnamurchan Point which is the most westerly point in mainland Britain, very remote. If you are interested in mountains/islands the background is the Scuur of Eigg and the Cuilins of Rhum (not the Skye ones that were out of shot to the right).

Problems started the next morning a few miles before the ferry but with time, and help from the ferry's mechanic, we got across to the less remote east shore and then called the RAC who via the local garage tried to sort it but knew nothing of pre-computerised cars resulting in an eventual relay home. I did have spare condenser but I didn't want to risk leaving the garage and then fail again in a few miles!! Also of course I also thought a brand new one wouldn't, but then I read Barney's site.

Comments welcome to help me get my confidence back. Before anyone mentions it this wasn't fuel vapourisation.

Paul



P M Dean

Have you tried changing the rotor arm? I had a very similar experience with a TR6 which in the end was a poor quality rotor arm. If you buy a new one get it from the Distributor doctor, his are very good.
p anderton

Paul
To test the rotor arm take of the dizzy cap and disconnect the coil lead at cap. Hold lead over the brass strip on the rotor and fire the coil. If you get a spark then the rotor is u/s and the spark is earthing through the rotor and down the dizzy spindle. No spark is good.
Basically increased use of graphite for blackening and over long rivets cause problems with rotor arms so get a red rotor from dizzy doctor.
Alan
Alan Anstead

Symptoms could equate to distributor cap - it's often not possible to detect a crack. Try running engine in totally dark garage.
J H Cole

Afraid not as I have tried the rotor that I had been using before last week and fine. I do think I have probably solved it with going back to old condenser in new dizyy but does my intermittent symptom theory of the condenser failing and then coming back make sense?

Paul
P M Dean

Well I had a similar situation in my B a few weeks ago. Runs for 15 mins or so and then stops and won't restart. Leave for 30 mins and all is well for the next ten mins before stopping again. Swapped coils believing this to be the culprit but no change. Fitted a new condenser and all now seems to be well. I keep my fingers crossed. This seems to be the same situation you had Paul and I guess that it is fixed
Iain MacKintosh

I will come back to the attached photo. I fitted a new Moss distributor last week to my new to me 3 bearing B engine. After around 200 miles the car suddenly stopped, had a look around then after about 10 mins it started OK, and then the same thing happened 3 more times. I have now changed the coil then condenser (known good one) and all seems OK. Obviously this sounds heat related and I know that new condensers can fail but the question is it likely that a distributor fails on an engine at normal running temperatures and then when it cools a bit starts working again several times over?

I was on a 'running in' trip this week for the engine and passed 500 miles mark at the top of Glencoe in glorious sunshine. We then went over the Corran Ferry and hence to Ardnamurchan. Photo shows the A at Ardnamurchan Point which is the most westerly point in mainland Britain, very remote. If you are interested in mountains/islands the background is the Scuur of Eigg and the Cuilins of Rhum (not the Skye ones that were out of shot to the right).

Problems started the next morning a few miles before the ferry but with time, and help from the ferry's mechanic, we got across to the less remote east shore and then called the RAC who via the local garage tried to sort it but knew nothing of pre-computerised cars resulting in an eventual relay home. I did have spare condenser but I didn't want to risk leaving the garage and then fail again in a few miles!! Also of course I also thought a brand new one wouldn't, but then I read Barney's site.

Comments welcome to help me get my confidence back. Before anyone mentions it this wasn't fuel vapourisation.

Paul



P M Dean

Have you tried changing the rotor arm? I had a very similar experience with a TR6 which in the end was a poor quality rotor arm. If you buy a new one get it from the Distributor doctor, his are very good.
p anderton

Paul
To test the rotor arm take of the dizzy cap and disconnect the coil lead at cap. Hold lead over the brass strip on the rotor and fire the coil. If you get a spark then the rotor is u/s and the spark is earthing through the rotor and down the dizzy spindle. No spark is good.
Basically increased use of graphite for blackening and over long rivets cause problems with rotor arms so get a red rotor from dizzy doctor.
Alan
Alan Anstead

Symptoms could equate to distributor cap - it's often not possible to detect a crack. Try running engine in totally dark garage.
J H Cole

Afraid not as I have tried the rotor that I had been using before last week and fine. I do think I have probably solved it with going back to old condenser in new dizyy but does my intermittent symptom theory of the condenser failing and then coming back make sense?

Paul
P M Dean

Well I had a similar situation in my B a few weeks ago. Runs for 15 mins or so and then stops and won't restart. Leave for 30 mins and all is well for the next ten mins before stopping again. Swapped coils believing this to be the culprit but no change. Fitted a new condenser and all now seems to be well. I keep my fingers crossed. This seems to be the same situation you had Paul and I guess that it is fixed
Iain MacKintosh

I tried the test in the dark last night and no arcing.

Iain's situation sounds identical and I first suspected the coil and changed it for an old one I carry. The garage hunted for another coil then phoned a guy 'up the village who did old cars' and he appeared with a shoping bag full of them and we tried a third but still stopped after a while. I have ordered and will fit a new coil but I think it is the condenser that has fixed it. Perhaps I will do Barneys coil test on the failed one at different temperatures.

Of course seeing Iain's location perhaps it is Highland fuel? It certainly wasn't the dreaded Highland midges though blocking the radiator as there were none around, whereabouts are you by the way. Home for me is North Queensferry.

Paul
P M Dean

Get a condenser and a red rotor from Distributor Doctor. I had a lot of similar trouble with my B, and kept changing condensers. Then one day I opened one of them, see the attached photo.

These parts are supposed to be soldered together, but as you can see they are not. The inside was just rattling around, giving very intermittent contact. I replaced it with a DD condenser, it works perfectly.

The rotor is a bit different. When the rotor goes, it goes suddenly, and there is no way back. One day the MGB of a friend just died, like someone switched off the ignition. We went through every single component of the ignition system, using instruments, including changing his new electronic distributor for another one.

Finally the only component left was the rotor. The electronic distributor used the original rotor. I had a spare red DD rotor in the B, we put it in, and it started immediately.

Many of the ignition components sold today by the big dealers are crap. Distributor Doctor makes quality components. And no, I don´t have shares in his business!

Tore

Tore

Following Tore's photo I have done the same with my suspect unit off my BRAND NEW distributor. It is exactly the same at the end he shows and at the other there is just a dimpled disk between capacitor and the end of case. There is also a dark mark at this end which is probably caused by bad contact. Basically they just depend on end to end pressure of the case to make the contacts, then they expect them to work in the relatively hostile temperature and vibration environment of a distributor. I suspect the case expands faster than the capacitor itself hence fails when warm then comes back as it cools. The externals of the unit look good quality with a neatly crimped lead but the whole thing inside looks rubbish.

The one I have now fitted and working in the car came out of my old 1500 unit that I have used from my 1979 rebuild until last week. I suspect it was either on one of my cars when I bought them (1969 and 1972) or is an early 1970s replacement (when I was doing 30k miles a year) hence probably is a genuine Lucas unit. It would be interested to know what the original one is like inside but obviously I am not going to destroy that one.

I will be calling Moss in the morning, and getting a spare from DD.

Paul
P M Dean

Ironic that so many folks on this forum absolutely hate
the pertronix electronic dizzy components, and then complain that supplied condensers for standard points, are , basically , crap.....
Yes, I carry a spare Pertronix, but , (knock on wood), in four MG's, have never had a failure, nor needed to use the spare...
My advice, if it happens again , switch to Pertronix, and buy a spare for peace of mind.

I also support the use of the red rotors, since the new black rotors are junk.

Edward
Edward Wesson 60MGA

Paul,
To answer your question, yes condensers can fail when they get hot and work again when cooled down. So just replace it. Looks rather as if you have discovered why now... Coils can also fail when they get hot probably because there's an internal short in the coil causing the overheating. I don't believe a bad rotor would fail when hot and work again when cool.
Pete
PeteT

Interesting development.

Firstly car now running. Had lovely 60 mile test run, well except for finding around a corner a road covered in deep farmyard 'muck'.

The main point is to report on my conversation with Moss the other day. I rang them to mildly complain about the condenser in my brand new distributor very inconveniently failing after less than 200 miles. I explained that I had opened up the failed unit and was not impressed, or surprised it failed. I wasn't particularly after anything as I now have 3 spares, after all they only cost around £2. I was told that the new ones I had bought would be of similar (poor) quality as the one that had just failed and what I needed was the 'High Quality' unit, i.e. GSC111HQ rather than just GSC111. I said that I had never seen this in either on line or paper catalogue. I was now feeling like complaining and thought my defective/low quality ones should be exchanged. I was told that I could only do this by email to R&D, After more grumbling he offered to put me through to R&D, the extension was not answered, and I was asked to ring back the R&D number. I felt selling defective goods was really a sales issue and it was his business to report to R&D, eventually he agreed to send me a free GSC111HQ, I then negotiated a second one as I had just been delivered 2 standard ones.

I have now got the GSC111HQs and the zero value invoice shows the unit price as £7.31. The only visual difference is that the lead is soldered to the external connection and presumably then has a solid connection to the capacitor inside. Perhaps I should open one up.

The HQ unit is still not in the catalogue so how you are supposed to know this is the one to order I don't know. I would be very happy to pay 3 times the price, £7, for a condenser that works on a car worth MGA prices. Why do the sell the others, and sell distributor with defective ones inside?

Paul

P M Dean

This thread was discussed between 16/05/2014 and 22/05/2014

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