Ignition problem?

[steamy]

Limped back home after a fault developed in what I think is the ignition system. No power lots of bangs and pops from exhaust and ammeter needle swinging from 0 to +25amps. Bonnet up but nothing obvious. Started engine and seemed fine so drove again for about 10 minutes then fault reappeared. Got home and again after cooling down everything fine but not ventured out! Car is fitted with a Lumenition CEK150  Optotronic system and about 3 years ago the coil broke down when hot and I replaced it as Lumenition said it was a known problem with a particular batch. 

Can anybody with more knowledge than me confirm or otherwise my thoughts.

If it is the coil again then not much faith in their system so any thoughts on a better way forward or back to standard points etc

 

Many thanks for any thoughts and advice

Regards

Ian

[RobH]

Well that certainly sounds like ignition Ian but the swinging of the ammeter needle puzzles me a bit.  Could that just have been due to vibration?  I wonder whether you have a fault in the ignition switch or wiring (including the ammeter connections) which is cutting out power to the ignition -  or perhaps the supply wire to the coil has a bad connection?

I think my first check would be to ensure you have power where it ought to be and that the connections between the Lumenition and coil are OK. 

After that, if the fault is heat-related it may be the coil or the Lumention system itself. Really the only way to go then is to replace the coil again.  If the fault clears you know it was that - if it doesn't, well you then have a spare coil...... 

 

 

[steamy]

Hi Rob,

Thanks for your reply.

I too was puzzled by the ammeter but pretty sure not vibration. If short inside coil then this could make the alternator charge more? but not sure why it would swing unless as the revs were all over the place that could do it? As fault goes away when left to 'cool' a bit I agree with you re try new coil first. 

As I cant replicate fault without driving then it will be an anxious drive to prove it.

 

Thanks

Ian

[RobH]

No Ian - a fault with the coil won't affect charging which is what makes me suspect the wiring/connections.  I would inspect that thoroughly before changing the coil.  I would also check the earthing from the engine to the chassis. 

 

 

 

Edited August 29, 2021 by RobH

[steamy]

Rob, OK thanks. Will do some checking.

 

Ian

[ctc77965o]

maybe you have an electrical issue creating wild swings in voltage...that might explain the ammeter movements and electronic ignitions get rather grumpy when you take away their volts  ??

[steamy]

Hi Dave,

I am going to give it a though check over tomorrow and see what I can find.

Strange that it appears to be effected by heat though.

 

Thanks for your input

 

Ian

[ctc77965o]

If the main 12V supply was randomly going on-off due to a bad connection, then the coil would fire at that random moment the 12v supply drops..that would create a misfire if the 12V interruption happened regularly......

[steamy]

Dave,

That makes sense. So far have proven not coil or ignition unit so could be what you say or alternator.

Onwards and upwards.....

 

Thanks

Ian

[RobH]

If the car has an alternator it must have been converted, as originally it would have a dynamo.  It might be an idea to  check how the connections were altered when the control box was taken out of circuit. There will be a common point where the alternator output feeds the ammeter and the ignition switch. 

[steamy]

Rob,

Yes I did conversion about 5 years ago. I will check the 'hidden' connections in old regulator box as well

Thanks

Ian

[trchris]

Hi Ian

I had a brief intermittent electrical fault last year once or twice no electrics last time it happened traced fault to quick release battery joint 

Chris  

[keith1948]

Could be plug leads shorting onto inside of bonnet or dipstick. Happened to a friend of mine. Car worked fine when bonnet was open but not when it was closed. As the car turned corners I think the engine was moving slightly from side to side and was just enough to move the plug leads and cause the fault.

Keith

[Nigel C]

I've had an intermittent ignition fault for 4 months, engine just stops dead. Cant induce it just happens. Took a live feed straight from the battery to the coil (pain in a**e for a few weeks) and it cured it.

Made a new feed wire from the ignition feed/fuse box to the coil, stopped dead again in less than three days. That eliminated a loom fault.

Then kept loosing Overdrive feed...and then fans...... Wiggled said fuse box and everything came back!

Thrown 6 year old fuse box away (I have two, 4 fuse type) and found genuine 60 year old item, cleaned up and fitted....all good so far  so looking for another old one!

[RobH]

...but as standard the ignition circuit isn't fused Nigel.......perhaps that is why?!  

[RogerH]

Hi Ian,

 this may be a 'red herring' but about 6 years ago on a Scottish tour my engine would simply cut out. I would waggle a few wires and off we went

This lasted for about 3 days. Thankfully it didn't cause too much inconvenience with ferries and high passes but  coming into Pitlochry if failed for the last time.

I checked through the ignition  system and all was good. In desperation I took the dizzy electrics to pieces.

I have a lumenition module that simple replaces the CB's - this was swapped for a known good one - no change.

I came to the little flexible wire that connects the to the CB and the coil.   It is soldered on its conductor and there is a gripper that holds the insulation.

The solder connection had broken down and was occasionally going open circuit - until it was permanently O/C. The gripper held it precisely in this state.

A quick dab with a soldering iron and all sorted.

Check EVERY connection and waggle it.

 

Roger

[steamy]

Thank you everybody for your inputs and experiences.

The alternator was the problem! It must have been 'breaking down' when hot possibly one of the diodes? This presumably as Dave said caused swings in voltage or even power on/off causing the Lumenition ign unit not knowing whether it was counter bored or punched! I have a home made heat shield fitted but still gave a problem.

I carry a spare coil and ignition unit also cb points and plate but not a big alternator.

Been putting off fitting the Denso alternator I've got as got to fabricate a bracket but definitely on my list of to do's for winter.

 

Thanks

Regards

Ian

[RogerH]

Well found.

 

Roger

[Nigel C]

1 hour ago, RobH said:

...but as standard the ignition circuit isn't fused Nigel.......perhaps that is why?!  

pleased to hear/read it, well done.  

Standard? what's that  Have you seen a fibreglass car go up everything's fused!!

[RobH]

20 minutes ago, steamy said:

The alternator was the problem! It must have been 'breaking down' when hot possibly one of the diodes?

Well that is rather odd.  The battery should act to stabilise the voltage even if the alternator was turning on and off - the supply to the ignition should never have gone below battery voltage.

 

 

[RobH]

3 minutes ago, Nigel C said:

Standard? what's that  Have you seen a fibreglass car go up everything's fused!!

 OK - better safe at the side of the road than sorry with the FB in attendance I suppose. 

[Nigel C]

good point, well raised......

[BlueTR3A-5EKT]

If you wobble/jiggle the ignition key up and down, side to side in the ignition key hole, when the engine is running, does the problem happen?

if so…..Ignition switch making and breaking.  
Fit another ignition switch.

 

Very MG problem that when you have lots of gubbins on the car keys key ring, the weight damages the lock/switch mechanism.

Peter W

[Lebro]

How did you get a photo of my keyring ? 

[steamy]

Think problem is sorted but didn't try the key/ignition switch trick Peter. 

Thanks

Ian