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Post by dave1800 on Nov 20, 2012 11:06:52 GMT
Kels Sorry I missed this possible vital clue earlier. The only way your spark tester could show a spark with the rotor arm missing is if it tracked between the carbon brush in the distributor cap and the plug lead terminal inside the cap . Once you have this type of tracking the cap is useless. Whether the track existed before you tried the engine with no rotor arm in place is almost impossible to determine, but I'm afraid you need another new distributor cap. If it was tracking earlier then this would weaken or extinguish the spark and prevent starting. Now why it happened after a run and leaving it standing  ?? Regards David Cleaned old points set the gap and fitted new condensor, tried starter under the bonnet and got weak reading at the HT tester. I then noticed the rotor arm sitting on the side of the radiator. How the spark tester was indicating a spark is beyond me. Fitted the rotor arm and still got a weak looking spark. Regards Kels |
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Post by kelsham on Jan 27, 2013 14:44:03 GMT
Thought i had better report on my own thread, thanks for the sympathy, I am slowly
recovering.
Went out today and checked for a spark using one of the testers that go inline with the plug lead. It showed a flashing light.
I have come to mistrust this tool because of previous results. I substituted a flash tester and there was no spark across it.
A check using the King lead also looked very poor.
After some thought,several cups of tea, with a final shot of brandy and urging from the wife who thinks I am idle, with some justification, I returned and substituted the coil with a coil I have not tried before. It was pretty disreputable looking. After a clean of the connection points and further checks round the wiring which proved a waste of time I turned the key and she immediately fired up.
It looks as if the coil was faulty. As I replaced it recently I may have brought this on myself.
I removed the pile of rotor arms from the front panel and went for a short drive, success for the time being. I looked at the no's on the coils and also the connector markings. Does anyone know what a positive earth coil no is?
Regards Kels.
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Post by tommydp on Jan 27, 2013 17:46:53 GMT
Hi! I believe if the therminals are marked CB and SW it's a positive earth coil. They are also stamped with year at the back, for example 70 for 1970.
I would imagine all coils before '72 or so are positive earth. I have a coil from '70 among my piles of spares, which has + and - marked therminals, so obviously they quit the SW and CB letters before they switched from positive to negative earth. Its number is 45208A. And it's called HA 12. I'll have other coils somewhere, so I'll have a look for other numbers later.
Tommy
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Post by kelsham on Jan 28, 2013 7:20:32 GMT
I get a feeling of having been here before. I must be close on Tommys heels as regarding parts fitted, removed replaced, refitted in chasing poor starting. Or in his case poor running.
I am completley fuzzy as to what I have actually done over the last 2 years.
I will leave it for a couple of days and try a cold start.
I have a write up somewhere on how to test a coil for polarity, I will try to find it and check the coils I have.
I am not sure that the sw/cb are a reliable indication of polarity. I am sure I had a negative earth coil with these markings on my BSA Trike.
Regards Kels.
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Post by dave1800 on Jan 28, 2013 9:28:22 GMT
Kels Scroll about 3/4 down the page. mgaguru.com/mgtech/ignition/ig104.htmIf you get it wrong it reduces the spark by around 15% - 30%. Just ignore the description as to how the coil produces its HT; it actually relies on the speed at which the primary current is switched off to induce a back EMF of up to 400V in the primary windings which is then stepped up by the transformer design. As transistors switch faster than a contact breaker you can achieve a higher voltage with the same coil. Many Fords ran double ended coils in the 1980s-90s with one end +ve and the other negative which runs contrary to good practice - but they were high power consuming about 6 amps so had more in reserve. The Fords still ran OK, but better to get it right for the Lucas coils used on the B series especially when it's cold. Regards David [quote author=kelsham board=tech thread=360 post=3300 time=1359357632 I have a write up somewhere on how to test a coil for polarity, I will try to find it and check the coils I have. I am not sure that the sw/cb are a reliable indication of polarity. I am sure I had a negative earth coil with these markings on my BSA Trike. Regards Kels.[/quote] |
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Post by kelsham on Jan 29, 2013 8:35:11 GMT
Thanks, a good write up, I will use a meter to check the polarity.The method is much simpler than the method I used last time. As I recall it involved taking readings with the coil disconnected.
I knew about the pencil method, but cant persuade Yvonne to hold the pencil while I crank the car? Thats women for you.
Regards Kels.
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Post by kelsham on Feb 7, 2013 13:33:38 GMT
I went to the garage today, turned the key and after turning over a few times she fired up. I stopped the engine and restarted immediately.
Looks good as soon as the salt dies down I will go for a run.
Regards kels.
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Post by indianajones on Feb 7, 2013 19:27:12 GMT
Been quietly reading this thread in the background as I don't know too much on the subject, but has made good reading  Glad to see you've got it sorted it. As for women helping, my wife doesn't mind giving me a hand from time to time, but doubt she would if it involved getting oily lol -Andrew |
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Post by kelsham on Feb 8, 2013 8:42:35 GMT
Yvonne is usually very good about helping, she realised that holding a carbon pencil in the H.T. system could get interesting.
As she said ' I didn't marry you for excitement'.
Seriously, I was beginning to think I would never resolve the problem.
It goes to show too many changes just cause confusion. I am staying with the points having read the thread on substitute ignition systems.
Regards Kels.
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