Lotus Elan

Ignition coil failures - is it just me?

PostPost by: AHM » Mon Apr 17, 2017 8:15 pm

Is the coil body earthed?

When was the last time you changed the Main HT lead?
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PostPost by: nigelrbfurness » Fri Apr 21, 2017 7:46 am

The coil body is earthed - I think someone else asked that too. I used to use silicone leads and found they needed replacement every couple of years or so, so recently switched back to copper core making my own from stock bought I think from AES or possibly Holden. I suppose they could be the problem?
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PostPost by: UAB807F » Fri Apr 21, 2017 4:10 pm

nigelrbfurness wrote:The coil body is earthed - I think someone else asked that too. I used to use silicone leads and found they needed replacement every couple of years or so, so recently switched back to copper core making my own from stock bought I think from AES or possibly Holden. I suppose they could be the problem?

Unlikely I would have thought Nigel, apart from a brief trial of some silicone leads I'm also on copper core leads with NGK suppressors, again home-made. I only recently replaced the Bosch coil which has been there for, well, 20+ years I'd guess, and that was because it was looking scruffy rather than not working ! (it's in the boot, just in case... )

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PostPost by: davidholroyd » Mon Sep 04, 2017 9:06 pm

The HSCC made me go back to an old coil and points for a while for racing. No matter what I tried all the 'modern' bits for points, coil etc were rubbish. Not a patch on what was made 20 / 30 years ago.

My advice is modern electronic ignition ...

www.h-h-ignitionsolutions.co.uk/perfdist.htm
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PostPost by: rgh0 » Tue Sep 05, 2017 11:34 am

davidholroyd wrote:The HSCC made me go back to an old coil and points for a while for racing. No matter what I tried all the 'modern' bits for points, coil etc were rubbish. Not a patch on what was made 20 / 30 years ago.

My advice is modern electronic ignition ...

http://www.h-h-ignitionsolutions.co.uk/perfdist.htm


Bosch coil, Magnecor leads, NGK plugs, Bosch dizzy components in a billet body with roller bearings and with 911S points works for me up to 9000+rpm. The Bosch 911S points are NLA but I have bought all the spares in the world off Ebay so i have a lifetime stock :). An identical points set with a lighter spring is still made and I can always modify these with a heavier spring if I run short. Unfortunately the guy who made my two special dizzys has retired:(

In my racing class you can only use electronic ignition if its inside the dizzy and these seems to struggle in racing situations due to over heating

cheers
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PostPost by: RichC » Tue Sep 05, 2017 5:36 pm

keep going & you'll get there in the end.
I too got thru a lot of coils for a while with varying reasons why they weren't lasting most of which have been covered already in this thread :lol: having a +ve earth didn't help my situation initially ....but it's all solved and i've since moved on to electronic ignition which initially caused a few hiccups as i unknowingly had a ballasted system .
All sorted now .
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PostPost by: peteleo » Thu Sep 07, 2017 2:41 am

I believe the coil body should not be earthed. All coils with metal housings can be tested for grounded wires to the casing by touching each terminal to the casing. A coil is an electromagnetic device it would defeat the purpose of operation if the primary or secondary winding were grounded to the casing ??
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PostPost by: wotsisname » Thu Sep 07, 2017 7:52 am

The workshop manual (+2) clearly shows a ground strap (braided) from coil mounting bracket to the oil pump. Possibly to ground one of the coil windings or discharge magnetic field [my knowledge of electronics is a pretty sketchy !]
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PostPost by: bob_rich » Thu Sep 07, 2017 8:49 am

Hi All

I agree it is good practice to earth the body of ignition coils with metallic cases. The service manual recommends this for minimising ignition interference to the radio. The reason is that when the spark plug breaks down under the rising voltage ( rising in magnitude irrespective of polarity) this breakdown is a very fast effect typically less that 1 millionth of a second ( <1microsecond ). At the point of breakdown the stray capacitance of the coil innards to the case will be discharged and by providing a good grounding to the engine block this resultant short current pulse will find a direct path and not flow through the wiring of the car. this current will always find its way to earth and may develop short high voltage pulses in places where the voltage insulation of the wiring ( or the coil innards) is not rated for such voltages.

This could be more important now some cars have after market electronic ignition system or engine management systems that could be miss triggered by the uncontrolled flow of current around the car wiring.

Bob
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PostPost by: peteleo » Thu Sep 07, 2017 2:17 pm

Thanks, i understand now why the coil should be grounded to minimize radio interference. Also, i'm referring to checking a coil for shorts. Windings should not touch the casing resulting in a defective coil. Pete
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