Its never the Coil

[mike.perry]

It was the B'@@@@y coil that packed up on me on Wednesday night. Engine suddenly expired with no life in the ignition circuit on the Traveller. Tested the coil on the Series MM still nothing. Dug out a spare coil, tested it on the MM - perfect. Fitted it to the Traveller and back in action.
The problem was that as we have been informed that it is never the coil I was not carrying a spare and it took 3 1/2 hours for recovery to arrive. I think that I will fit a spare on the bulkhead as I have on the Series MM

[lambrettalad]

oh dear

[bmcecosse]

Nahhhh - you're pulling my leg!!
So - what make? A good old coil, or a nasty modern repro?? I you put a meter on it -what ohms does it read now??

You do know that when I say it's 'never' the coil - just sometimes it IS.....just not nearly as often as everybody thinks!!!

[dalebrignall]

i allways carry a spare,touch wood never needed it .the day i dont have it is the day it fails .

[brucek]

The only occasion when I can categorically state - it was the coil - was on the way back from MOT 89 - half way through France. Just as I was thinking things were going very well, there was a dull thud, and an instant loss of power plus the smell of oil burning. Thinking I had thrown a rod or something I free-wheeled onto the hard shoulder, opened the bonnet and saw the contents of the coil distibuted liberally and without favour all around the engine bay.

After gathering up yards of thin red wire, and detaching it from all the various parts etc. I walked to the local gendarmerie which was helpfully about 500 yards from where the car was. Trying to explain - it's my coil - in French that sounded more like Crabtree from 'Allo 'Allo - the gendarme phoned a friend and before we knew it the said friend appeared with his flatbed truck and whisked me off to his garage (Citroen) whereupon he rumaged in his parts department and found and fitted a new coil. He wouldn't take any payment either. Off we went into the remaining sunset - I left the coil on until I took the old girl off the road in 1990!

Oh by the way, it was during this trip that I realised that you dont fit Intermotor ballast resist coils to 948 Minors!!! - still, I was only young

[bmcecosse]

Yes - if you fit a 2 ohm coil and run it on 14 volts - it WILL be the coil!! You were lucky it lasted as long as it did....

[JOWETTJAVELIN]

So what is the purpose and benefits of a ballasted coil?

[brucek]

It coats your engine bay in rust proofing oil when it explodes????? search me - still don't know - 23 years later I'm sure Roy will explain it all shortly

[lambrettalad]

I understand it takes a lower voltage to start the car ( both memory cells need charging )

[bmcecosse]

It runs at 9 volts.......so during normal running it is fed through a ballast resistor (of about 1 to 1.5 ohms) which limits the volts seen at the coil to 9 volts. But during starting - when the battery volts are dragged down to ~ 9 or 10 volts, it is fed directly from the battery (via a relay operating in tandem with the starter) so it gives full value sparks to the plugs - and not the weakened sparks a normal system provides when a 14 volt coil is forced to struggle through with only 9 or 10 volts during starting. Simples !

[brucek]

There you go - you learn something every day Thanks Roy

[JOWETTJAVELIN]

Thanks

[lambrettalad]

Ta Roy (both brain cell now re-charged)

[hanvyj]

I think, being the case with most parts - if its new then chances are its probably going to break soon...

If its an origional coil it will probably just keep going forever - if its a modern one never rule it out! Contact corrosion is a common problem though and that might make you think your origional coil is dead

[autolycus]

It runs at 9 volts.......so during normal running it is fed through a ballast resistor (of about 1 to 1.5 ohms) which limits the volts seen at the coil to 9 volts. But during starting - when the battery volts are dragged down to ~ 9 or 10 volts, it is fed directly from the battery (via a relay operating in tandem with the starter) so it gives full value sparks to the plugs - and not the weakened sparks a normal system provides when a 14 volt coil is forced to struggle through with only 9 or 10 volts during starting. Simples !

To save folk looking for a relay that may not exist, a common approach is to feed the coil via either an external ballast resistor, or via a length of resistance wire built into the loom (pink, iirc, bicbw). The bypass when the starter is operated is then simply an extra, normal, wire from a terminal on the starter solenoid to the coil. So still, technically, via a relay, but a relay that's part of the solenoid not a separate item.

If an engine starts, but then dies as soon as you release the ignition switch to its normal position, chances are that the ballast resistor or resistive cable have burned out.

Kevin

[bmcecosse]

Yes - but it has to be a special solenoid with the additional contacts built in - you can't just use the standard solenoid...... Or it can be part of the pre-engaged starter system. Anyone wishing to convert their Minor would be best to just use a separate relay.