Help please mk2

Can a coil fail instantly while the warmed up car is idling , and with the ignition on I should be able to manually open the points and get a spark yes?

It could if it 300 years old with heat cycles…
Replacement chinese condensors that say lucas are terrible as well and will do the same.

It’s a new one from Martin jay

Morning Ken

In order to eliminate some stuff, I’d hot wire the ignition side of the coil rather than expecting ‘the car’ to provide that. There could be something wrong before the coil, rather than (or as well as) after the coil.

But be sure not to leave the coil powered up for long periods of time as it will get very hot & they have been known to explode.

Morning Bob, I’m not familiar with that procedure , I’ll get my protective bomb proof suit on while you explain it

What you do is eliminate all the wiring & switching that comes before the coil by running a wire from the live (not the earthed) battery terminal direct to the SW terminal on the coil. Be aware that the coil will be permanently live if you do this, and not controlled by the ignition switch and if your engine starts you will have to pull this wire off to stop it. Also be aware that if this works it means that you have something dodgy behind the dashboard and you would be connecting the full force of the battery to it which it might not like so disconnect the wiring that is currently connected to the switch side of your coil so you eliminate everything from your circuit except the coil and the distributor. And connect your wire to the coil first and then the battery as you don’t want a live wire flopping around looking for an earth.

Your coil will probably be marked SW and CB (switch and contact breaker) or it might be marked + and - and in this case this will tie in with the polarity of your particular car. Mine is -ive earth so if my coil is marked + and - it will be the - terminal that goes to the distributor but as yours is earlier it will probably be +ive earth so the + terminal will probably go to the distributor. I have seen coils wired the wrong way round and if you’ve changed the coil and you’re not aware of this that might be the problem, although probably not as your engine just stopped while it was already running.

If your coil is marked + & - then the marking on the coil that the wire runs to the distributor from will be the same as the marking on the battery that the cable runs to the body from.

After disconnecting the wire from the ignition switch that is already on the coil you will end up with a very simple circuit that will eliminate every other possible cause. Your electricity will go through the wire that runs from the live side of the battery to the correct connection on the coil, through the coil, through the wire that connects the coil to the distributor, through the points and to earth.

p.s. if that doesn’t solve it, and you’re still scratching around, your ignition system will function without a condenser (so you can remove that to eliminate it) as the purpose of the condenser is to eliminate as far as possible any sparking at the points and thereby prolong their life so you don’t actually need a condenser to get a spark at the plugs. But of course you should not run the car without one for any longer that simply to establish it as being faulty.

You could also try running a wire from the coil to the distributor (or at least testing the existing one’s continuity) as wires can sometimes simply go open circuit or high resistance for various reasons.

And finally turn the engine with the distributor cap off to eliminate a problem with the mechanical drive to the distributor!

Wow ! Thanks for that Bob , mine is neg earth ,but I get the picture, I’ll give it a go.

You kids are funny…Robert is on top of this…
,Make it even easier…
You have points…
Just pull off the coil lead wire should be white…Put a test light to that wire with the key on then you know you have KEY power to the coil.
Once you see the light , you know the ignition key side is ok.
Does the car crank?
Is the fuel pump working?
And so on…I like the exploding coils…more drama than GTJOEY explaining his love life 50 years ago :slight_smile:

Yes, Ok, I agree but how much? How do you know that’s enough?

A bad joint in the circuitry leading to the coil will fail when a large(ish) amount of current is drawn but will test perfect by using a test light or multimeter.

Just eliminate all that stuff altogether and if this is where the fault lies at least you’re not looking in the wrong place.

Yes it eliminates the primary circuit.

Think Petronix or 123Ignition. Search this forum for lots of information on these electronic replacements.

The tips given above are very good but its nice to eliminate points and condensers and wobbly dizzy shafts with a new distributor.


Hi guys, welcome to the latest installment of the mk2 saga , now don’t groan, wait till I get this exploding coil suit off and I will continue. Yes I have key power to the coil, and the car does crank, and the pump is working . But great news, a breakthrough , I hope . The short earth lead that connects the base plate to the side of the dizzy came off in my hand , suggesting that wasn’t good in the first place. I will solder a new one on tomorrow and hopefully that will do the trick.

Hi ,it’s great to be associated with kids, I’m probably older than you , but keep calling me kid, it’s great

I’m not sure what wire you are referring to but there is a short wire from a nylon terminal on the side of the distributor body that goes to the spring eye of the points which is held in place with a small nut. These are made to be quite flexible as the base plate for the points does move with vacuum advance movement. These wires can break inside their black sleeve and cause an ignition failure. Can be intermittent depending on how the vac advance is positioned at any given time.

Hi john, this wire is about 2ins long and is soldered to the baseplate and connected with a screw to the side of the dizzy in a small recess.i do also have an extension to the CB lead which is a continuation fixed through the side of the dizzy ,this together with the capacitor lead goes on the spring eye of the points.

Great to hear…hope it does it…
The long run…123

Sounds promising - that would explain it nicely.

I also quite liked being called a kid, although I will soon receive my (delayed) state pension!

And not only are we still kids, we are Welsh as well! What more could you want! :joy: :joy: :joy:

Hi Bob , no result I’m afraid , a big let down ! Fitted a new super coil as well . I must be missing something obvious .

Disconnect the coil and crank the engine for a minute with the choke on. Your plugs should be soaking wet. Unless you have already eliminated petrol, of course!

Or perhaps it’s the ht lead from the coil to the distributor? That would stop all sparks while everything before it was working Ok. Another trick maybe worth trying is to crank the engine while it’s dark - you will often see sparks where they shouldn’t be, and you won’t see them if it’s light. That worked for me once.