Dodgy coil?

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Jeremy
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#1 Dodgy coil?

Post by Jeremy » Tue Mar 05, 2019 5:45 pm

Not so exciting but might help someone.....

I started experiencing minutely short stutters from the engine a few weeks ago when running at high speed and accelerating hard. These were not significant jolts, but just momentary hesitations. The engine has done about 1500 miles since a total rebuild by Rob Beere and is otherwise running beautifully.

I discussed with Angus who suggested:
1. Coil
2. Distributor - go back to original points (Rob fitted a Petronix ignitor contactless breaker)
3. Fuel (I fitted a Filter King so wondered whether I had set the pressure limiter too low)
In that order, and do only ONE THING AT ONCE.

So yesterday I got round to swapping out the coil for the spare. Took the car for a run including a 10 mile burst on the motorway and a few charges up to 4000 rpm and the problem seems to be solved.

I called Rob this morning and got a bit more advice/info which was interesting:
1. He has lately come to the conclusion that Lucas sport coils are complete crap. That's interesting cos that's what he originally fitted to my engine.
2. The Intermotor sport coil is the only one he now uses. That's also interesting as that was the spare that he supplied me with a few months ago, and that I swapped in yesterday.
3. the Ignitor generally either works or doesn't
4. Fuel starvation at high load is usually evidenced by the engine being unable to deliver any more shove, rather than stuttering.
5. If you disconnect the outlet pipe from the Filter King and run it into a jug, you should get 1 pint in about 20 secs, or 30 secs at worst, to be sure it will keep a normal (untuned) engine supplied at full power, and the Filter King pressure should be set to between 2 and 4 psi.

I will do those checks on the fuel line when I get a moment, but meanwhile I'm hoping that it's the coil that was faulty.

Hope this might be helpful to others.

Oh - Angus, your consultancy fee invoice doesn't seem to have arrived yet... 8-)
Jeremy
1967 S1 4.2 FHC

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mgcjag
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#2 Re: Dodgy coil?

Post by mgcjag » Tue Mar 05, 2019 6:11 pm

Hi Jeremy....had very similar problems.....nearly drove me mad trying to find it.....finaly traced it down to a bad connection on one of the wires into the spade terminal that connects to the coil....very intermittant..only found it when i pulled the wire and it came out of the spade connector....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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1954Etype
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#3 Re: Dodgy coil?

Post by 1954Etype » Tue Mar 05, 2019 7:08 pm

Interesting comments from Rob. I’ll go with the intermotor coil in future. I’m still working out my latest holiday destination before sending you the fee Jeremy....
Angus 67 FHC 1E33656
61 OTS 875047

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Tom W
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#4 Re: Dodgy coil?

Post by Tom W » Tue Mar 05, 2019 7:37 pm

I had a similar problem, but the cause was something different. My car would stumble at speed, then pick up again as if nothing had happened. Something was interrupting the ignition. I finally found it was a dodgy Lucas relay in the circuit for the alternator. The relay was arcing and causing the voltage regulator to “see” a reduced voltage. Consequently, the alternator was putting a higher than normal voltage into system. Occasionally, the voltage would spike higher than the 123 distributor was rated for, causing it to cut out.
Tom
1970 S2 FHC

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Gfhug
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#5 Re: Dodgy coil?

Post by Gfhug » Tue Mar 05, 2019 8:10 pm

Jeremy “running at high speed”? That’ll be 70 mph? :wink:
S2 FHC Light Blue
S2 OTS LHD - RHD full restoration

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Richardhealey
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#6 Re: Dodgy coil?

Post by Richardhealey » Tue Mar 05, 2019 8:21 pm

Hi Jeremy,
To add to the collective knowledge (perhaps!) I had exactly the same symptoms you describe from a Tr6. It was the coil and the replacement would last for about a year, before the same thing would occur.
I think this was related to the positioning of the coil to the engine (it’s bolted to the block) and heat stress. I never bothered to relocate it for aesthetic reasons and perhaps I should have introduced some heat shielding, but I got lazy and coils aren’t too expensive...
Cheers,
Rich
1969 series 2, 2+2... going for a full rebuild.. Gulp...

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Herzeg
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#7 Re: Dodgy coil?

Post by Herzeg » Tue Mar 05, 2019 10:38 pm

Jeremy

Two years ago Angus fitted a Pertronix to mine when he did the RHD conversion. I had misfiring problems that got worse when running at higher revs. Eventually couldn't get it over 3,000rpm. Took it to a rolling road, where he swapped the coil and got it to 4,000rpm without misfires, and pronounced my coil as terminally ill.

Angus fitted a new coil and went back to traditional points, no further problem. It seemed the unit was wrecking the coil. I know others will disagree with me but junk the Pertronix is my view. I haven't had a problem in two years since.

John
1969 S2 OTS

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malcolm
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#8 Re: Dodgy coil?

Post by malcolm » Wed Mar 06, 2019 9:27 am

I had a similar situation with a Petronix-type system, at high revs. Turned out the plug/coil leads were interfering with the unit, with the field they set up. Changed the leads to silicone ones, and problem was instantly solved.
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S
2015 F Type V6 S

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Jeremy
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#9 Re: Dodgy coil?

Post by Jeremy » Wed Mar 06, 2019 11:05 am

Interesting to hear any other views on Pertronix. Maybe I should indeed switch back to trad points...as Angus pointed out, easier to carry a spare set and swap out in the event of problems too.

Geoff... Of course - I should have said "when dawdling along at 75"...
Jeremy
1967 S1 4.2 FHC

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AshM
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#10 Re: Dodgy coil?

Post by AshM » Wed Mar 06, 2019 1:09 pm

Thanks Jeremy - useful reference post.

I fitted the Lucas Sports Coil when I upgraded to 123 a couple of years ago. All great so far but will keep this in mind if I start to get problems.

cheers
Ash
Series 2 FHC 1970
1R 20607

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Marcus2571
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#11 Re: Dodgy coil?

Post by Marcus2571 » Wed Mar 06, 2019 1:37 pm

I've got the same story... running along at 71mph and engine misfires, stumbles along and then stalls. Will have been happy for previous 150-300 miles and then this happens out of nowhere.

Replaced electronic ignition with points but does still happen...

Has anyone else found their coil gets hot (like an almost fresh cup of coffee hot)?

What ohm rating should the coil be?

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cactusman
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#12 Re: Dodgy coil?

Post by cactusman » Wed Mar 06, 2019 1:42 pm

While I am not saying coils never fail it is much more likely to be cabling or points etc. Coils have no moving parts and most are oil filled. If the primary or secondary fails open circuit then you stop. If the thing breaks down internally the car will run roughly (or stop) but most likely across the whole rev range and may be hard to start...in my experience in my experience coils are often blamed when actually the fault lies elsewhere. I suspect my MGB coil is 53 years old....and is fine.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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Jeremy
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#13 Re: Dodgy coil?

Post by Jeremy » Wed Mar 06, 2019 2:01 pm

Hmm ...well....i will update this post when I've done some more miles.
Jeremy
1967 S1 4.2 FHC

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mgcjag
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#14 Re: Dodgy coil?

Post by mgcjag » Wed Mar 06, 2019 2:51 pm

To Marcus a few posts up......what model do you have..please try to put it in the signature area with your name..thanks.....re hot coil...sounds too hot......is you car useing ballast resistor....have you got the correct coil fitted..if not it will overheat.....look here..http://forum.etypeuk.com/viewtopic.php? ... resistance Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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cactusman
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#15 Re: Dodgy coil?

Post by cactusman » Wed Mar 06, 2019 3:18 pm

If you used a coil for a ballast resistor system in a car without a ballast system then, yes, the coil will soon overheat and fail
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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malcolm
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#16 Re: Dodgy coil?

Post by malcolm » Thu Mar 07, 2019 9:13 am

Jeremy wrote:
Wed Mar 06, 2019 11:05 am
Interesting to hear any other views on Pertronix. Maybe I should indeed switch back to trad points...as Angus pointed out, easier to carry a spare set and swap out in the event of problems too.

Geoff... Of course - I should have said "when dawdling along at 75"...
With the Simonbbc powerspark, it's dead easy to switch back to points on the road in 5 mins if you have a problem, and the powerspark means that you never worry about gaps, maintenance etc. Never had a problem since fitting silicone leads, but carry the points in case.
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S
2015 F Type V6 S

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Jeremy
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#17 Re: Dodgy coil?

Post by Jeremy » Tue Apr 02, 2019 7:34 pm

Couple of hundred miles later and the misfiring hasn't come back....
Lovely day out yesterday in the Chilterns :thumbsup:

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Jeremy
1967 S1 4.2 FHC

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johnetype
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#18 Re: Dodgy coil?

Post by johnetype » Thu Apr 04, 2019 11:20 pm

When you fit a set of electronic points such as a Petronix, Simon BBC or similar they open more quickly than a mechanical set of points which is deliberate and beneficial as this faster opening gives a steeper rise time and a higher voltage spike from the coil. It's one of the two ways electronic points are beneficial over mechanical ones.

However the greater voltage now generated by the coil gives greater opportunity for breakdowns anywhere between the coil output and the spark plug connector, which lead to misfires. Hence the recommendation to fit silicone spark plug leads by some electronic points suppliers and as Malcolm found by experience.

Series 3 XJ6's and their XK engine with electronic ignition have silicone plug leads as supplied by the factory with good reason, PVC copper wire plug leads with resistor plug caps are marginal for any engine with electronic ignition.
John

1969 Series 2 FHC

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#19 Re: Dodgy coil?

Post by mgcjag » Fri Apr 05, 2019 7:55 am

Hi John....I keep seeing these references to useing "Silicone" spark plug leads......but what are we actually talking about.......Silicone is not the conductor its just the external insulation......Silicone leads can either have a carbon or a copper core......Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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malcolm
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#20 Re: Dodgy coil?

Post by malcolm » Fri Apr 05, 2019 8:14 am

I've wondered about that Steve - what I found with mine is that you can't test continuity on my leads with a meter! So obviously not copper cored. Not sure how they conduct electricity without being "checkable" on a meter. Bit of a nuisance if you're trying to trace a break in the wiring! I just know they seem to work.
Malcolm
I only fit in a 2+2, so got one!
1969 Series 2 2+2
2009 Jaguar XF-S
2015 F Type V6 S

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