No spark

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SiJul
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No spark

Post by SiJul »

Hi
I would appreciate any help in resolving a no spark issue.
Car- 1963 Negative earth. Points.
Not much recent road use apart from about 30 + minutes stationary running to check all well after water pump and thermostat replacements.
Then on a later short 10 minute run to nearby petrol station to top up fuel etc, engine would not restart. Petrol station mechanic assessed failed coil and once replaced engine ran well on return short journey.
A few weeks later (after no further use) engine stuttered a bit on another outward 5 mile journey but was fine on return after a break.
Next day engine misfired going down hill and loss power at bottom. RAC attended and diagnosed points gap incorrect (which was adjusted) and advised new points etc. car ran well on final 2 miles of that return journey.
I have now replaced points (old points actually had a good appearance) and set gap to 14 thou but inadvertently left ignition on at one point during process and coil overheated which then blew out.
Coil (from ESM) and condenser also now replaced but still no spark at plug.
No spark from dizzy supply cable from coil while disconnected and put to earth whileq points opened by hand.
12 volts on white LT SW supply to coil. No volts on CB LT output from coil to dizzie.
Does the above suggest a defective replacement coil - it was very cheap? I am awaiting another coil to arrive - non ballast (is that correct type?) from another supplier.
Pending receipt of this next coil, have I have done all possible checks?
All and any input much appreciated.
Simon
oliver90owner
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Re: No spark

Post by oliver90owner »

Coil should pass about 4A when connected to battery and ground. If not coil is dead.

Easily checked - 12V will be present at the coil live side and zero volts on the ground side of the coil, but no current passing.
myoldjalopy
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Re: No spark

Post by myoldjalopy »

As above - there should be 12v at both sides of the coil when earthed by your multi-meter. A cheap coil is likely to let you down. Distributor Doctor is the man for quality ignition parts, including points and condensors. Hopefully your replacement coil will be all that's needed, although I would re-set the points gap to 15 thou while you are waiting and check all the connections are good and in the right order so the points can't short out.
SiJul
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Re: No spark

Post by SiJul »

Thanks.
When with ignition on I have 12 volts at input to coil I get 12 volts at output while it is disconnected to dizzy and zero at output when connected to dizzy. However when reconnecting (when power on) the output to the dizzy terminal I get a spark whilst connecting but then can find no voltage (& no volts between contact plate and earth.)
What this means may be blindingly obvious or predictable to you of course but unfortunately not to me!
SiJul
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Re: No spark

Post by SiJul »

I forgot to ask - any recommendations for a coil. I have ordered one but happy to have another. Carrying a spare now seems a good plan.
Reading through past threads it seems they all (?) come from China (like so many things good and bad) but there is wide choice, price range and type. Plus it appears new ones are more likely to be defective on receipt than old ones. Before this episode I have not had a replacement in 30 years.
simmitc
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Re: No spark

Post by simmitc »

Have you still got the very first coil that was diagnosed as faulty by the petrol station mechanic? (Incidentally, where are you located that filling stations still have mechanics and spare coil available? That really is quite something these days!) Anyway, your original symptoms could have been the coil, but might have been a condenser failing, which is more likely, so if you still have that coil, then it would be worth testing it.

Non ballast coil is correct for a standard car. If a coil designed for use with a ballast resistor was fitted, then it could burn out quite quickly.

As above, Distributor Doctor will supply a good coil.

If the coil is fully fitted, then you will see 12v on SW and 12v on the CB with points open, but probably near to 0v on CB when points closed as the power (term used loosely) flows to earth through the points rather than your meter.
myoldjalopy
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Re: No spark

Post by myoldjalopy »

So to follow the above advice further, with ignition 'on', check voltage at CB terminal of coil when points are open (or insulate them from each other by slipping a piece of card in between them). You should see 12v. But if not, it suggests the current is grounding in the dizzy. So then check the points are correctly fitted. The order on the spindle should be insulator, then the spring arm, then the condenser lead, then the LT lead, then the top insulator, then the washer and lastly, the nut.
SiJul
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Re: No spark

Post by SiJul »

Thanks for all the help so far. Great relief to get all your advice. I am beginning to suspect my installation of new points missed out an insulation washer. Will update tomorrow after checking and taking readings etc.
Re a replacement at the local garage - the coil came quickly via local motor factors! I do not have the first old coil much to my regret having now read the above and past threads.
oliver90owner
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Re: No spark

Post by oliver90owner »

I gave you one scenario which would prove the coil dead - but not necessarily good.

To test the coil to demonstrate it is good, hold the king lead close to an earth potential surface and fit a wire to ground from the earth side of the coil. Removing the connection from the coil should induce a spark from king lead to earth. If it is a fat blue spark, coil is good.

The coil needs to pass several amps to store sufficient energy for the spark. Unless it draws about 3-4A it may not be too top class. Sports coils (high energy sparks claimed) tend to draw more current, so heat up more quickly. Too little current and the spark energy will diminish as the engine revs rise towards maximum. The resistance of the winding will not change the voltage across the coil when connected to the 12V supply and disconnected at the earth side - unless reading zero (in which case it would be an open circuit through the coil).

You will not ground the coil with a multimeter set on volts. The multimeter impedance may well be of the order of 10 Mega Ohms for a digital instrument, although much less for an analogue meter. You really need a 10A current range to measure the coil current. Many multimeters have a maximum current range of 2O0 mA and are protected by a 2A, or less, fuse.
kennatt
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Re: No spark

Post by kennatt »

[quoteI am beginning to suspect my installation of new points missed out an insulation washer. ][/quote]
half way down posts Was about to suggest you have a look at this,its very easy to fit it wrongly ,even experienced owners have done so.
SiJul
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Re: No spark

Post by SiJul »

The problem is solved (& I hope nothing else is hidden to be found later). Big relief.
I had made the foolish error while changing the contacts of not putting the two wire terminals (one from the coil) in the right place with regard to the insulation sleeve. I did not appreciate the significance of fitting the newer style of contacts with a slightly different arrangement and took insufficient care. No wonder the symptoms.
I are hugely grateful for all the wisdom and advice which you have all provided and in such a timely manner. I have learnt a lot from all the very helpful information provided.
Many thanks.
Simon
myoldjalopy
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Re: No spark

Post by myoldjalopy »

Well done and good result! Nice easy fix too, in the end 8)
The single spark you were getting when attaching a live LT connection to the dizzy suggested some kind of earthing through the dizzy set-up.
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