16 replies to this topic

[Henry8601]

After taking my mini for a rolling road session one of the outcomes was that the spark was pretty pathetic on my 1964 mk1 850. Slark Race Engineering advised me to upgrade to electronic ignition, and the car has been converted to negative earth (dynamo flashed, coil wiring changed and confirmed, battery wiring swapped). I fitted a high power distributor from Powerspark, and a high energy coil:

 

http://www.simonbbc....x-red-rotor-arm

 

http://www.simonbbc....c-ignition-coil

 

They were both really easy to fit, and I confirmed that I had +12v at the positive side of the coil. I set it up with an ht lead to a spare spark plug against the head to test the spark. It had a nice fat spark for the first 2 pulses, then nothing, then some small sparks. I thought I had a bad earth, so I tried properly clamping the spark plug in place. Still the same problem, and I noticed that the spark was jumping about on the plug a lot. I tried some different ht leads, different (new) spark plugs, and tried different positions on the distributor cap, but still the same result with the spark randomly being big, small, or non-existent. 

 

Has anyone experienced this before, or have any ideas as to what is happening and how I fix this?

[jaydee]

Dont try to fix something thats not yet broken what are you trying to diagnose?

[Henry8601]

Originally it had a really weak spark and a large degree of scatter due to a worn distributor, and Slark Race Engineeing advised an upgrade to electronic ignition. 

 

After the upgrade the spark appears to be really erratic (as per title) and I wanted advice on whether this is (for example)

 

a) symptoms of a dead coil

b) symptoms of a dead electronic ignition unit

c) some other thing that forum users have found when they did XYZ

d) normal

 

As far as I can tell it isn't working properly i.e. broken, so I'm asking for advice on what to do next.

Edited by Henry8601, 11 August 2013 - 11:44 PM.

[jaydee]

Is it erratic based on running the engine or just by looking at a little spark jumping through a 25 thou gap? If so what are the sympthoms (ie missfire, pinking etc..)?

What are the manifacturer reccomandations for leads, sparks and plug gap?

[DILLIGAF]

Check the trigger ring is located properly, there another thread about this problem with the same kit.........

[robminibcy]

have you actually tried running it yet? If not set the gap on the spark plugs correctly and give it a try!

Edited by robminibcy, 12 August 2013 - 12:36 AM.

[Captain Mainwaring]

After taking my mini for a rolling road session one of the outcomes was that the spark was pretty pathetic on my 1964 mk1 850. Slark Race Engineering advised me to upgrade to electronic ignition, and the car has been converted to negative earth (dynamo flashed, coil wiring changed and confirmed, battery wiring swapped). I fitted a high power distributor from Powerspark, and a high energy coil:

 

http://www.simonbbc....x-red-rotor-arm

 

http://www.simonbbc....c-ignition-coil

 

They were both really easy to fit, and I confirmed that I had +12v at the positive side of the coil. I set it up with an ht lead to a spare spark plug against the head to test the spark. It had a nice fat spark for the first 2 pulses, then nothing, then some small sparks. I thought I had a bad earth, so I tried properly clamping the spark plug in place. Still the same problem, and I noticed that the spark was jumping about on the plug a lot. I tried some different ht leads, different (new) spark plugs, and tried different positions on the distributor cap, but still the same result with the spark randomly being big, small, or non-existent. 

 

Has anyone experienced this before, or have any ideas as to what is happening and how I fix this?

 

Check your cranking voltage. The initiator ring shouldn't cause a fat spark, weak spark etc, if you get a spark it should be consistent at least even if not periodic.
My guess is that the Chinese only every tested these units with a lab power supply and never took into account the 2.5 miles of bell wire between the mini battery and starter.

[Henry8601]

The problems are when turning the engine over and observing the spark - I haven't yet tried running the engine.

 

Check the trigger ring is located properly, there another thread about this problem with the same kit.........

 

Thanks for a few of the pointers, but I have tried searching and can't find it, can you provide a link please?

 

For reference I have spoken to Powerspark who were really helpful. They said it sounds like the symptoms you get when a ballast resistor system is fitted, but I'm certain I don't have one. Instead they have sent out a new coil as that is likely to be the culprit, and they said I also need to check the coil voltage while cranking (as you also say above) and check for 5 Kohm resistance in the HT leads.

 

I will report back once I have had  a chance to fit the new coil.

[Tamworthbay]

Here is one of the threads:

http://www.theminifo...tronic ignition

[Captain Mainwaring]

I think Powerspark need to investigate what is happening to their modules when fed with reduced voltage - the fact that they suggest a ballast resistor is in circuit suggests they may already suspect.

[KernowCooper]

If you have 12v at the coil what does the car drive like? and if you fit a sports coil and the leads have a high resistance then you wont get the benefit, whats the ohms readings on the ignition leads? in the FAQs under electrical there is a article about Testing Ignition Leads

[Henry8601]

I fitted the new coil today, but no change.

 

Next step was to test the HT leads, and they are all 5 kOhm, so spot on.

Next test I did was to check the voltage at the coil while cranking, and my healthy 12.5v at the coil while at rest dropped to 9.5v! I guess this must be below the value the electronic ignition needs to operate?

 

So that's potentially the problem. Any ideas on the solution?

Would fitting a decent new battery help:http://www.carbatter...battery075.html? The current battery is of unknown origin and age, but it has always held its charged, and always started the car with no problems (hot, cold, after sitting for weeks etc.), so never suspected it. Alternatively could it be high resistance in the cables? The huge drop in voltage looks like it might be the battery breaking down under load, what do you guys think?

Edited by Henry8601, 13 August 2013 - 08:34 PM.

[KernowCooper]

Check the voltage at the battery when cranking and if you getting the 9v'ish reading on the battery terminals then suspect the battery, I have also seen defective starter motors do very similar.

 

If you battery is showing around 12v you need to look at volt drop on the cars wiring and this will check for dirty connections causing a high resistance and voltage drop, you need to carry out a voltage drop test on the cars battery + and negative to the car body. including all feed wiring from the coil to fuse box even across the fusebox terminals itself.

 

You select volts to test volt drop on your meter and a digital one is essential, if your unsure how its done read the topic here http://www.theminifo...ring-volt-drop/

[DILLIGAF]

This the one I mean't:

http://www.theminifo.../?hl= accuspark

[Captain Mainwaring]

Check the voltage at the battery when cranking and if you getting the 9v'ish reading on the battery terminals then suspect the battery, I have also seen defective starter motors do very similar.

 

If you battery is showing around 12v you need to look at volt drop on the cars wiring and this will check for dirty connections causing a high resistance and voltage drop, you need to carry out a voltage drop test on the cars battery + and negative to the car body. including all feed wiring from the coil to fuse box even across the fusebox terminals itself.

 

You select volts to test volt drop on your meter and a digital one is essential, if your unsure how its done read the topic here http://www.theminifo...ring-volt-drop/

 

I think if you ask everyone here to do the same test you won't get far differing results. As a bit of fun I checked a big diesel yesterday (3.2 litre) with a monster battery in fresh charged condition - cranking volts dropped down to 9.75-10.2V - and that was at the battery terminals.

I forget what pub technician said that the ballast system used on minis was a load of rubbish and completely unnecessary but perhaps BL weren't so stupid after all.

 

 

With that in mind I think that the 9 ish volt condition being seen here is fairly typical and that the electronic ignition modules just aren't capable of dealing with it. 

I'll get my power analyzer back today and do a more detailed test as the response time of the meter is no way near fast enough but I also expect that if the meter is logging 9V that there are plenty of troughs of lower voltage.

 

To the OP, a clean up of all terminals and a new battery may help....but it isn't the ultimate solution to the problem.

I'm afraid it's yet another case where a £15 module made somewhere the BBC is banned isn't designed to suit operating conditions.