Poor Ignition Coil Reliability (thoughts?)

[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.

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

Yes I bought a pair but with all the stuff on inner wing I'd have to move bits so just used 1 cable tied to bonnet pull to stop the pipe flopping.

20250213_151437 (1).jpg (764.1 KiB) Viewed 384 times

[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

Yes I bought a pair but with all the stuff on inner wing I'd have to move bits so just used 1 cable tied to bonnet pull to stop the pipe flopping.
20250213_151437 (1).jpg

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen

[svenedin]

Looking at the workshop manual AKD530 the coil specified for the 1098cc is Lucas LA12 with a primary resistance of between 3.2 and 3.4 Ohms.

All of the internally ballasted coils on sale these days seem to be 3 Ohm with the exception of the Bosch Blue 922081083 which is quoted as 3.4 Ohms. Whether this small difference in resistance has any bearing at all on failure rates I don't know but it seems unlikely. At 12 volts an increase in resistance of 0.4 Ohms decreases the current flowing through the coil from 4.0 amps to 3.53 amps as compared to a 3.0 Ohm coil.

The voltage required to jump a 0.025" spark plug gap is around 8,000 volts at the pressure in the cylinder and with the presence of fuel. The voltage required is a lot less in room air. "Sports" or high output coils claim very high output voltages e.g 40,000 volts but at the standard plug gap they reach nothing like that voltage. These high output coils have very many more secondary windings (because they are similar to a step-up transformer) and so I wonder whether they are a lot more fragile as a result. Only reliable failure data (which we do not have) would answer this.

Stephen

[michael4]

Not long ago I removed the 'Spitfire Multispark' from the coil to distributor lead.

Guess what...no discernible difference.

I am inclined to open it up and see what is in inside.

[svenedin]

Not long ago I removed the 'Spitfire Multispark' from the coil to distributor lead.

Guess what...no discernible difference.

I am inclined to open it up and see what is in inside.

According to this https://www.nortonownersclub.org/forum/ ... spark-unit it consists of two ferrite washers and a gap. Sounds like Snake Oil like so many ignition related products!

Stephenn

[Bill_qaz]

[/quote]

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen
[/quote]
I believe when the fresh air intake type heater was introduced the DB10 unit for flasher was no longer used, so more space available on inner wing.
Your horn being on offside, is that the position for second horn when hi and low tone used? Or at some point was the single moved from nearside to offside? Mine is definitely OE wiring to nearside front position.

[svenedin]

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen
[/quote]
I believe when the fresh air intake type heater was introduced the DB10 unit for flasher was no longer used, so more space available on inner wing.
Your horn being on offside, is that the position for second horn when hi and low tone used? Or at some point was the single moved from nearside to offside? Mine is definitely OE wiring to nearside front position.
[/quote]

I think for late cars like mine, offside (for RHD) is the normal position for a single horn. Certainly when I fitted the new wiring loom that was where the horn wires lined up. It could not be on the nearside without wiring modification. I must have a look and see if there are any mounting holes on the nearside. I don't think so.

Stephen

[MikeNash]

Svenedin asks for “thoughts or experiences”, so may I recommend a brand of coil? I think he should consider the Runbaken oil filled coil that was popular in the 1940s and 50s, and that’s shown and discussed on the Austin 7 site here https://austinsevenfriends.co.uk/forum/ ... p?tid=7364
Launched in 1941 it was some two to three times the cost of the current Lucas coil, and it came with a two year guarantee. (Which I suspect that was very unusual for the time.) It also had a cast alloy holder with a unique serial number, all of which suggests to me that it was a well-made product with careful quality control. There’re still many around on ebay, etc and that they’ve lasted is itself a recommendation. Finally, because the coil is contained in a glass bottle, Svenedin can eyeball the innards to assure himself it’s still all stuck together properly.
I’ve a 6 volt example with what looks like a period ballast resistor, a block of carbony material ¾ inch in diameter and ¼ inch thick. With 13 volts applied to the primary the coil gives an output of 32kV and with the ballast resistor in circuit it gives 21kV. I like period aftermarket bits and so I recommend to you all the Runbaken coil; fit one, it’ll brighten up your engine bay!
The only “downside” is that the oil may be PCB (polychlorinated biphenyl) which is dangerous, so if you break it (unlikely, it’s very tough) don’t touch the stuff or sniff or drink it. MikeN.

[svenedin]

Svenedin asks for “thoughts or experiences”, so may I recommend a brand of coil? I think he should consider the Runbaken oil filled coil that was popular in the 1940s and 50s, and that’s shown and discussed on the Austin 7 site here https://austinsevenfriends.co.uk/forum/ ... p?tid=7364
Launched in 1941 it was some two to three times the cost of the current Lucas coil, and it came with a two year guarantee. (Which I suspect that was very unusual for the time.) It also had a cast alloy holder with a unique serial number, all of which suggests to me that it was a well-made product with careful quality control. There’re still many around on ebay, etc and that they’ve lasted is itself a recommendation. Finally, because the coil is contained in a glass bottle, Svenedin can eyeball the innards to assure himself it’s still all stuck together properly.
I’ve a 6 volt example with what looks like a period ballast resistor, a block of carbony material ¾ inch in diameter and ¼ inch thick. With 13 volts applied to the primary the coil gives an output of 32kV and with the ballast resistor in circuit it gives 21kV. I like period aftermarket bits and so I recommend to you all the Runbaken coil; fit one, it’ll brighten up your engine bay!
The only “downside” is that the oil may be PCB (polychlorinated biphenyl) which is dangerous, so if you break it (unlikely, it’s very tough) don’t touch the stuff or sniff or drink it. MikeN.

Thank you Mike,

I do wonder whether it is the PCBs that made old oil filled coils nearly immortal !

It's amazing how long old electrical equipment lasts for. I have an electric doorbell that was made in the late 1890's. It has platinum contact breakers and it is still going strong. Beat that modern rubbish!

Stephen