how many bubbles?

[geoberni]

Every day is a school day.
I vaguely remember some years ago buying a set of silicone leads that arked (?) from new. I could see them arking if I lifted the bonnet in the dark. They were expensive too, with 'bendable' ends. Took them back for a refund.

It's 'arced'
Back in the day you used to get suppressor end caps with resistors in them, these days the carbon (or otherwise) cored cables have a built in resistance per mtr of about 5K - 10K Ohms.

It's not a problem with modern engines because the Spark generation is done very near the plugs.
I think the build quality of early Silicone leads could sometimes result in the Electrical pulse escaping through the insulation. I've had a gentle tingle from an HT lead before now, when it should be insulated enough to not feel anything.

[stuffedpike20]

Thanks berni.
'Arced' sounded a bit rude.
Ran the car on the drive yesterday, but did not go for a drive because I did not want to konk out in the rain. It seems fine, but time will tell...

[Myrtles Man]

https://en.wikipedia.org/wiki/Electric_arc

https://www.yourdictionary.com/ark

[stuffedpike20]

Just been for a test drive.
Ran well until the engine warmed up, then started missing like mad. Even got some backfires.
Limped home getting some funny looks at kangarooing car.

Now I suspect the condenser. will change for an old one this afternoon.
I think I have had this problem before with a condenser. Engine ran fine until warmed up.
What fails with a condenser, and makes it give a 'splashy' spark?
I have read on the DD website it is not enough windings?

[oliver90owner]

It is more likely the coil than the condenser. What colour was the spark when the problem arose?

[myoldjalopy]

To reply to the question about condensors, the Good Doctor says not enough windings. He also says that in poor quality ones, "the internal bonding & construction also left a lot to be desired."
So basically poor quality materials and poorly made.

[geoberni]

The only 'Windings' are in the Coil.
A Condenser is actually a Capacitor. It's an electrical gap.
It's there to reduce the spark at the contact points as they open in the distributor and minimise burning and pitting of the points. Arcing is caused by the effect of self induction in the coil as the points interrupt the flow of current.


If the Capacitor/Condenser is breaking down when warm, it weakens the strength of the spark getting to the plugs.
If the points arc, then they will drain the energy that was intended for the spark plug.
The capacitor momentarily keeps the primary current flowing so the voltage across the points is below the point's arcing voltage, until the gap has opened up a bit more.
it's all over in a few milliseconds, but that's the gist of it.

I did a quick internet search to get a diagram and the first one I found was incorrect! This Condenser is incorrectly wired up!
It's supposed to be in parallel to the Points; it's actually bypassed by the straight line connection to earth that I've indicated, plus it's on the wrong side of the points.!!!! So much for 'The Classic Mechanic 2011'....

Ignition P C.jpg (97.07 KiB) Viewed 1455 times

For a simple and short video of the way it actually works, see this link: https://www.youtube.com/watch?v=lWyn_eV-DzM

[geoberni]

To reply to the question about condensors, the Good Doctor says not enough windings. He also says that in poor quality ones, "the internal bonding & construction also left a lot to be desired."
So basically poor quality materials and poorly made.

The use of the term 'Windings' is a little misleading.

Windings is the term used for the wire in a transformer or in the case of our cars, the Primary and Secondary windings of the Coil.

A Condenser, or capacitor of the type used in an ignition system is a 'Film' or 'Paper' Capacitor, where the 2 plates of the device are rolled or 'wound' around each other simply to fit them into as small a space as they can.

So IMHO, if the DD is finding Condensers with insufficient 'windings' what they are actually finding is a capacitor that isn't of the value it's supposed to be i.e. the 'plates' are too small an area.
A video I found here of a guy cutting one open, showing the foil and the insulating film.: https://www.youtube.com/watch?v=B6XepxH ... e=emb_logo

[oliver90owner]

I note that the ballast resistor is shown wrongly wired, too. If M stands for motor, there woulld be a huge current through that coil (or more honestly virtually nothing through the starter motor (assuming the points were closed when initiating a start). Condensers are not polarity conscious, either. Not bothered to document any other ‘bloomers’. Can’t trust all you see and read on t’internet.

[stuffedpike20]

It is more likely the coil than the condenser. What colour was the spark when the problem arose?

Tried 2 different condensers, and a replacement coil.
No change.
Confused now !

[geoberni]

It is more likely the coil than the condenser. What colour was the spark when the problem arose?

Tried 2 different condensers, and a replacement coil.
No change.
Confused now !

Were they new or old ones of suspect heritage? the number of people who have old bits they should have thrown away because they were changed for a reason originally is quite high. Been guilty myself sometimes.

No change on a test drive or just while running with your head under the bonnet?
Does it sound like it's missing a spark or two here and there?

[oliver90owner]

Confused now

Or still confused?

Could yet just be a faulty ignition switch. Do you hang a huge bunch of keys, or heavy fob, on it, along with the ignition key? It would not be the first time....

[stuffedpike20]

Missing several sparks I think. Head under the bonnet, too lumpy to drive.
The condensers were old but good when replaced, as is the replacement coil.
Going to check the timing again tomorrow.

Rotor arm is fairly new red one from Dis Doc.
Plugs are new champion N9YC
Points are new old stock Lucas, with 'Lucas' stamped on them.
Dissy cap in good condition.
No vacuum in tank.
New petrol.
Coil is Lucas sport.
Float valve is recent.

Problem seems to start when engine warms up.

[oliver90owner]

Have a look under the bonnet, with the engine running, in the dark. A good check to see if sparks are going somewhere they should not be.

[stuffedpike20]

Will do oliver.
I think I will have to do a compression test too, to rule out head gasket problem.
Does backfiring mean it is more likely to be an ignition problem, rather than a fuel problem?

Thanks, John.

[stuffedpike20]

I spent a couple of hours this afternoon changing condensers, points, coils, distributor caps and leads.
Set the static timing and points gaps a couple of times, and now the car seems to be running OK. No Idea what has gone right.

Thanks for all suggestions.
John.

[myoldjalopy]

Well, the only way to have found out would be to have changed each thing one at a time and testing in between. You could, I suppose, undo what you've done, one at a time, until it goes wrong again just to find out, but I wouldn't bother - and I doubt you will want to either!
Great news it seems all OK now - fingers crossed for happy, trouble-free motoring.

[stuffedpike20]

Thanks myold.
Not road tested it yet, so might be back............