Sparking problem

[O mage]

adam quantrill said:

Lesliehedley said:

I do have a basic grasp of DC circuits and can follow a vehicle wiring diagram. ... If it is, then shouldn't the volt meter be applied on the coil positive terminal and the battery positive terminal, so that any voltage drop in the ignition switch side of the circuit due to a bad connection etc. registers on the meter?

You're on the right track!

It all boils down to Kirchoff's second law. You've got to make the measurements of the same circuit at the same time, it's not very useful measuring under the "earth lead test", then disconnecting, and measuring the battery voltage later.

adam quantrill said:

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.

Under point (a) you'll directly measure the volt drop, which could be low: If the battery condition is poor, it would explain the pull down to 10.5V under the coil -ve earth test, with no fault in the wiring.

FFS
There is no problem with the feed!. I really dont know why this is hard to understand and its starting to annoy me now.!

If you had the back off an ecu and you measure the feed voltage at 12 going in then you hook the harness up and check the circuit board and found the 5v feed out to the sensors would you say there is a problem with the feed??

It's Madness.!

You are measuring the circuit across the coil with the circuit complete.....You are no longer measuring the feed..!

[adam quantrill]

O mage said:

adam quantrill said:

Under point (a) you'll directly measure the volt drop, which could be low : If the battery condition is poor, it would explain the pull down to 10.5V under the coil -ve earth test, with no fault in the wiring.

FFS...

Emphasis added to make my meaning explicit.

[Penelope Stopit]

pk500 said:

Penelope Stopit you waisting your time and effort there too many experts who know everything about nothing and can argue with them self’s in a mirror same on fb forums too I started a friendly wedge group and don’t let them on you obviously know your thing

Thank you very much for your concern

Your comments have been taken in

Have never had anything to do with Facebook

Very much enjoy sharing my knowledge with posters here at PH TVR when they need help and also over at Technical, Computers and Electronics. Also enjoy Music and News forums

Was invited to join a Wedge Facebook Group in the past, posted my application to admin and was refused entry

Am one of the very few people that was banned from a Facebook Group before getting in, it was all so funny
Am laughing about it now as I type

Hoping that you are enjoying and keep enjoying your Wedge Group

Have a good day, stay safe

[O mage]

adam quantrill said:

O mage said:

adam quantrill said:

Under point (a) you'll directly measure the volt drop, which could be low : If the battery condition is poor, it would explain the pull down to 10.5V under the coil -ve earth test, with no fault in the wiring.

FFS...

Emphasis added to make my meaning explicit.

Im sorry its hard to keep up with different peoples changing opinions.. so can you please answer these questions directly.

1 Do you still think the op's problem is with the feed?
2 Do you think it should run ok as other vehicles do with the same 10.5v reading?
3 Should the op move on diagnostically?

[Penelope Stopit]

Lesliehedley said:

OK, I'm a bit confused. I'm not an expert of any kind but I do have a basic grasp of DC circuits and can follow a vehicle wiring diagram. What is confusing me is that I think in this post we are trying to decide if the coil ignition supply is ok or not. Now, by coil ignition supply, I assume you mean the voltage reaching the coil through the ignition switch, fuse, etc. Is this correct? If it is, then shouldn't the volt meter be applied on the coil positive terminal and the battery positive terminal, so that any voltage drop in the ignition switch side of the circuit due to a bad connection etc. registers on the meter? My understanding of DC circuits is that putting the meter across the coil is measuring the voltage drop due to the coils resistance. Have I got this totally wrong? What am I missing? I'm just trying to understand the basic theory involved here and I'm lost at the moment.

Most important thing to know is the battery voltage, once it's known to be good

Second most important thing to know, is the component good and of the correct voltage

Yes there is no problem measuring the voltage from the start of a cable run to the end of its run, obviously the cable must be under the load of the component it is supplying

Hence the ignition coil is earthed with a known to be good jumper cable

Another method is to measure the voltage at the battery and then at the component

Deducting the voltage at the component from the battery voltage also shows any volt-drop

It's all very simple basic electrical testing

[Penelope Stopit]

With the coil earthed Bigfish_74 commented

Bigfish_74 said:

Reading of 10.5v across the coil with that test. 12.5v at the battery

We must never forget

[adam quantrill]

Exactly, but what was never mentioned was whether the two readings were taken at the same time, I've been back through the posts.

[adam quantrill]

O mage said:

Im sorry its hard to keep up with different peoples changing opinions.. so can you please answer these questions directly.

1 Do you still think the op's problem is with the feed?
2 Do you think it should run ok as other vehicles do with the same 10.5v reading?
3 Should the op move on diagnostically?

I've been quite careful not to draw conclusions with insufficient information, and keep my mind open to the various possibilities, but I can answer (3), as I requested many posts ago - measure all relevant voltages [a-h], and post up the results.

[Penelope Stopit]

O mage said:

FFS
There is no problem with the feed!. I really dont know why this is hard to understand and its starting to annoy me now.!

If you had the back off an ecu and you measure the feed voltage at 12 going in then you hook the harness up and check the circuit board and found the 5v feed out to the sensors would you say there is a problem with the feed??

It's Madness.!

You are measuring the circuit across the coil with the circuit complete.....You are no longer measuring the feed..!

You are going off topic

Control unit voltages have nothing to do with this topic

You commented

O mage said:

Volts disappear and heat appears shall we just call it a magic box. The secondary in these automotive tesla coils is connected to the primary at the mid point of the primary inside the casing of the device you are testing. Does that help.?

Volts don't disappear

The secondary winding of the coil does not cause the primary coil supply to drop by 2 volts

Several times it has been commented that the information posted by myself is common knowledge and can be found at many reputable websites

You are unable to post how the secondary winding of an ignition coil drops the coil primary supply voltage by 2 volts

The reason why you are unable to reply or explain how you think the above can possibly take place is because it doesn't happen

If you could explain you would have

Apart from your child like comments that you posted earlier in this topic that by now may have been deleted, you are now resorting to abbreviated bad language

[O mage]

adam quantrill said:

O mage said:

Im sorry its hard to keep up with different peoples changing opinions.. so can you please answer these questions directly.

1 Do you still think the op's problem is with the feed?
2 Do you think it should run ok as other vehicles do with the same 10.5v reading?
3 Should the op move on diagnostically?

I've been quite careful not to draw conclusions with insufficient information, and keep my mind open to the various possibilities, but I can answer (3), as I requested many posts ago - measure all relevant voltages [a-h], and post up the results.

Ok If you had a similar vehicle in the same drive way and one was suffering the op's problem and one was running great and so you decide to measure and compare the two. So you see the 10.5v on the good one and you see the 10.5v on the bad one.

Now are you telling me that you cannot draw enough of a conclusion to move on diagnostically?

That is what has been done up to now in this thread by the power of observation and by the power of the internet..!

There is no point doing any of your further tests if you cannot conclude anything and move on.

[Penelope Stopit]

adam quantrill said:

Exactly, but what was never mentioned was whether the two readings were taken at the same time, I've been back through the posts.

Hence I made sure Bigfish wasn't misunderstanding anything by posting the following

---

Don't leave the coil powered up for too long, it will overheat

You comment single white wire from ignition which has a good 12.5v

Do you mean there is 12.5 volts at the white ignition supply cable that is connected to the coil + positive and that voltage drops to 10.5 volts when earthing the coil negative

If so

The ignition supply to the coil is dropping by 2 volts when under coil load......this is a fault

Apart from poor or burnt connections, the only other problem could be the fitting of the wrong voltage ignition coil

Some ignition circuits use a 9 or even 6 volt coil and a ballast resistor in series with the coil supply (White cable) to drop the voltage

Fitting a lower voltage coil in a 12 volt circuit could cause a volt drop to increase

---

Later there was a reply to the above

Bigfish_74 said:

You've convinced me, I'll work it back, maybe a fault at the relays. Thanks again.

[Penelope Stopit]

Hoping that KKson is ok

I posted the following

Penelope Stopit said:

Should 1000 posters all post here that the measured voltage at the 12 volt ignition coil supply was 10.5 volts when under coil load.......

The above would prove that there were 1000 TVR's known to have ignition coil supply problems

It's a fact

KKson replied with the following

KKson said:

Unfortunately "Penelope" I'm not sure I agree with this and to be honest I'm not getting into any form of argument. So both of my Wedges have around 9 volts at the coil with ignition on but engine not running. Whether that's right or wrong they both run without issue and they generate great big fat sparks. The 390SE had a VERY expensive rolling road session the other year and a full health check at the hands of probably the UK's leading expert in Rover and flapper EFi systems. The tests included voltage measurements, ECU measurements, timing etc etc.

I'm not an electrical expert but I think the original issues the OP is having may well have nothing to do with the coil voltage. My SEAC is also due for a full health check on the 3rd July at the hands of the same specialist (Mark Adams and Shropshire Automotive) so I will ask him the question as to what he considers the coil voltages should be.

I replied with the following in the hope that any confusion caused by posters mentioning 9 volt and 6 volt systems would no longer cause confusion

Penelope Stopit said:

No problem KKson

There is nothing to argue about, have posted up how to test an ignition coil circuit supply for a 12 volt ignition coil system.....meaning no ballast resistor

Some posters to this topic have commented that a 12 volt coils ignition supply can be expected to drop by 2 volts when the negative side of the coil is earthed.............this is not the case, it doesn't drop by more than fractions of a volt if in good order

Not one of the posters have explained how the voltage could possibly drop by 2 volts...........because it can't, if in good order

See below post for 9 volt ignition circuits

I then went to great lengths in explaining how a 9 volt system worked and what voltages were to be expected

KKson never did reply and I do hope all is ok

Edited by Penelope Stopit on Tuesday 16th June 13:53

[O mage]

Inside the device you are testing there are two coils wrapped around an iron core as the coil is turned on via the secondary terminal being switched to earth then voltage is pulled into the primary and secondary coils and so electromagnetism is built up in the iron core. This magnetic field then breaks down when the coil is switched off through the secondary. when it collapses a massive voltage is released from the core and down the king lead.

This action produces heat and the circuit should not really be over timed as it is being whilst doing the test

In operation the coil is only triggered for milliseconds.

I hope this helps you understand what is happening in the circuit you are testing.

[adam quantrill]

Penelope Stopit said:

adam quantrill said:

Exactly, but what was never mentioned was whether the two readings were taken at the same time, I've been back through the posts.

Hence I made sure Bigfish wasn't misunderstanding anything by posting the following

---

..

---

Later there was a reply to the above

Bigfish_74 said:

You've convinced me, I'll work it back, maybe a fault at the relays. Thanks again.

But was there a reply with an updated reading? I haven't seen one, although I must admit in between all the chaff it would be quite easy to miss.

[adam quantrill]

Penelope Stopit said:

Apart from poor or burnt connections, the only other problem could be the fitting of the wrong voltage ignition coil

I'll have to pick you up on this one point though, despite your posts being reasonably accurate, that these are not the only three possible problems.

At least other possibility remains is that the battery is low on charge or defective and the Vbat voltage drops to 10.5V or thereabouts at the point where the earth jumper is deployed and a large current draw starts.

This is why I specifically asked for battery condition tests in my list, and also to measure coil(+) to Bat (+) voltage explicitly (while the earth jumper is deployed).

[O mage]

The 2 volts in the magic trick is being stored by the coils in the core as magnetism and so is invisible to your meter.....Appears Disappears now you know how the trick is done you can open your bonnet and amaze your friends and family with it you could wave a magic wand over it for full effect and for the grand finalle you can present them with a hot pot of tea boiled in a jug by the coil itself. Imagine the look on their faces as they revere your magical prowess

[pk500]

Penelope Stopit said:

Thank you very much for your concern

Your comments have been taken in

Have never had anything to do with Facebook

Very much enjoy sharing my knowledge with posters here at PH TVR when they need help and also over at Technical, Computers and Electronics. Also enjoy Music and News forums

Was invited to join a Wedge Facebook Group in the past, posted my application to admin and was refused entry

Am one of the very few people that was banned from a Facebook Group before getting in, it was all so funny
Am laughing about it now as I type

Hoping that you are enjoying and keep enjoying your Wedge Group

Have a good day, stay safe

Your welcome to join the friendly wedge group knowledge is a good thing and a good help when people listen good luck on here sometimes you must have patience of a saint

[Penelope Stopit]

adam quantrill said:

Penelope Stopit said:

adam quantrill said:

Exactly, but what was never mentioned was whether the two readings were taken at the same time, I've been back through the posts.

Hence I made sure Bigfish wasn't misunderstanding anything by posting the following

---

..

---

Later there was a reply to the above

Bigfish_74 said:

You've convinced me, I'll work it back, maybe a fault at the relays. Thanks again.

But was there a reply with an updated reading? I haven't seen one, although I must admit in between all the chaff it would be quite easy to miss.

You make a very good point, this was also posted and read by Bigfish

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?

adam quantrill said:

Penelope Stopit said:

Apart from poor or burnt connections, the only other problem could be the fitting of the wrong voltage ignition coil

I'll have to pick you up on this one point though, despite your posts being reasonably accurate, that these are not the only three possible problems.

At least other possibility remains is that the battery is low on charge or defective and the Vbat voltage drops to 10.5V or thereabouts at the point where the earth jumper is deployed and a large current draw starts.

This is why I specifically asked for battery condition tests in my list, and also to measure coil(+) to Bat (+) voltage explicitly (while the earth jumper is deployed).

As posted above and again below

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?

adam quantrill said:

Exactly, but what was never mentioned was whether the two readings were taken at the same time, I've been back through the posts.

How could you have possibly been back through the posts?

If you had read the above posts that I've re-posted here in this post, you wouldn't be asking all these questions

Edited by Penelope Stopit on Tuesday 16th June 15:55

[Penelope Stopit]

pk500 said:

Penelope Stopit said:

Thank you very much for your concern

Your comments have been taken in

Have never had anything to do with Facebook

Very much enjoy sharing my knowledge with posters here at PH TVR when they need help and also over at Technical, Computers and Electronics. Also enjoy Music and News forums

Was invited to join a Wedge Facebook Group in the past, posted my application to admin and was refused entry

Am one of the very few people that was banned from a Facebook Group before getting in, it was all so funny
Am laughing about it now as I type

Hoping that you are enjoying and keep enjoying your Wedge Group

Have a good day, stay safe

Your welcome to join the friendly wedge group knowledge is a good thing and a good help when people listen good luck on here sometimes you must have patience of a saint

Thank you very much for the offer, may well take you up on it, I can't be contacted by email from here at PH, have had to remove my email address

Have noticed that you have a PM email contact button here at PH. If I was to PM you in the future would you see it, do you check your PH email?

Yes, know what you mean, I do have the patience but am no saint

[pk500]

Yes I get ph mail go to my email address