Almost broke down!

[geoberni]

Even after a short run and stop, always attempt the restart without choke. The engine will retain heat for some time.

Really good to know, appreciate it

I think you may have had the Choke out too long and it was 'choking' on too rich a mixture.
My car even at the cooler temperatures we're experiencing at the moment, does not like much Choke after starting.
If I forget, she just doesn't fell as responsive.
I totally agree with mobylette, even an hour or two after stopping, Basil will happily start and run with no Choke.

[moggiethouable]

"her ignition was on a fair bit while he was checking power etc"

It's possible that this may have caused the coil to overheat, leading to partial failure.

Agreed. If one of the coil's internal wires has become JUST disconnected, any heating or vibration can result in your intermittent symptoms.

As an electrician, who's initial training included piston engine ignition systems (Distributors and Magnetos), I have to disagree with that.
Any break in the internals of the Coil will result in instant cut out of the engine, it is either generating a spark multiple times a second, or it is Dead as a Dodo.
I also had a Coil problem with my car when I first got him, which I reported on here some years ago.
Even if it were 'loose' making and breaking, the engine would be cutting out and then picking up again, it certainly wouldn't be drivable.

Any 'electrical' fault with the Coil will result in the engine cutting out or really rough running if the spark is intermittently not there when it should be.
Other faults such as high resistance connections on the Low Tension side can result in weak spark, but a Coil can't have the sort of effect you're implying.

But thanks for posting the comment, as I'm doing a talk on Vehicle Electrics at our Branch meeting next month. You've given me something else to cover.

for your talk, I was caught out by item 7, having checked the coil etc first.
An old unit makes and breaks with the engine vibrations.
You may have this covered already, in which case apologies.

[geoberni]

for your talk, I was caught out by item 7, having checked the coil etc first.
An old unit makes and breaks with the engine vibrations.
You may have this covered already, in which case apologies.

Another good point, thanks for the reminder. I'm still trying to find a balance between those that may understand absolutely nothing, and those that may be quite savvy on the subject.
We have our Feb meeting next week, so I'm going to see what sort of thing crops up.

[mrs.smith2012]

Thanks for the feedback everyone, the idea of it being the choke does make ALOT of sense so I’m thinking it’s that. Unfortunately the rain hasn’t stopped so haven’t had the opportunity to get her out for another run since then. Hopefully over the weekend

[mike1864]

"her ignition was on a fair bit while he was checking power etc"

It's possible that this may have caused the coil to overheat, leading to partial failure.

Agreed. If one of the coil's internal wires has become JUST disconnected, any heating or vibration can result in your intermittent symptoms.

As an electrician, who's initial training included piston engine ignition systems (Distributors and Magnetos), I have to disagree with that.
Any break in the internals of the Coil will result in instant cut out of the engine, it is either generating a spark multiple times a second, or it is Dead as a Dodo.
I also had a Coil problem with my car when I first got him, which I reported on here some years ago.
Even if it were 'loose' making and breaking, the engine would be cutting out and then picking up again, it certainly wouldn't be drivable.

Any 'electrical' fault with the Coil will result in the engine cutting out or really rough running if the spark is intermittently not there when it should be.
Other faults such as high resistance connections on the Low Tension side can result in weak spark, but a Coil can't have the sort of effect you're implying.

But thanks for posting the comment, as I'm doing a talk on Vehicle Electrics at our Branch meeting next month. You've given me something else to cover.

I was speaking from experience. A few years back my SII suffered similar symptoms to the OP's; momentary power losses. After 10 miles it gave up completely. I spent half an hour carrying out all the usual diagnostics, but failed to locate the fault. I didn't suspect the coil, as it was new (big mistake!). But then a final, desperate, cranking had it springing into life of its own accord, and we rushed on, just catching the Portsmouth ferry. It was fine for two years till we went on an MOT Le Drive, and it went intermittent again for a mile before conking out on the Duravel village roundabout. This time I DVM'ed the coil, whose primary was a solid infinite ohms. I replaced it with the original from the boot and it's been fine ever since.

The photo shows the 2mm break. But before I disturbed it by cutting the top off, it was probably a few microns; sometimes making, sometimes breaking, in response to the engine vibrations. I can't prove this was the same fault as two years earlier. But there's no other candidate.

Fifty years ago I had a similar encounter. For years the BBC's TV pictures from the Royal Albert Hall would suffer occasional breakup. But it was impossible to reproduce in tests, and hence remedy. Then one day I was round the back of a Broadcasting House equipment bay, and noticed that the inner of the incoming co-ax from the RAH was just resting on the terminal pin of its connector. They had never been soldered together from the day it was installed! No vibrations here (except the Victoria Line below!); so maybe just temperature variations &/or bright pictures.
I soldered it up, and it never went wrong again, till it all got replaced with fibre.
attachment=0]Broken coil.JPG[/attachment]

[geoberni]

I was speaking from experience. A few years back my SII suffered similar symptoms to the OP's; momentary power losses. After 10 miles it gave up completely. I spent half an hour carrying out all the usual diagnostics, but failed to locate the fault. I didn't suspect the coil, as it was new (big mistake!). But then a final, desperate, cranking had it springing into life of its own accord, and we rushed on, just catching the Portsmouth ferry. It was fine for two years till we went on an MOT Le Drive, and it went intermittent again for a mile before conking out on the Duravel village roundabout. This time I DVM'ed the coil, whose primary was a solid infinite ohms. I replaced it with the original from the boot and it's been fine ever since.

The photo shows the 2mm break. But before I disturbed it by cutting the top off, it was probably a few microns; sometimes making, sometimes breaking, in response to the engine vibrations. I can't prove this was the same fault as two years earlier. But there's no other candidate.

Interesting, but I really can't see a break like that causing your initial problem and then clearing up for 2 years ...
You'd be asking for the break in the coil to be making and closing almost as fast as the points were. I don't think a break of a few microns would remain stable with a combination of engine and road vibrations.
A break can really only get worse with the constant vibration, to me your case is in the Possible but not Probable category.
I too had a similar break in a Coil when I first got my car, After about 20 -40 minutes driving, it would cut out. The first time it happened it had fixed itself after Recovery home, most likely due to cooling down.
The 2nd occasion the fault was still there after Recovery and easily found with a Multimeter as you did. A year later I got around to opening the Coil and posted the findings here:
https://board.mmoc.org.uk/viewtopic.php ... 67#p636467

[mike1864]

I was speaking from experience. A few years back my SII suffered similar symptoms to the OP's; momentary power losses. After 10 miles it gave up completely. I spent half an hour carrying out all the usual diagnostics, but failed to locate the fault. I didn't suspect the coil, as it was new (big mistake!). But then a final, desperate, cranking had it springing into life of its own accord, and we rushed on, just catching the Portsmouth ferry. It was fine for two years till we went on an MOT Le Drive, and it went intermittent again for a mile before conking out on the Duravel village roundabout. This time I DVM'ed the coil, whose primary was a solid infinite ohms. I replaced it with the original from the boot and it's been fine ever since.

The photo shows the 2mm break. But before I disturbed it by cutting the top off, it was probably a few microns; sometimes making, sometimes breaking, in response to the engine vibrations. I can't prove this was the same fault as two years earlier. But there's no other candidate.

Interesting, but I really can't see a break like that causing your initial problem and then clearing up for 2 years ...
You'd be asking for the break in the coil to be making and closing almost as fast as the points were. I don't think a break of a few microns would remain stable with a combination of engine and road vibrations.
A break can really only get worse with the constant vibration, to me your case is in the Possible but not Probable category.
I too had a similar break in a Coil when I first got my car, After about 20 -40 minutes driving, it would cut out. The first time it happened it had fixed itself after Recovery home, most likely due to cooling down.
The 2nd occasion the fault was still there after Recovery and easily found with a Multimeter as you did. A year later I got around to opening the Coil and posted the findings here:
https://board.mmoc.org.uk/viewtopic.php ... 67#p636467

Prior to my second breakdown, the break was happily coming and going for several minutes, proving that this scenario - matching the OP's symptoms - does happen. Mine displayed several seconds of contact, then several seconds of open circuit; ie not related to the engine's rpm.
An intermittent connection's previous stabilising for a thousand miles seems unlikely (and very lucky). But it's the only diagnosis that fits my events.

Vibration, heat and the springiness/position of the wire all obviously play a part in such intermittent discontinuities. But here there's also arcing; this junction is carrying the same traffic as the contact breakers, but without the benefit of a spark suppression device. So a partial "remedial" weld is possible, albeit temporary, due to contamination with wire enamel, flux and cooling oil.

But we'll never know! Even a forensic, microscopic examination of the joint would have been scuppered as soon as the top was lifted off.
Hence my suggesting a hefty wallop to any suspect coil; and in several different planes. I reckon that such an extreme impact - outside the range of engine vibrations - is likely to permanently dislodge a dodgy contact, rather than repair it. And it wouldn't trouble a good joint.

But we all agree to carry a spare. And even if it's brand new, one of my branch members (yet another engineer!) sensibly recommends testing it in situ before putting in the boot.

[mrs.smith2012]

I meant to update on this! We managed to get under the bonnet on Sunday. Coil appears to be fine, although my friend did a bit of magic with the king lead as the connection was a bit iffy.
Plugs were absolutely black so they’ve been changed (I managed to do it under instruction - go me! ) and happy to report that she definitely feels much smoother and requires a lot less choke.
That said exhaust is still a little smoky and smelly so I suspect the carb might need a good clean up. It looked like it hadn’t been touched in a while. That will probably be the next job

[geoberni]

Prior to my second breakdown, the break was happily coming and going for several minutes, proving that this scenario - matching the OP's symptoms - does happen. Mine displayed several seconds of contact, then several seconds of open circuit; ie not related to the engine's rpm.
An intermittent connection's previous stabilising for a thousand miles seems unlikely (and very lucky). But it's the only diagnosis that fits my events.

Vibration, heat and the springiness/position of the wire all obviously play a part in such intermittent discontinuities. But here there's also arcing; this junction is carrying the same traffic as the contact breakers, but without the benefit of a spark suppression device. So a partial "remedial" weld is possible, albeit temporary, due to contamination with wire enamel, flux and cooling oil.

But we'll never know! Even a forensic, microscopic examination of the joint would have been scuppered as soon as the top was lifted off.
Hence my suggesting a hefty wallop to any suspect coil; and in several different planes. I reckon that such an extreme impact - outside the range of engine vibrations - is likely to permanently dislodge a dodgy contact, rather than repair it. And it wouldn't trouble a good joint.

But we all agree to carry a spare. And even if it's brand new, one of my branch members (yet another engineer!) sensibly recommends testing it in situ before putting in the boot.

Ahhh, some more details...
It's the 2 year gap that I find incredible, but perhaps you didn't do many miles in that time.

From your earlier comments, we've both clearly experience weird faults in the past, which influence our thinking.
The one lesson to take away from this discussion is that the old adage around these parts, of

It's never the Coil

is well and truly disproven, especially with anything produced in the last 40 years or so.


I've got quite a few strange and wonderful tales...
Like the aircraft which during start, would shut down the Auxiliary Power Unit (APU) if the Pilot contacted Air Traffic on the 'Local' frequency.
The Pilots lived with it for a while, just delaying contacting the Tower until after engine start.
But eventually we got to look at it.
We'd recently been given a new bit of test equipment which allowed us to monitor the APU Control Unit and it's various sensors on the APU, Temperature, Speed, amongst others.
Using this new bit of kit, we learned that the APU Control Unit was detecting an over-speed (or over-temp, I forget which) when the call to the Tower was made.
Cutting a long and tedious story short, we found that the Radio guys had replaced this aircraft's upper VHF Aerial and it's cable some months before.
In fitting the new cable, they had not routed it exactly how the old one was fitted and had cable tied it, only for about 9" or so, right next to the cable loom carrying the APU wiring. The electromagnetic interference radiated by the aerial cable was inducing a signal into the APU sensor wiring which made the Control Unit think there was an APU fault.
Got the Radio guys to do their job properly, and follow the designated clipping points and snag fixed.
The problem had only arisen when the Tower had changed some of it's local radio frequencies; something which was done periodically just to make the Soviets do some work when eavesdropping. This was in the '70s before secure radios became standard.

[XWL61]

Whilst we are talking faulty coils..... I replaced my coil at Xmas - it came with an Accuspark electronic distributor I bought a few years back. I decided to fit the distributor having re-discovered it in the garage. However I didnt have suitable sized replacement vacuum pipe so abandoned the idea. I did however fit the coil. All well for a couple of weeks, then one wet morning the car wouldn't start. Eventually coaxed it into life. All was well until a few days later - a similar problem. Again coaxed it into life, but on my journey there was clearly something wrong. The car finally died. Whilst poking around under the bonnet in the fading light, I noticed a spark tracking from the +ve coil terminal to the king lead when the engine was turning over on the starter. Re-fitted the old coil - no problems since. Any thoughts from our electrical wizards??

Andy

[mike1864]

I would have thought that such "tracking" would only happen if the path was unusually conductive, due to moisture, dirt or a wayward strand of wire.
Alternatively, do you have a meter to measure the ohms between these three terminals on the suspect coil?

[geoberni]

Whilst poking around under the bonnet in the fading light, I noticed a spark tracking from the +ve coil terminal to the king lead when the engine was turning over on the starter. Re-fitted the old coil - no problems since. Any thoughts from our electrical wizards??

Andy

Is the Car Pos Earth?

Where was the spark exactly?
Was it jumping from the base of the King Lead to the Pos Terminal; that's one heck of a gap??
A surface crack in the top insulator from the sounds of it.
But the energy built up in a Coil is going to jump the smallest gap it can find. That's why a faulty Dissy Cap can allow the Spark to bleed off along a crack rather than go via the Plugs.
It seems strange to jump where you saw it, rather than at the Spark plugs

Coil Top.JPG (9.5 KiB) Viewed 36491 times

[myoldjalopy]

I meant to update on this! We managed to get under the bonnet on Sunday. Coil appears to be fine, although my friend did a bit of magic with the king lead as the connection was a bit iffy.
Plugs were absolutely black so they’ve been changed (I managed to do it under instruction - go me! ) and happy to report that she definitely feels much smoother and requires a lot less choke.
That said exhaust is still a little smoky and smelly so I suspect the carb might need a good clean up. It looked like it hadn’t been touched in a while. That will probably be the next job

Black plugs may mean over-use of the choke in the first place, but it might have been running a bit rich. Won't do any harm to clean the carb dashpot and piston and check the mixture for good measure. Good that the car feels smoother - now go back and see if that sheep is OK!

[mrs.smith2012]

I meant to update on this! We managed to get under the bonnet on Sunday. Coil appears to be fine, although my friend did a bit of magic with the king lead as the connection was a bit iffy.
Plugs were absolutely black so they’ve been changed (I managed to do it under instruction - go me! ) and happy to report that she definitely feels much smoother and requires a lot less choke.
That said exhaust is still a little smoky and smelly so I suspect the carb might need a good clean up. It looked like it hadn’t been touched in a while. That will probably be the next job

Black plugs may mean over-use of the choke in the first place, but it might have been running a bit rich. Won't do any harm to clean the carb dashpot and piston and check the mixture for good measure. Good that the car feels smoother - now go back and see if that sheep is OK!

I think it was a combo of both, dash pot and piston could definitely do with a bit of TLC so will get onto that. She certainly feels better. No sign of sheep so assuming he ran away