Discussion
Today my Daimler SP250 came to an embarrassing halt halfway up a large bridge. It turned over, and struggle to fire but that was all. I had it towed home where I got it idling but it would die when revved. I noticed out the corner of my eye that the coil plug lead was arcing to the coil positive terminal. I removed the coil (Pertronix/Ignitor Flamethrower) and found a hairline crank where the rubber insulation boot slips on. That was where it was arcing. The coil is about 6 years old. I wrapped the end of the coil with insulation tape and the car ran properly. I've ordered a new coil, but wondered if anyone might know what caused the crack in the first place?
I had this same problem a few years ago.
The coil fitted to my car had a date stamp in the fifties and I thought it prudent to fit a new coil as part of a general service. Bought one from a well known MG parts supplier and duly fitted. Just a couple of weeks later my car ground to a halt for the first time and on closer inspection I saw the coil arcing across the same place as yours. There was no damage, still looked brand new. Phoned home (luckily only a few miles away) and wifey brought out the old coil from the shelf in the garage. Fitted on the road side and away we went. Asked around a few other classic owners and was told crap quality parts from china. Still running the old coil and now look out for original NOS parts or use the distributor doctor.
Jon
The coil fitted to my car had a date stamp in the fifties and I thought it prudent to fit a new coil as part of a general service. Bought one from a well known MG parts supplier and duly fitted. Just a couple of weeks later my car ground to a halt for the first time and on closer inspection I saw the coil arcing across the same place as yours. There was no damage, still looked brand new. Phoned home (luckily only a few miles away) and wifey brought out the old coil from the shelf in the garage. Fitted on the road side and away we went. Asked around a few other classic owners and was told crap quality parts from china. Still running the old coil and now look out for original NOS parts or use the distributor doctor.
Jon
Apart from saying the word is tracking, not arcing, I will say that if ignition coils are treated well they do not deteriorate, so if it works do not replace it.
The one way of knackering a coil that does work well is to leave the ignition on when the engine is not running - e.g. to listen to the radio in a car like the SP250 that pre-dates modern ignition switch logic. Szodt's Law says that if you do that the points will be closed and consequently current will flow continuously through the coil's primary which will overheat. That can result in coil-based intermittant ignition problems.
The one way of knackering a coil that does work well is to leave the ignition on when the engine is not running - e.g. to listen to the radio in a car like the SP250 that pre-dates modern ignition switch logic. Szodt's Law says that if you do that the points will be closed and consequently current will flow continuously through the coil's primary which will overheat. That can result in coil-based intermittant ignition problems.
What many people fail to realise is that the 'rules' of electricity work whether the item (in this case a coil) is a standard or high output unit. The 'spark' simply looks for the easiest flow route - in your case it was to earth due to the damage. Use of a higher powered coil will mean that it will just take that same route - but now just that much easier!
roscobbc said:
What many people fail to realise is that the 'rules' of electricity work whether the item (in this case a coil) is a standard or high output unit. The 'spark' simply looks for the easiest flow route - in your case it was to earth due to the damage. Use of a higher powered coil will mean that it will just take that same route - but now it will flow that much easier!
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