Will only start after ignition key is released?

[rdl001]

1996 Chim,
Having recently fitted a new Bosch Coil (TVR E0057) and Ignition Module (TVR E0411) from TVR parts Ltd, my engine is running so much better, particularly at higher rpm. Note: The old Lucas coil (now replaced with the Bosch) has a very high resistance and the old Lucas Ignition module (now replaced with a copy part) looks like the original.

But I have one niggling problem, that now the engine will not start until I release the key from position 3 (cranking and coil) to position 2 (run). When it cranks I am seeing about 9-10 volts. When the engine is off I see 12.8 volts, when the engine is running I see 13.5 volts. The starter motor turns very quickly, just won't start until I let go of the key.


Note: The old Lucas coil (now replaced with the Bosch) has a very high resistance and the old Lucas Ignition module (now replaced with a copy part) looks like the original.

I am pondering whether to change back to the old Lucas ignition module, any thoughts would be much appreciated.

Regards,

[5.0ltr]

I have no idea and electrics are not my field but will throw this in helpful or not. A few years ago I had a car that would do something similar and would do this infrequently, it happened to let me down one night and I found a small garage still open, described the fault and he sold me a new ballast resistor that fitted on the coil and it fixed the problem.

[rdl001]

Thanks 5ltr, but I am pretty sure that there is no ballast resistor used in this engine circuit.

[Belle427]

Did the fault occur immediately after putting the replacement parts in?

[rdl001]

Yes, not quite immediately but after 3-4 start ups.

The car is running so much better with this new coil and module, I am reluctant to change them back but I may need to for diagnosis purposes.

I always worry when making repairs/modes/ upgrades etc that it's easy to disturb something else which can be totally unrelated.

[Belle427]

Certainly sounds like a voltage drop to the coil somehow.

[Oldred_V8S]

Belle427 said:

Certainly sounds like a voltage drop to the coil somehow.

9-10v is normal whilst cranking

[CAPP0]

Is it the 14CUX system on your engine? To me that sounds like a dodgy ignition amplifier, I had this on a RRC with the same engine. Try either swapping your old one back, or get a(nother) new one, best to go for decent quality, def not Britpart if that's what you have got. I think a good source is simonbbc.com (no affiliation, just a customer!)

[Penelope Stopit]

rdl001 said:

1996 Chim,

But I have one niggling problem, that now the engine will not start until I release the key from position 3 (cranking and coil) to position 2 (run). When it cranks I am seeing about 9-10 volts. When the engine is off I see 12.8 volts, when the engine is running I see 13.5 volts. The starter motor turns very quickly, just won't start until I let go of the key.

Were the above voltage readings taken at the battery?

If the answer is yes

You need to take voltage readings at the ignition coil positive with...

1) Ignition on

&

2) During cranking

A faulty ignition switch, alarm or immobiliser will cause this fault

Carrying out the above tests may show that there is no ignition supply to the ignition coil during cranking

[Loubaruch]

This may be a red herring but worth measuring the voltage at the ignition position on the ignition switch and see if it stays live in the cranking position.

I had the same problem on another car and found that the ignition switch lost its ignition feed in the cranking position so would only start when I stopped cranking.

[rdl001]

Thanks Penolope,

Ahh, now when I measure the voltage at the coil I get:
1) Ignition on - 0 volts

2) During cranking - 3.3 volts

Any more thoughts?

[Belle427]

Double check all the connections around the coil area, its a bit of a mess there and easy to disturb.

[Penelope Stopit]

Penelope Stopit said:

rdl001 said:

1996 Chim,

But I have one niggling problem, that now the engine will not start until I release the key from position 3 (cranking and coil) to position 2 (run). When it cranks I am seeing about 9-10 volts. When the engine is off I see 12.8 volts, when the engine is running I see 13.5 volts. The starter motor turns very quickly, just won't start until I let go of the key.

Were the above voltage readings taken at the battery?

If the answer is yes

You need to take voltage readings at the ignition coil positive with...

1) Ignition on

&

2) During cranking

A faulty ignition switch, alarm or immobiliser will cause this fault

Carrying out the above tests may show that there is no ignition supply to the ignition coil during cranking

rdl001 said:

Thanks Penolope,

Ahh, now when I measure the voltage at the coil I get:
1) Ignition on - 0 volts

2) During cranking - 3.3 volts

Any more thoughts?

My apologies for not explaining the above test more clearly, I've got a feeling that 3.3volts was measured with a multimeter (set to volts DC) connected across the ignition coil positive and negative terminals (my gut feeling could be wrong)

Should have advised to...............

Connect Multimeter (set to volts DC) black negative cable to battery negative post or known good engine earth

Connect Multimeter red positive cable to ignition coil positive terminal (Leaving ignition coil connected as is)

What voltage readings show with

1) Ignition on

&

2) During cranking

A faulty ignition switch, alarm or immobiliser will cause this fault

Carrying out the above tests may show that there is no ignition supply to the ignition coil during cranking

You/me/we/all of us should only be interested in what the ignition coil supply voltages are (forget the negative side of the coil, at least for the time being, may not even need checking), once the above voltages are known can then delve deeper

Sorry for any confusion caused

[CAPP0]

From memory, without going and checking up, with ignition on I believe there should be a full 12v at the coil +ve?

You could run a 12v supply to the coil +ve and try starting?

[rdl001]

So,

When I test between (+ coil terminal) to (engine ground) I see:
Ignition on, 13.2 volts
Cranking, 9 volts

When I test between (+ coil terminal) and (- coil terminal) I see:
Ignition on, 0 volts
Cranking, 3 volts

Does this mean that the new ignition module I fitted is not getting to earth?

[Penelope Stopit]

OK then, best answer this first

rdl001 said:

When I test between (+ coil terminal) and (- coil terminal) I see:
Ignition on, 0 volts
Cranking, 3 volts

Does this mean that the new ignition module I fitted is not getting to earth?

The module switches a negative to the coil every time a lobe/tooth (that toothed ring that was found to be loose) passes the sensor

Hence 0 volts with ignition on is correct and 3 volts is only an indication of the switching taking place, the meter can't read and display the voltage quick enough to show 9 volts, 0 volts, 9 volts, 0 volts, 9 volts 0 volts and so on

This is why testing for voltage across the coil + & - is of little help

Moving on

rdl001 said:

When I test between (+ coil terminal) to (engine ground) I see:
Ignition on, 13.2 volts
Cranking, 9 volts

If your battery is a standard 12 volt lead acid type, the maximum measured voltage at a fully charged battery should be 12.6 to 12.65 on a warm day

You seeing 13.2 volts at the coil with ignition on means one of two things

Multimeter is faulty

or

Voltage misread/incorrectly posted????????? Was it possibly 12.3 volts????????????

If the multimeter did show 13.2 volts It's over-reading by approximately 1 volt (It is cold right now in the UK isn't it? lower the temp = lower the voltage)

Which means

9 volts measured during cranking with an over-reading multimeter could be as low as 8 to 8.5 volts

8 to 8.5 volts at the coil during cranking will very likely mean that the ignition module supply is of the same voltage (depends how it's been wired but very likely from same supply as that at the coil)

8 to 8.5 volts could easily be causing the problem

Are you able to recheck those voltages and perhaps get hold of another multimeter

There are two more readings that will help.....What is the voltage at the battery terminals when

Ignition is on

When cranking

---

Going by the voltages you have posted, no harm will be done by following the below suggestion

Please do recheck and post voltages as mentioned above even if the below suggestion fires her up

CAPP0 said:

From memory, without going and checking up, with ignition on I believe there should be a full 12v at the coil +ve?

You could run a 12v supply to the coil +ve and try starting?

Run a cable from the battery positive post to the coil positive and test

Edited by Penelope Stopit on Wednesday 4th December 23:05

[Belle427]

You can jump it off the back of the alternator just for test purposes, makes it easier being closer.

[Penelope Stopit]

Belle427 said:

You can jump it off the back of the alternator just for test purposes, makes it easier being closer.

Didn't want to mention any other locations for a positive jumper cable

Want it to be a positive directly from the battery if possible

There's 24 Hour intervals between posts here, imagine if there is a volt-drop somewhere and it is also at the alternator positive

In 24 hours time could be posting "Are you sure the alternator positive is good?"

24 Hours later get a yes or no.................................

---

That said.......................Yes good idea, if the alternator positive jumped to the coil positive starts her, problem is proven.

But if she doesn't start, connect jumper cable to battery positive

Will still need those above mentioned voltages though

Edited by Penelope Stopit on Thursday 5th December 08:16

[Belle427]

Penelope Stopit said:

Belle427 said:

You can jump it off the back of the alternator just for test purposes, makes it easier being closer.

Didn't want to mention any other locations for a positive jumper cable

Want it to be a positive directly from the battery if possible

There's 24 Hour intervals between posts here, imagine if there is a volt-drop somewhere and it is also at the alternator positive

In 24 hours time could be posting "Are you sure the alternator positive is good?"

24 Hours later get a yes or no.................................

---

That said.......................Yes good idea, if the alternator positive jumped to the coil positive starts her, problem is proven.

But if she doesn't start, connect jumper cable to battery positive

Will still need those above mentioned voltages though

Edited by Penelope Stopit on Thursday 5th December 08:16

Yes your quite right.
In my head if it starts when releasing the key from crank it could be a voltage drop issue due to the starter disengaging.
Just a guess, I’m not an auto electrician!

[rdl001]

Hi Pen and Belle,

I was testing the voltages last night with my trickle charger still plugged in, so this may explain my high voltages.

on retest,

When I test between (+ coil terminal) to (engine ground) I see:
Ignition on, 12.3 volts
Cranking, 8 volts

When I test between (+ coil terminal) and (- coil terminal) I see:
Ignition on, 0 volts
Cranking, 1.7 volts

When I test between (+ battery terminal) and (- battery terminal) I see:
Ignition on, 12.3 volts
Cranking, 8.1 volts

Does that make more sense?