Sparking problem

[Bigfish_74]

Penelope Stopit said:

When having 12.5 volts @ the battery and 10.5 volts at the coil

What voltage is there at the ignition switch supply in and ignition out?

I think I've narrowed it down to the white supply from ignition switch to ignition relay 1and 2 ( different wiring to yours, maybe later 1988) but need to get the dash off as wire seems to reduce down from switch to relay so a join somewhere behind there. Just struggling for time on it with job, home tutoring and sunny weather

[Bigfish_74]

Bristol ave fag said:

From what you see it does suggest the high tension is low have you got another amp you could try it takes alot of stick to switch and pull the primary down and if its fitted remote it must ave a good earth on the back casing.

[Bigfish_74]

Bristol ave fag said:

From what you see it does suggest the high tension is low have you got another amp you could try it takes alot of stick to switch and pull the primary down and if its fitted remote it must ave a good earth on the back casing.

Had 2 new Amps on, last one along with new dizzy, back to the original at the moment but not ruling out there being more than one problem and may well be swapping them around again.

[Bristol ave fag]

Bigfish_74 said:

Had 2 new Amps on, last one along with new dizzy, back to the original at the moment but not ruling out there being more than one problem and may well be swapping them around again.

Ok but you have checked the feed at 12v then you earth the coil. and measure it at 10.5v across the coil poles. disconnect the earth and it returns to 12v. It is the coil that is consuming that voltage as it should do, that is creating the load itself. There is no problem with the feed.

[Bigfish_74]

Bristol ave fag said:

Ok but you have checked the feed at 12v then you earth the coil. and measure it at 10.5v across the coil poles. disconnect the earth and it returns to 12v. It is the coil that is consuming that voltage as it should do, that is creating the load itself. There is no problem with the feed.

Fair point, but If it's not a wiring problem, I'm back to swapping out parts that I've previously swapped and nowhere to go. It's a real bamboozler this one 😵

[Bristol ave fag]

Bigfish_74 said:

Fair point, but If it's not a wiring problem, I'm back to swapping out parts that I've previously swapped and nowhere to go. It's a real bamboozler this one ??

It could be in the engine harness but its doubtful anyway you can find the other end of of the coil switching wire at the amp disconnect the amp put 12v down that wire and do the headlight bulb as load test at the other end. If that section of wiring is failing under load the bulb will only glow dim.

[Penelope Stopit]

Bigfish_74 said:

Penelope Stopit said:

When having 12.5 volts @ the battery and 10.5 volts at the coil

What voltage is there at the ignition switch supply in and ignition out?

I think I've narrowed it down to the white supply from ignition switch to ignition relay 1and 2 ( different wiring to yours, maybe later 1988) but need to get the dash off as wire seems to reduce down from switch to relay so a join somewhere behind there. Just struggling for time on it with job, home tutoring and sunny weather

Ok then

There will be a brown battery supply at the relay terminal 30, check its a good 12.5 volts supply

The ignition switch will be switching in the relay at relay terminal 86, relay terminal 85 will be earthed

The relay terminal 87 will very likely switch a supply to a fuse

The fuse will very likely supply the rev counter

The rev counter will very likely supply the ignition coil

Keep the faith, you will find that volt-drop

[Penelope Stopit]

Bristol ave fag said:

Ok but you have checked the feed at 12v then you earth the coil. and measure it at 10.5v across the coil poles. disconnect the earth and it returns to 12v. It is the coil that is consuming that voltage as it should do, that is creating the load itself. There is no problem with the feed.

Nonesense

The ignition coil like any other electrical component doesn't consume voltage, it does consume current

The battery voltage was measured at 12.5 volts yet there was only 10.5 volts at the ignition coil supply when correctly tested by applying a negative to the other side of the ignition coil

There is a 2 volt volt-drop in the ignition coil supply circuit

You have got to be having a laugh here, fortunately Bigfish_74 is looking for the cause of the volt-drop and will find it

[Penelope Stopit]

Wonder if someone has altered the ignition coil wiring and used too thin a cable

Coil ignition supply cable should be 14/0.30 (14 strands of 0.30mm diameter) 8.75 Amps current carrying capacity at a minimum

Edited by Penelope Stopit on Thursday 28th May 11:27

[Penelope Stopit]

The following gives an idea of expected volt-drop in the ignition coil supply cable

Calculated using a 3 Ohm primary resistance coil and a supply cable length of 3 meters

First calculation carried out using 14/0.30, 1.0mm², 8.75A - cable OD 2.6mm



Second calculation carried out using 28/0.30, 2.0mm², 17.5A - cable OD 3.3mm



Shows how manufacturers keeping the costs of loom production down can affect performance

[Bristol ave fag]

Penelope Stopit said:

Nonesense

The ignition coil like any other electrical component doesn't consume voltage, it does consume current

The battery voltage was measured at 12.5 volts yet there was only 10.5 volts at the ignition coil supply when correctly tested by applying a negative to the other side of the ignition coil

There is a 2 volt volt-drop in the ignition coil supply circuit

You have got to be having a laugh here, fortunately Bigfish_74 is looking for the cause of the volt-drop and will find it

It's quite simple electrical engineering. It a transformer.!.................You know what a 110v transformer is on a building site.? you put 240v in one end and out the other comes 110v ok?...And you would take a meter to the component/tool you have plugged in and it would read 110v...not 240v......It transformed it.!........ A 12v automotive transformer is small.....Your phone charger takes 240v and sends out 5v....The ecu drops 12v to 5 volts for some circuits..I really don't why this is so difficult for you to understand as you seem to have some knowledge.

[KKson]

Bristol ave fag said:

I really don't why this is so difficult for you to understand as you seem to have some knowledge.

Just got to comment on this but "Penelope" has been supporting the Wedge world and our various electrical gremlins for some time and as far as I am aware "her" knowledge and advice has been absolutely spot on every time. I'm not an electrical expert but from what I have read over the last year or two, "her" knowledge is extensive and I would generally trust the advice given. That's my view.

[Bristol ave fag]

KKson said:

Bristol ave fag said:

I really don't why this is so difficult for you to understand as you seem to have some knowledge.

Just got to comment on this but "Penelope" has been supporting the Wedge world and our various electrical gremlins for some time and as far as I am aware "her" knowledge and advice has been absolutely spot on every time. I'm not an electrical expert but from what I have read over the last year or two, "her" knowledge is extensive and I would generally trust the advice given. That's my view.

I respect that and im glad about that and i should have said great knowledge but i just didn't take kindly to what i was saying being called nonsense when i was trying to advise someone.

[KKson]

No problem.

Out of curiosity I will head down to my garage after I've completed my due "working from home" and measure the voltages at the coil on both my SEAC and 390SE to see what they are with ignition on. Cheers.

[Bristol ave fag]

KKson said:

No problem.

Out of curiosity I will head down to my garage after I've completed my due "working from home" and measure the voltages at the coil on both my SEAC and 390SE to see what they are with ignition on. Cheers.

Nice, ok if you start the car and let it idle and measure the voltage you should see 12v at the coil . now engine off with the ignition on and coil trigger side earthed you should see a drop across the 2 coil terminals to 10.5v. I think this is where the confusion lays in two different conditions.

[Penelope Stopit]

Bristol ave fag said:

KKson said:

No problem.

Out of curiosity I will head down to my garage after I've completed my due "working from home" and measure the voltages at the coil on both my SEAC and 390SE to see what they are with ignition on. Cheers.

Nice, ok if you start the car and let it idle and measure the voltage you should see 12v at the coil . now engine off with the ignition on and coil trigger side earthed you should see a drop across the 2 coil terminals to 10.5v. I think this is where the confusion lays in two different conditions.

There is no confusion whatsoever on my part

You keep avoiding all information that I have posted

The supply at the ignition coil needs to be as close as possible to battery voltage when the negative side of the coil is earthed

The only time that the voltage is found to be 3 or 6 volts lower than battery voltage is when measuring a ballast resistor circuits supply voltage at the coil

Have you even bothered to think what a ballast resistor circuit achieves ?

You are getting it all wrong

Why persist in posting about transformers ?

It doesn't make any difference whatsoever that an ignition coil is a transformer

The test that I suggested is a static test, no engine running and is a very simple test

The test proves if there is a good or poor supply to the ignition coil positive and it is the only possible way of proving it 100%

This information is common knowledge

Each time a coil supply voltage is lowered by increments of 1 volt the secondary voltage is lowered due to less current flow through the primary coil which then doesn't create a strong enough magnetic field

I suggest you do some studying

[Penelope Stopit]

KKson said:

Just got to comment on this but "Penelope" has been supporting the Wedge world and our various electrical gremlins for some time and as far as I am aware "her" knowledge and advice has been absolutely spot on every time. I'm not an electrical expert but from what I have read over the last year or two, "her" knowledge is extensive and I would generally trust the advice given. That's my view.

I'm touched and lost for words, need a drink now, back later, stay safe

[adam quantrill]

I'm finding this post quite confusing to follow, can someone summarise what the OP has actually measured?

Or if I summarise it, please correct me if I'm wrong, and/or fill in (a)-(g) if I've missed them somewhere.

1. Observed a weak spark at King lead (while cranking)
2. Observed a weak spark at plug lead.
3. Measured voltage across coil primary (+ to -) at 10.5V (ignition on, not cranking, coil -ve earthed to battery)
4. Battery voltage 12.5V (ignition on, not cranking)

Has OP measured:

a) voltage between coil + supply and battery + (coil -ve earthed)?
b) voltage between coil - supply and engine block during cranking?
c) voltage between coil - supply and battery - during cranking?
d) battery voltage when cranking?
e) voltage between battery - and engine block while cranking?
f) battery voltage with headlamps on?
g) Spark quality (or does it run) when the coil + is taken direct to battery +?

As it might be useful to check the earthing and battery condition too.
While 10.5V at the coil supply isn't ideal, a car will run lower than that, I've seen it myself when the alternator packed up.

[Penelope Stopit]

adam quantrill said:

I'm finding this post quite confusing to follow, can someone summarise what the OP has actually measured?

Or if I summarise it, please correct me if I'm wrong, and/or fill in (a)-(g) if I've missed them somewhere.

1. Observed a weak spark at King lead (while cranking)
2. Observed a weak spark at plug lead.
3. Measured voltage across coil primary (+ to -) at 10.5V (ignition on, not cranking, coil -ve earthed to battery)
4. Battery voltage 12.5V (ignition on, not cranking)

Has OP measured:

a) voltage between coil + supply and battery + (coil -ve earthed)?
b) voltage between coil - supply and engine block during cranking?
c) voltage between coil - supply and battery - during cranking?
d) battery voltage when cranking?
e) voltage between battery - and engine block while cranking?
f) battery voltage with headlamps on?
g) Spark quality (or does it run) when the coil + is taken direct to battery +?

As it might be useful to check the earthing and battery condition too.
While 10.5V at the coil supply isn't ideal, a car will run lower than that, I've seen it myself when the alternator packed up.

Just a quickie, must get other things sorted

Yes coil negative earthed @ battery and coil positive supply measured while under coil load, static test, only possible way of getting an accurate reading of coil supply voltage

Battery voltage = 12.5

Coil supply = 10.5

= Go no further, there is definitely a 2 volt volt-drop in the coil supply cable that needs reducing to below 1 volt 0.5 volts give or take

Volt-drop can't be ignored and no further work can be carried out until it's sorted

Reason - excessive volt drop could be creating heat at a connection, in a relay or through the rev counter loop (if it has one), there could even be a partial short through a corroded bare cable

Car could go on fire

Such is life, it's nothing new, it doesn't even matter if engine performs well

Volt-drop must be reduced

It's common knowledge

Tables above show what can be achieved with supply voltage to coil by uprating the cable from 14 strand to 28 strand

Sorry but must go

[Bristol ave fag]

adam quantrill said:

I'm finding this post quite confusing to follow, can someone summarise what the OP has actually measured?

Or if I summarise it, please correct me if I'm wrong, and/or fill in (a)-(g) if I've missed them somewhere.

1. Observed a weak spark at King lead (while cranking)
2. Observed a weak spark at plug lead.
3. Measured voltage across coil primary (+ to -) at 10.5V (ignition on, not cranking, coil -ve earthed to battery)
4. Battery voltage 12.5V (ignition on, not cranking)

Has OP measured:

a) voltage between coil + supply and battery + (coil -ve earthed)?
b) voltage between coil - supply and engine block during cranking?
c) voltage between coil - supply and battery - during cranking?
d) battery voltage when cranking?
e) voltage between battery - and engine block while cranking?
f) battery voltage with headlamps on?
g) Spark quality (or does it run) when the coil + is taken direct to battery +?

As it might be useful to check the earthing and battery condition too.
While 10.5V at the coil supply isn't ideal, a car will run lower than that, I've seen it myself when the alternator packed up.

Yes you have the jist of it,yes try a feed off the battery direct, that's the first thing i would have done if id suspected the feed but i didnt suspect a the feed. He has already proved that the feed has 12v and can carry the 5amp to light the bulb steady so he has a good feed. A good feed dosn't do any more than that. If it was failing under coil load it would fail to light the bulb as they both pull 5 amp.
I think the problem is elsewhere so i suggested checking the trigger feed from the amplifier to see if that could be breaking down under load.

Edited by Bristol ave fag on Thursday 28th May 18:17

Edited by Bristol ave fag on Thursday 28th May 18:18