Poor Ignition Coil Reliability (thoughts?)

[svenedin]

Time for you coil to move home, to maintain you original esthetic
Leave a coil mounted on dynamo with 2 dummy wires lost in loom with no connection and the king lead to distributor cap taped to real one. See how many notice 6 leads

Next time I'm with the car I'll look how it mounted and send you a picture.

Your point is well made. Originality is great but my car is a go anywhere car that gets used a lot. I can't have it breaking down due to coils failing. It's all very well when it breaks down on me because I can fix it very easily. It's another matter if somebody else is driving my car. Then it has really spoiled someone's day. A picture would be great. Many thanks Bill.

Stephen

[michael4]

So, from a reliability point of view, does the panel think that moving the coil to the inner wing is a GOOD THING?

Is it proven in any way?

[svenedin]

So, from a reliability point of view, does the panel think that moving the coil to the inner wing is a GOOD THING?

Is it proven in any way?

If you read old posts on this forum as I have been doing it seems that people have had multiple coils fail on the inner wing or the bulkhead as well. Some people say the coil gets cooled by the fan when it is mounted on the dynamo. It seems to be heated by the fan in my car with the hot air coming through the radiator. Quite the opposite effect. It is very difficult to draw any kind of evidence based conclusions as to where it is best to mount the coil.

I am definitely going to check the control box is properly limiting the charging voltage.

Stephen

[Bill_qaz]

Because of the doubtful quality of current coils you will definitely have less vibration body mounted than engine mounted, so diminishing one of the known failures.
But as always you will get multiple opinions( i just gave one) just decide what you want its your car.
You could mount a second coil on inner wing as we discussed and have wires ready fitted to plug in to existing .
A plug and play standby if you dynamo mounted coil fails

[myoldjalopy]

Because of the doubtful quality of current coils you will definitely have less vibration body mounted than engine mounted, so diminishing one of the known failures.
But as always you will get multiple opinions( i just gave one) just decide what you want its your car.

The interesting question is why did BMC decide to move the coil from the bulkhead to the dynamo during SII production (in spring 1955)? It remained there until the Minor ceased production entirely.
I do remember a 1966 traveller I once owned stopping suddenly on a motorway and when I opened the bonnet, found the dynamo mounted coil had somehow loosened and slipped (I can't remember how exactly now, decades years later!) and had shorted out on one of its terminals. I recall I was able to re-position/secure it quickly and get on my way again....
The coil in my current car (SII) is mounted at an angle on the bulkhead, so is not horizontal as it is when mounted on the dynamo, and I wonder if this makes any difference to potential faults - although Minors were not noted for coil failure back in the day.....the reported unreliability seems a modern problem.

[Bill_qaz]

I believe its more a quality issue than location. According to Google
Major Active Manufacturers
Bosch: Continues production of traditional cylindrical and blue classic coils via its dedicated classic division.
Standard Motor Products (SMP): Manufactures original-spec and high-performance classic replacement coils under lines like Standard Ignition and Blue Streak.
Lucas / Simon BBC (Viper range): Supplies oil-filled and modern oil-free dry canister coils built specifically for British and European vintage applications.
NGK / NTK: Maintains an extensive catalog of traditional canister and stock-setup ignition coils.
Bremi Fahrzeug-Elektrik: German manufacturer specializing heavily in ignition parts and classic electrical components.
Intermotor / Lucas / Valeo / Delphi: Regular OE and aftermarket suppliers that continue small-batch or continuous runs of legacy 6V and 12V ballast/non-ballast can coils

Unfortunately i believe the last four now have product made out of house, which often leads to quality issues and cost cutting

[svenedin]

The trouble is there are things we just don't know. For instance, what is the acceptable operating temperature of a coil and what is the upper limit? How hot is too hot, what is the temperature at which the coil is likely to fail? The manufacturer's would know this of course for their own products and so it might be possible to have a general idea of an acceptable temperature range.

On the bulkhead or inner wing there is relatively poor airflow for cooling but there is the heat sink effect of the bracket being bolted to the metal panel.

On the dynamo there is excellent airflow from the fan and from air rushing through the radiator when moving forwards. However, the air is pretty hot and so during a drive it may be that rather than cool the coil it is actually heated up! Of course if the coil continued to heat up it would eventually be cooled by the airflow. So if we assume an 82 C thermostat, the water in the radiator (at least near the top) is likely to be at least 82 C. The air going through the radiator will be heated up but the heat transfer will not be total so that air will be cooler than the radiator, at a guess about 50 or 60 C. Then the coil and the dynamo will heat up in the stream of hot air to reach a steady state which seems to be too hot to touch except briefly, maybe 50 or 60 C. These are estimates and I would have to use my infra-red thermometer to confirm. 60 C I would suggest is easily within tolerance, or should be, for a coil. When going faster the air will have much less time to transfer heat from the radiator and would be cooler. These estimates are assuming the car is stationary or travelling very slowly in traffic.

I will find my thermometer and do some measuring.

Stephen

[Bill_qaz]

On offside inner wing no exhaust heat quite a lot of air flow hole in bottom plate and shocker arm. Also yours and mine Stephen have cold air passing through the elephant trunk. Next time I use the car I'll take infrared temp gauge with me and take some coil temp reading on mine and let you know.

[svenedin]

Today I checked the voltage of the charging system to make sure no over-voltage was occurring. I measured the voltage between D and earth and raised the engine revs. The reading topped out at 14.6 volts, the battery being rather flat after multiple attempts to start it when the car broke down at the weekend (baseline battery voltage 11.9 volts; must charge battery). So the control box is working and the dynamo is not being allowed to overcharge which could be a reason for coils failing.

Whilst I was there and with the engine running and the car static on the drive I allowed the engine to get to steady state. Using my infrared thermometer I got the following readings:

82 C Top of radiator (82 C thermostat fitted)
71 C Bottom of radiator
53 C top of dynamo
48 C Coil

I also measured the dwell as an excessive dwell can cause the coil to overheat (the coil is in circuit for an excessive time). The dwell was 65 degrees which is exactly in-spec for Lumention Optronic electronic ignition. Incidentally, a fraction longer dwell than the upper limit of points ignition (57-63 degrees)

When I have been out for a run in the car and I remember to do it, I will repeat the measurements.

Another thing to consider with dynamo mounting is the presence or absence of the steady bracket 11G221. This cradles the coil at two points and reduces the tendency of the coil to wobble around. Perhaps BMC had issues with coils failing as a result of vibration. I don't know.

I have also meticulously been round the car checking earthing points. Making sure enough paint has been taken off for an excellent bare metal contact. I found no faults.

Stephen

[svenedin]

Just as an aside, when I was in the garage earlier I found a Lumention oil filled coil in a plastic box. This had been stored near the roof of my garage and had obviously got very hot during this hot summer. It has leaked quite a lot of its oil. Total mess. Tip: don't store oil filled coils where they will get hot!

To add to the list of coils that have a very good reputation for reliability, the Bosch "Blue" 9220081083 has an extremely good reputation. It is not easy to find and is expensive. It is an epoxy resin filled coil which is vibration resistant. I have bought one and it is my next coil to try.

https://www.boschautoparts.com/p/igniti ... 220081083-

Yes these are expensive but I have had 3 coils fail in 5 months! 3 different manufacturers. An oil filled "Remax" failed after 60 miles with open circuit primary coil. A replacement Pertronix 3 Ohm resin filled failed within 5 minutes whilst the car was still on the drive after I fitted it (this is very unusual for a Pertronix coil which are usually excellent). A Lumention oil filled died after about 600 miles (open circuit secondary windings).


Stephen

[geoberni]

Just as an aside, when I was in the garage earlier I found a Lumention oil filled coil in a plastic box. This had been near the roof of my garage and had obviously got very hot during this hot summer. It has leaked quite a lot of its oil. Total mess. Tip: don't store coils where they will get hot!

Stephen

I can't speak for the specifics of the Lumention Coil but generally in Coil construction, there is a screw holding the HT terminal receptacle in place. This is where oil is likely to leak from as the oil filled interior is directly below it..

[svenedin]

Just as an aside, when I was in the garage earlier I found a Lumention oil filled coil in a plastic box. This had been near the roof of my garage and had obviously got very hot during this hot summer. It has leaked quite a lot of its oil. Total mess. Tip: don't store coils where they will get hot!

Stephen

I can't speak for the specifics of the Lumention Coil but generally in Coil construction, there is a screw holding the HT terminal receptacle in place. This is where oil is likely to leak from as the oil filled interior is directly below it..

Yes that is exactly how that coil is constructed. It is exactly the same type of coil that failed causing my car to be embarrassingly conveyed back home from Warwick by the AA. The coil lasted 3 months on the car.......

Stephen

[Andmurph]

Just as an aside, when I was in the garage earlier I found a Lumention oil filled coil in a plastic box. This had been stored near the roof of my garage and had obviously got very hot during this hot summer. It has leaked quite a lot of its oil. Total mess. Tip: don't store oil filled coils where they will get hot!

To add to the list of coils that have a very good reputation for reliability, the Bosch "Blue" 9220081083 has an extremely good reputation. It is not easy to find and is expensive. It is an epoxy resin filled coil which is vibration resistant. I have bought one and it is my next coil to try.

https://www.boschautoparts.com/p/igniti ... 220081083-

Yes these are expensive but I have had 3 coils fail in 5 months! 3 different manufacturers. An oil filled "Remax" failed after 60 miles with open circuit primary coil. A replacement Pertronix 3 Ohm resin filled failed within 5 minutes whilst the car was still on the drive after I fitted it. A Lumention oil filled died after about 300 miles (open circuit secondary windings).


Stephen

We have a Bosch blue coil in the pickup that has been on there for 12 years according to the paperwork. The pickup was used as a commercial vehicle until 3 years ago, driving in woodland and on road. The coil is mounted above the alternator and never had any issues. The pickup came with a spare one in the trunk as well. Just in case.

[svenedin]

Just as an aside, when I was in the garage earlier I found a Lumention oil filled coil in a plastic box. This had been stored near the roof of my garage and had obviously got very hot during this hot summer. It has leaked quite a lot of its oil. Total mess. Tip: don't store oil filled coils where they will get hot!

To add to the list of coils that have a very good reputation for reliability, the Bosch "Blue" 9220081083 has an extremely good reputation. It is not easy to find and is expensive. It is an epoxy resin filled coil which is vibration resistant. I have bought one and it is my next coil to try.

https://www.boschautoparts.com/p/igniti ... 220081083-

Yes these are expensive but I have had 3 coils fail in 5 months! 3 different manufacturers. An oil filled "Remax" failed after 60 miles with open circuit primary coil. A replacement Pertronix 3 Ohm resin filled failed within 5 minutes whilst the car was still on the drive after I fitted it. A Lumention oil filled died after about 300 miles (open circuit secondary windings).


Stephen

We have a Bosch blue coil in the pickup that has been on there for 12 years according to the paperwork. The pickup was used as a commercial vehicle until 3 years ago, driving in woodland and on road. The coil is mounted above the alternator and never had any issues. The pickup came with a spare one in the trunk as well. Just in case.

That is exactly the kind of reliability I am looking for.

Stephen

[myoldjalopy]

I can vouch for the fact that the coil in my car has been operating faultlessly for over 40 years. The one I keep as a spare is over 70 years old!
I will wager that many good, old coils have been (wrongly) swapped out because of incorrectly diagnosed ignition problems and then left in situ. Or a new owner thinks "Oh, that coil looks old, I'd better replace it" In both cases, a mistake.
The theme here seems to be that (many) modern coils are of poor quality. The obvious answer to me is to hunt down an old one in working order.

[Bill_qaz]

Stephen, managed to grab a pic today. Its a Lucas coil and is bolted to the inner wing near the rebound stop bracket. Bit of a clean up and terminal fix on schedule now I've seen it for the first time since buying the car.

20260811_122731.jpg (643.12 KiB) Viewed 762 times

[svenedin]

Stephen, managed to grab a pic today. Its a Lucas coil and is bolted to the inner wing near the rebound stop bracket. Bit of a clean up and terminal fix on schedule now I've seen it for the first time since buying the car.
20260811_122731.jpg

Thank you. What you've got there is a good old coil of the type Myoldjalopy refers to. That's an old Lucas logo on the coil bracket. Yes clean up the terminals, give it a wipe and put it back! Whatever you do, don't join the Russian Roulette game of modern coils!!!

Stephen

[Bill_qaz]

Not even going to take it off, just going to reroute the black wire the other side of the HT lead and make sure the terminal is secure. The coating on the top looks like underseal
Will know better when heater duct is moved to give better access. The duct isn't bolted to the inner wing as it was retro fitted.

[svenedin]

Not even going to take it off, just going to reroute the black wire the other side of the HT lead and make sure the terminal is secure. The coating on the top looks like underseal
Will know better when heater duct is moved to give better access. The duct isn't bolted to the inner wing as it was retro fitted.

On the cars that had the duct fitted at the factory, it is held on the inner wing with brackets. These are still available but generally poor quality and prone to rapid rusting. There's a Mini supplier (Nippy Cars) that sells nice black powder coated brackets that don't rust. My car has those brackets.

Stephen

[svenedin]

I did one last tweak today. I checked all the spark plugs. They looked fine but I did two things. I have long favoured NGK BP6ES but I decided to try Bosch W7DC for a change so I changed all 4 for Bosch. I also reduced the spark plug gap to the standard 0.025" from 0.030". I have been running 30 thou for years since I started using high output coils but my theory is the standard 0.025" means less voltage is required to jump the gap and so all of the ignition system is less stressed. I drove 10 miles taking the dog to the vet and back and the car performed perfectly. There was absolutely no noticeable difference having changed the plug gap. Of note, the Bosch spark plugs were all perfectly gapped 0.025" straight out of the box. This never happens with NGK or Champion; I always have to adjust them. I am impressed with the Bosch plugs. There is a feel and look of very high quality about them (supplier Opie Oils). For Bosch plugs, lower numbers are cooler and higher numbers are hotter. W7DC is in the middle but depending on the engine you could go to cooler with a W6DC or hotter to a W8DC.

Stephen