Ignition Coils
Discussion
Thanks Mark, true to Wesley's latest form it started cutting out again after 5 miles or so. I reached home and the coil was far to hot to touch. So, today I've put another coil on with a switched supply to an external ballast resistor, the other side to the + terminal on the coil. Running up to temperature the coil reached between 55-60 degrees C. I think both coils I've been given must be 9 volt ones hence the "too hot to handle". So hopefully with the resistor in the circuit and a direct switched 12 volt supply it will keep the coil operating. I never realized that coils get quite hot during running? J C.
Further to my last post Mark. I did some voltage checks whilst at work and indeed with the present connections ie switched 12v supply to the ballast resistor and at the + coil connection 9v. However interestingly there is a constant voltage supply reading with the negative multimeter lead touching the coil casing? Obviously with the ignition on. Is that right? Not long enough run in to work to reproduce the original fault. J C.
...
John042 said:
Further to my last post Mark. I did some voltage checks whilst at work and indeed with the present connections ie switched 12v supply to the ballast resistor and at the + coil connection 9v. However interestingly there is a constant voltage supply reading with the negative multimeter lead touching the coil casing? Obviously with the ignition on. Is that right? Not long enough run in to work to reproduce the original fault. J C.
I didn't want to jump in and post here earlier as the question was posted to MarkSeveral times here at PH TVR something similar has been mentioned, the majority of TVR owners suggest the earthing of the coil case or its mounting bracket
I was puzzled by this as I didn't think any coils needed earthing and took them to be insulated......In summary - some coils do need earthing and the fact that your coils case is showing a voltage suggests that it needs earthing or is faulty
Thanks Adam. Apparently talking to various old Brit' car owners coil problems are not uncommon. 9 volt coils with ballast resistors were common with mechanical contact breaker systems. and there are good coils and not so good ones. Consensus of opinion is that since mine have been "cooking" (Over Heating) some internal damage could have occurred. The recommended option is to replace with a good quality coil such as "Flame Thrower" Lets face it I've replaced every other component in the system.
Your suggestion of an additional earth might also be worth considering. In fact to night I'll connect a lead on to the coil clamp and earth it. A short run in to work may reveal a cool coil? Cheers J C.
Your suggestion of an additional earth might also be worth considering. In fact to night I'll connect a lead on to the coil clamp and earth it. A short run in to work may reveal a cool coil? Cheers J C. adam quantrill said:
Hmm, if the coil is insulated where does the spark come from, and go to?
You probably need to read up on induction coils.
Take a look at this, this is how I thought all coils were internally wired until a few posters here mentioned an earth to the coils caseYou probably need to read up on induction coils.
Earthing a coil to make it work really did confuse me until someone posted me a diagram of a different type of coil that had an internal earth connection, I think it is the older variety of coils that have an internal earth
This is the great thing about forums, there is so much to learn
No Earth
No Earth
No Earth
Edited by Penelope Stopit on Tuesday 5th June 20:59
Thanks Adam. With our Wedges I think the "Swiching" of the coils primary windings is insigated by the dissy from the negative coil terminal and controlled by the ignition module completing the circiut? Thereby inducing HT current in the secondary coil windings.Still it can't hurt earthing the coil case? On a "normal" metal car this would be achieved through its mounting? J C
I think it's essential to earth the case, or else the return path for the 20-30kV spark has to travel up the primary somehow. As in Penny's dodgy diagrams.
This cannot be good (having no earth) because usually on a wedge there's an electronic circuit driving the coil primary (the ignition amplifier) and in the case of the V8, the primary also goes to the tacho and the ECU.
Each of these items could easily get fried if you get spark voltages getting into them.
If you look on the V8 there's a flimsy braid from the coil clamping bracket to the block (alternator bracket). I don't like this braid, it gets corroded, and drops off on one end or the other, or is easily broken. I have supplemented it with a stout copper wire on my installation, trapped under the bracket on the coil end and clamped onto the alternator mounting bolt.
This cannot be good (having no earth) because usually on a wedge there's an electronic circuit driving the coil primary (the ignition amplifier) and in the case of the V8, the primary also goes to the tacho and the ECU.
Each of these items could easily get fried if you get spark voltages getting into them.
If you look on the V8 there's a flimsy braid from the coil clamping bracket to the block (alternator bracket). I don't like this braid, it gets corroded, and drops off on one end or the other, or is easily broken. I have supplemented it with a stout copper wire on my installation, trapped under the bracket on the coil end and clamped onto the alternator mounting bolt.
Coils -
It's not true that the high voltage part is linked to the case, or at least not on the coils I've seen.
if you test it with a multimeter, you will see the case isn't connected to any of the terminals.
The 'other' side of the high voltage (spark) coil goes to the +ve of the coil. Yes, really. test it with your meter.....
In the grand scheme of things when you get about 25,000 volts (or more), whether it's connected to Earth or the 12V
doesn't make any real difference. With the original points, the points switched the earth of the coil (as per Penelope S diagram),
but the +ve side stays connected.
So the spark voltage actually goes via the battery to the engine block. As the battery doesn't see the voltage (as it sparks across the plug...) and the current
is actually tiny, it all works out nicely.
But while earthing the coil might help with radio reception, it's not actually necessary.
NB. The 'wasted spark' type coil packs in later EFi systems actually connect BOTH sides of the spark coil to a spark plug, so BOTH plugs actually spark,
but only one is correct for actual ignition, the other is whilst exhaust is happening - hence "wasted spark" .....
(e.g. 3 coils for 6 plugs.....)
It's not true that the high voltage part is linked to the case, or at least not on the coils I've seen.
if you test it with a multimeter, you will see the case isn't connected to any of the terminals.
The 'other' side of the high voltage (spark) coil goes to the +ve of the coil. Yes, really. test it with your meter.....
In the grand scheme of things when you get about 25,000 volts (or more), whether it's connected to Earth or the 12V
doesn't make any real difference. With the original points, the points switched the earth of the coil (as per Penelope S diagram),
but the +ve side stays connected.
So the spark voltage actually goes via the battery to the engine block. As the battery doesn't see the voltage (as it sparks across the plug...) and the current
is actually tiny, it all works out nicely.
But while earthing the coil might help with radio reception, it's not actually necessary.
NB. The 'wasted spark' type coil packs in later EFi systems actually connect BOTH sides of the spark coil to a spark plug, so BOTH plugs actually spark,
but only one is correct for actual ignition, the other is whilst exhaust is happening - hence "wasted spark" .....
(e.g. 3 coils for 6 plugs.....)
Edited by RCK974X on Wednesday 6th June 00:25
Coils - low voltage side.
As far as I know there are 12v coils, 9v coils and 6v coils.
I think Ford use 9v coils ??? (not sure).
So for normal engine running there is a resistor (the infamous Ford 'blue wire') connected in series with the coil to drop the voltage.
This resistor is shorted out when cranking the engine with the switch on the starter motor, (which is also used as a 'signal' on many
injection systems) so it boosts the spark when cranking (as the battery voltage can drop quite a lot....)
on the 2.8 engine, this starter motor switch turns on the start injector too.....
As far as I know there are 12v coils, 9v coils and 6v coils.
I think Ford use 9v coils ??? (not sure).
So for normal engine running there is a resistor (the infamous Ford 'blue wire') connected in series with the coil to drop the voltage.
This resistor is shorted out when cranking the engine with the switch on the starter motor, (which is also used as a 'signal' on many
injection systems) so it boosts the spark when cranking (as the battery voltage can drop quite a lot....)
on the 2.8 engine, this starter motor switch turns on the start injector too.....
adam quantrill said:
Hmm, if the coil is insulated where does the spark come from, and go to?
You probably need to read up on induction coils.
You probably need to read up on induction coils.
adam quantrill said:
I think it's essential to earth the case, or else the return path for the 20-30kV spark has to travel up the primary somehow. As in Penny's dodgy diagrams.
This cannot be good (having no earth) because usually on a wedge there's an electronic circuit driving the coil primary (the ignition amplifier) and in the case of the V8, the primary also goes to the tacho and the ECU.
Each of these items could easily get fried if you get spark voltages getting into them.
If you look on the V8 there's a flimsy braid from the coil clamping bracket to the block (alternator bracket). I don't like this braid, it gets corroded, and drops off on one end or the other, or is easily broken. I have supplemented it with a stout copper wire on my installation, trapped under the bracket on the coil end and clamped onto the alternator mounting bolt.
Where you having a bad day yesterday? I am attempting to help you understand how a contact set driven ignition system works as it has become obvious that you don'tThis cannot be good (having no earth) because usually on a wedge there's an electronic circuit driving the coil primary (the ignition amplifier) and in the case of the V8, the primary also goes to the tacho and the ECU.
Each of these items could easily get fried if you get spark voltages getting into them.
If you look on the V8 there's a flimsy braid from the coil clamping bracket to the block (alternator bracket). I don't like this braid, it gets corroded, and drops off on one end or the other, or is easily broken. I have supplemented it with a stout copper wire on my installation, trapped under the bracket on the coil end and clamped onto the alternator mounting bolt.
In one post you have suggested that I probably need to read up on induction coils
In another post you make a remark about a diagram I posted being dodgy
I don't know and don't wish to know what gives you an adult the motivation to attempt to rewrite how an ignition system works so as to prove the diagrams I have posted as being wrong, all the information I have posted here is fact
Relax and enjoy, don't worry be happy, here are some more diagrams that may help you understand how an ignition system works
The fact that you have for very likely many years misunderstood how an ignition system works is no big deal
Many people don't understand how an ignition system works, I didnt understand it until I did
Take note that the first 2 x diagrams show contact set driven ignition and the coil secondary winding connects from the capacitor/points side of the coil to the spark plug
The bottom diagram shows the secondary winding connected to the supply side of the coil but this circuit doesn't use a capacitor
Edited by Penelope Stopit on Thursday 7th June 22:01
celcius said:
Hi mr stopit, im having motor vehicle college tech flash backs , lol
This is very interesting because I was having the same as I typed thee aboveI will never forget the day when the head of the automotive electrical section walked in during a lecture to listen to a tutors teaching....The main man witnessed the tutor telling us that the secondary coil (HT Voltage) travelled around the vehicles 12 volt system, main man went ballistic with the tutor for talking such nonesense while being paid to do so
I was more shocked than anything else until I later found it hilarious, the tutor wasn't a very nice man
Go steady with your flashbacks as they can have a shocking influence on your day
Here is a nice PDF file for anyone interested in this stuff http://beru.federalmogul.com/sites/default/files/t...
Edited by Penelope Stopit on Wednesday 6th June 08:46
After those posts, Just in case, I'll make as clear as I can -
How many posters here think that the high voltage spark goes through the capacitor to the engine block when the points open ??
because if you do...... You are wrong......
If you're an old codger like me, you will remember when those condensors had "0.1 UF 250V" stamped on them.....
not quite up to the 25,000 volts for a spark then......
[Clue - hasn't it dawned on any of the bright sparks here that even if the HT coil *IS* connected to the points side,
it is *still* connected the the +12v side via the low voltage coil ?]
How many posters here think that the high voltage spark goes through the capacitor to the engine block when the points open ??
because if you do...... You are wrong......
If you're an old codger like me, you will remember when those condensors had "0.1 UF 250V" stamped on them.....
not quite up to the 25,000 volts for a spark then......
[Clue - hasn't it dawned on any of the bright sparks here that even if the HT coil *IS* connected to the points side,
it is *still* connected the the +12v side via the low voltage coil ?]
RCK974X said:
Coils -
It's not true that the high voltage part is linked to the case, or at least not on the coils I've seen.
if you test it with a multimeter, you will see the case isn't connected to any of the terminals.
The 'other' side of the high voltage (spark) coil goes to the +ve of the coil. Yes, really. test it with your meter.....
So the spark voltage actually goes via the battery to the engine block. As the battery doesn't see the voltage (as it sparks across the plug...) and the current
is actually tiny, it all works out nicely.
It's not true that the high voltage part is linked to the case, or at least not on the coils I've seen.
if you test it with a multimeter, you will see the case isn't connected to any of the terminals.
The 'other' side of the high voltage (spark) coil goes to the +ve of the coil. Yes, really. test it with your meter.....
So the spark voltage actually goes via the battery to the engine block. As the battery doesn't see the voltage (as it sparks across the plug...) and the current
is actually tiny, it all works out nicely.
RCK974X said:
After those posts, Just in case, I'll make as clear as I can -
[Clue - hasn't it dawned on any of the bright sparks here that even if the HT coil *IS* connected to the points side,
it is *still* connected the the +12v side via the low voltage coil ?]
I was finding your input interesting until you moved the goal posts as in your above comment[Clue - hasn't it dawned on any of the bright sparks here that even if the HT coil *IS* connected to the points side,
it is *still* connected the the +12v side via the low voltage coil ?]
You have now back tracked on your first post that stated the secondary winding connects to the coils supply
You now state that the secondary winding being connected to the coils points side also connects to the coils supply side through its primary winding and me saying that you are now stating the obvious is an understatement
Although it is you that has back tracked on your theory of how an ignition system works you then go on to use the words "bright sparks" when refering to other posters
Back tracking in an attempt to cover your earlier incorrect comments is a no goer
You have put very little importance on the fact that changing from your first thoughts on how an ignition coil is internally wired to how the majority of them are internally wired as in my above diagrams
There is a massive difference between internally connecting the secondary winding to the points side or the supply side
Keep digging a hole for yourself but please don't post this "bright sparks" nonesense and then back track on your earlier comments as that isn't a very bright thing to do is it
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