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 Missing spark 
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2CV Fan

Joined: December 27th, 2011, 9:50 pm
Posts: 85
Post Missing spark
Hi all.

Thought I'd share 'The case of the Missing Spark'.
My '86 Charlston always starts on the button, that is until recently when on damp mornings there is no spark. It's gone awal. A short time later and it usually starts.

I have done the obvious, cleaned, dried all connections under the bonnet relating to the ignition. Tried another coil.

I then thought to look further so I took off the fan and looked at the points box.
The underside of the box was completely covered in old road dirt/engine oil and general crap. It covered the capacitor and the feed connector to the points.
I cleaned it all and now await the next damp morning to see if that was the problem.
I'll keep you posted.

ps. The car has a Boyer points assist and was reassured that the points, after several years, still look pretty new.


October 15th, 2020, 6:00 pm
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Joined: February 22nd, 2012, 10:34 am
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Post Re: Missing spark
What about the Boyer box itself?
Is it dampproof?

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October 15th, 2020, 8:30 pm
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2CV Fan

Joined: December 27th, 2011, 9:50 pm
Posts: 85
Post Re: Missing spark
Yes, I did suspect the Boyer unit so I by-passed it but no change.
The unit itseld is very well sealed so I don't think that it's getting damp.


October 15th, 2020, 9:06 pm
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Joined: April 9th, 2010, 12:21 am
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Location: West Sussex
Post Re: Missing spark
I've never heard of a Boyer Bransden unit failing.


October 16th, 2020, 12:19 am
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Joined: March 21st, 2013, 12:04 am
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Location: Exeter, Devon
Post Re: Missing spark
The boyer doesn't stop the heal wearing and the points closing up. Clean and re gap your plugs.

Not sure if there is a fuse on ignition system, but clean the fuses and fuse holders. :)

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October 16th, 2020, 8:35 am
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Joined: March 21st, 2013, 12:04 am
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Post Re: Missing spark
Glad you posted, as I was having trouble getting a reasonable idle running on lpg
Took my own advice and closed up the spark plug gap. Much better now. :D

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October 16th, 2020, 3:32 pm
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Joined: October 22nd, 2014, 10:59 pm
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Post Re: Missing spark
The spark plug cables can get old and the water can go in. And dry isn't enough. They should also be clean as condense forms on dirt particles.


October 16th, 2020, 6:40 pm
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Joined: March 21st, 2013, 12:04 am
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Post Re: Missing spark
Valid point about ht leads as mine are getting a bit dire. Standard ones are a little to short as coil is mounted on gearbox. :)

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If you can't fix it with a hammer, it's probably electrical (or, an electric fuel pump!) ....


October 16th, 2020, 7:23 pm
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2CV Fan

Joined: December 27th, 2011, 9:50 pm
Posts: 85
Post Re: Missing spark
Funny how one thing leads to another!
Next damp day and no start, so much for cleaning connectors. Two hours leter and slightly warmer, and the car starts.
So I looked further. Checking the points I saw the contact tip was rattling in the arm. Never seen that before. New points and then checked static timing...no light at all on the tester no matter how far I moved the points casing. Ran a wire direct from battery, still no light. touched the test light earth on the engine, no light!
For some reason the battery earth to the gbox was not connecting properly. I moved the earth lead to the stud holding the air filter to the gbox and I had continuity. Bingo!

This explains, I think, why the starter was getting slower to turn and the engine seemed to fire when I released the starter on the key.Maybe because of the bad earth the starter was drawing all the power and not enough juice left for the coil.

Next cold/damp morning I shall know. These old bangers certainly keep the brain clacking away.

Thanks for your comments.


October 17th, 2020, 12:58 pm
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Joined: March 21st, 2013, 12:04 am
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Post Re: Missing spark
I tuned the key one Christmas morning, to hear a bang! The last few strands of ground cable had blown with the cranking amps. :o

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