Weird starting issue

[caduceus]

My Chim developed a starting issue a few weeks ago. After some investigation it turned out the spark from the kind lead was weak. So I ordered a new coil which I fitted today. Turned the key and it spun up but didn't start on the key. As I let go of the key (in the ignition, to back to position 2) it fired up and ran fine.
I switched it off and tried again to see if it would fire up the conventional way, and its not firing at all now.

Any ideas chaps?

Thanks in advance
Cad

[TwinKam]

Do you have a ballasted coil?

[caduceus]

TwinKam said:

Do you have a ballasted coil?

How do I find that out?

[TwinKam]

Check to see what voltage you have at the coil +ve when key is in run position, and also whilst cranking.

[blitzracing]

It would be the wrong way around, if you put a ballasted coil in the system, it would produce a good spark but over heat as its not a ballasted system so it would get 12v when it expects about 9. It does sound suspicious that you are not getting a high enough voltage on the coil when cranking, so check the +ve connection on the coil as you run the starter. It should not be much below the battery voltage- certainly not below about 10 volts worse case.

[Penelope Stopit]

As above, first check with original coil wired up just in case the new coil is of the incorrect voltage

The coil supply voltage can only be measured correctly by having the coil load on/in the circuit

A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit

You need to remove all cables from the ignition coil negative terminal

Use a jump lead to connect the coil negative to battery negative or a known good earth

Now switch the ignition on and measure the voltage at the coil positive

Don't leave the ignition on for too long as the coil could overheat, 10 to 15 seconds isn't a problem

You will have then measured the supply voltage to the coil while it is under coil load (coil is drawing current)

[Loubaruch]

Check the ignition switch. I had the same problem a while back on a Land Rover and found that while the ignition feed was live in the crank position when turned back to normal running the ignition feed vanished.

[caduceus]

Many thanks for the replies gentlemen. I'll dig out the voltage tester I've forgotten how to use tomorrow and attempt the above.
Much appreciated

Cad

[TwinKam]

A non ballasted coil has only one supply (12v). A fault in that supply will mean that the engine will not fire.
A ballasted coil has two supplies; 9v when running, and 12v when cranking. If there is a fault in the 12v supply wiring, there will be no supply during cranking, but it may 'catch' and run on the 9v supply when the key is released... if the engine has sufficient momentum to make compression.

[rdl001]

I had exactly the same issue and it turned out to be a faulty ignition module.
See thread: https://www.pistonheads.com/gassing/topic.asp?h=0&...

[Penelope Stopit]

TwinKam said:

A non ballasted coil has only one supply (12v). A fault in that supply will mean that the engine will not fire.
A ballasted coil has two supplies; 9v when running, and 12v when cranking. If there is a fault in the 12v supply wiring, there will be no supply during cranking, but it may 'catch' and run on the 9v supply when the key is released... if the engine has sufficient momentum to make compression.

Good morning my friend

Not meaning to come across as a proper bh or anything like that but........

Ignition switches that switch off the coil ignition supply when in the crank position are hard to find, terminal 15 (ignition) and terminal 51 (crank) are more often than not both live when in the crank position

Should the 12 volt supply from the starter solenoid to ignition coil fail there will still be a 9 volt supply present at the coil from the ballast resistor

If it was the case that the ballast resistor ignition supply was switched off during cranking there would be 2 big problems, one big problem being that all vehicle ignition driven components would be reverse supplied from the starter solenoid 12 volt ballast bypass terminal through the ballast resistor when cranking

The second big problem being that the engine would momentarily die when the key is released from the crank position back to the ignition position

Appreciate that you're not telling lies or anything of the sort, the following is very fitting for this topic

What are the chances of a music group being named after a starter motor crank terminal?

Terminal 51 - Web Of Lies


Stay safe all

[TwinKam]

Only mentioned it because I've encountered this fault in the past, real life experience and all that.
But I'm only too happy to defer to your clearly vastly superior knowledge on all things, crack on Penny.

[caduceus]

TwinKam said:

A non ballasted coil has only one supply (12v). A fault in that supply will mean that the engine will not fire.
A ballasted coil has two supplies; 9v when running, and 12v when cranking. If there is a fault in the 12v supply wiring, there will be no supply during cranking, but it may 'catch' and run on the 9v supply when the key is released... if the engine has sufficient momentum to make compression.

My coil has 4 wires going to it...2 live 2 neg. So I assume mine is ballasted.
I must admit, what you have written above does sound like the issue I am having. Going out there in a minute to dig out the tester and get testing.

[caduceus]

Ok. I've just checked the voltage at the coil+. It's 10v with the ignition on, but drops to 7 volts whilst cranking. This is the top black connector that does to the +'ve (one of the 2 connectors from the top loom covered in plastic shrouding).

[Penelope Stopit]

TwinKam said:

A non ballasted coil has only one supply (12v). A fault in that supply will mean that the engine will not fire.
A ballasted coil has two supplies; 9v when running, and 12v when cranking. If there is a fault in the 12v supply wiring, there will be no supply during cranking, but it may 'catch' and run on the 9v supply when the key is released... if the engine has sufficient momentum to make compression.

Good morning my friend

Not meaning to come across as a proper bh or anything like that but........

Ignition switches that switch off the coil ignition supply when in the crank position are hard to find, terminal 15 (ignition) and terminal 51 (crank) are more often than not both live when in the crank position

Should the 12 volt supply from the starter solenoid to ignition coil fail there will still be a 9 volt supply present at the coil from the ballast resistor

If it was the case that the ballast resistor ignition supply was switched off during cranking there would be 2 big problems, one big problem being that all vehicle ignition driven components would be reverse supplied from the starter solenoid 12 volt ballast bypass terminal through the ballast resistor when cranking

The second big problem being that the engine would momentarily die when the key is released from the crank position back to the ignition position

Appreciate that you're not telling lies or anything of the sort, the following is very fitting for this topic

What are the chances of a music group being named after a starter motor crank terminal?

Terminal 51 - Web Of Lies


Stay safe all

TwinKam said:

Only mentioned it because I've encountered this fault in the past, real life experience and all that.
But I'm only too happy to defer to your clearly vastly superior knowledge on all things, crack on Penny.

No need to get nasty

TwinKam said:

If there is a fault in the 12v supply wiring, there will be no supply during cranking, but it may 'catch' and run on the 9v supply when the key is released

Your above comment reads like you think a fully functioning ignition circuit with ballast resistor has no supply to the ballast resistor during cranking

An ignition circuit with ballast resistor does have a supply to the ballast resistor during cranking

If the 12 volt supply to the coil from the starter solenoid goes open circuit as you mention

TwinKam said:

If there is a fault in the 12v supply wiring, there will be no supply during cranking

the 9 volt supply from the ballast resistor will still be present and the engine may or may not fire on that 9 volt supply depending on its temperature

Had posted a reply to you with good intentions yet you reply back with

TwinKam said:

But I'm only too happy to defer to your clearly vastly superior knowledge on all things, crack on Penny.

Think about it, wasn't called for was it?

Now if you meant that the 12 volt supply could be missing from all ignition circuits during cranking, it's a different ball game and I've misunderstood your comments

Still no need to get nasty is there?

Edited by Penelope Stopit on Wednesday 13th January 11:35

[Penelope Stopit]

caduceus said:

Ok. I've just checked the voltage at the coil+. It's 10v with the ignition on, but drops to 7 volts whilst cranking. This is the top black connector that does to the +'ve (one of the 2 connectors from the top loom covered in plastic shrouding).

Need to now do the same again but also check battery voltage with ignition on and then coil voltage with ignition on

then

Battery voltage during cranking and coil voltage during cranking

Reason being

Battery voltage will be dropping to some unknown figure during cranking and will need to know that figure

[Penelope Stopit]

As mentioned earlier, coil supply voltage can't be checked without disconnecting all negative cables from it and then connecting the coil negative terminal to a known good earth or battery negative

[caduceus]

Am I right in assuming I am sticking a probe from the meter into the +ve whilst it is unplugged from the coil to test it? Or am I supposed to be checking the +ve whilst it is plugged onto the coil terminal?
Sorry for the dopey questions but I'm a bit thick when it comes to electrical stuff

[Penelope Stopit]

Coil needs to be in the circuit and

Penelope Stopit said:

As above, first check with original coil wired up just in case the new coil is of the incorrect voltage

The coil supply voltage can only be measured correctly by having the coil load on/in the circuit

A bad supply or a supply through a ballast resistor will still measure as 12 volt when the coil load isn't on/in the circuit

You need to remove all cables from the ignition coil negative terminal

Use a jump lead to connect the coil negative to battery negative or a known good earth

Now switch the ignition on and measure the voltage at the coil positive

Don't leave the ignition on for too long as the coil could overheat, 10 to 15 seconds isn't a problem

You will have then measured the supply voltage to the coil while it is under coil load (coil is drawing current)

[Penelope Stopit]

Need battery voltage as well