14 replies to this topic

[EpicFruit]

My Mini has been experiencing some starting issues recently, the engine will crank but will not fire. I suspected it to be an electrical fault, so I did a bit of measuring with a voltmeter, and it appears that the ignition coil is getting roughly 8.4 Volts. It was measured from the positive terminal of the ignition coil to the engine block, and I got the same voltage across the coil terminals. The resistance of the coil itself was 3.6 Ohms across the terminals, which I think might be a bit high. Nevertheless, I think it's producing a weak spark. 

 

When I disconnected the ignition coil suppressor and cranked the car again, it started, although a bit reluctantly. To make sure this wasn't random, I reconnected the suppressor, got no start, then disconnected it again and got another reluctant start. How is it possible that the ignition coil suppressor is able to make such a difference? Is my ignition system so weak that it's being pushed over the limit by a capacitor?

[sonikk4]

Have you checked the engine earths?? Are you running points or electronic ignition?? If points are they gapped correctly, the nylon pad lubricated and the points correctly located on the dizzy base plate??

[dklawson]

Were the wires attached to the coil when you measured its resistance?  If so, mark and remove the wires, then repeat your measurements.

 

What colors are the wires connected to each coil terminal?

Does the distributor have points or an electronic ignition?

 

Points can close up over time making starting difficult.  Condensers can fail making sparks weaker.  Let us know what your car has for an ignition system.

[carbon]

+1 for above questions, would be helpful to know year etc.

 

And does it have ballast / resistor wire fitted? This could explain the low voltage at coil.

[EpicFruit]

Apologies for the lack of information. It is a points ignition, on a 1990 Mini with a 1293 engine. There are two wires connected to the positive terminal of the coil, one is a pink and white resistor wire from the loom, and the other is a black wire from the capacitor on the coil bracket. The negative terminal of the coil has one black wire. I have taken the distributor cap off for a visual inspection, but don't really know what to look for other than signs of moisture, excessively worn parts, etc., I will take a picture of it tomorrow and update this thread. 

 

When I tried cranking it today, I was no longer able to get a start by disconnecting the coil suppressor. However, the car would "cough" the moment I stopped cranking. Perhaps it was able to produce a spark just as the starter stopped drawing power?

 

Lastly, shouldn't there be another wire going to the coil with a full 12V in systems that have a ballast or resistor wire?

Edited by EpicFruit, 23 April 2016 - 07:45 PM.

[iDustx]

Hi epicfruit , I've recently posted a topic about my car not firing up also, there could be some information on there that can help you, also there is a video, does your car sound like mine when it tries to fire?

Edit: have you checked your spark plugs and leads? Check the ends of the Sparks for deposits

Edited by iDustx, 23 April 2016 - 10:06 PM.

[iDustx]

I will dig up a wiring diagram for you from the Haynes manual if you need it

[dklawson]

Refer to my last post.  Mark and remove the wires from the coil and measure its resistance that way.  If it is still 3.6 Ohms, you have the wrong coil installed and the spark will be weak.  

 

With a pinkish wire on coil (+), your car has ballast ignition wiring and it needs a ballast coil rated between 1 and 2 Ohms.  If you use a standard coil on ballast wiring, the coil operates at a lower voltage than designed for and the spark will be weak.  That will make the engine hard to start.

 

You are correct, with ballast wiring you should also have a white/yellow wire from coil (+) to a 4th terminal on the starter solenoid.  That is the ballast bypass wire.  It delivers higher voltage to the coil (for easier starting) while the engine is turning on the starter motor.

[EpicFruit]

Refer to my last post.  Mark and remove the wires from the coil and measure its resistance that way.  If it is still 3.6 Ohms, you have the wrong coil installed and the spark will be weak.  

 

With a pinkish wire on coil (+), your car has ballast ignition wiring and it needs a ballast coil rated between 1 and 2 Ohms.  If you use a standard coil on ballast wiring, the coil operates at a lower voltage than designed for and the spark will be weak.  That will make the engine hard to start.

 

You are correct, with ballast wiring you should also have a white/yellow wire from coil (+) to a 4th terminal on the starter solenoid.  That is the ballast bypass wire.  It delivers higher voltage to the coil (for easier starting) while the engine is turning on the starter motor.

 

I removed the wires from the coil and measured the resistance across the terminals again, and still got 3.6 Ohms. It does seem like I have a non-ballast coil, but then I measured the voltage from the white/pink resistor wire, and got 12.6 Volts. However, when I connected it back to the positive terminal on the coil, it dropped to 8.6 Volts.

 

Here's what the distributor looks like at the moment:

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[carbon]

Sounds like the ballast resistance wire is working exactly as it should. When volts applied but no current is flowing you will see full battery voltage. Once you connect the coil and draw several amps then the resistance causes the drop in voltage.

[dklawson]

+1 to Carbon's post.  For the voltage drop to occur there must be current flowing.  Your measurement of 12+ volts on the pink wire with no load is correct.  The 8+ volts with the coil wires attached will be "correct" while the points are closed (or electronic ignition module is conducting).

 

Start making one off two changes.  Either run a white bypass wire to coil (+) from the fuse box so you can use your existing coil... or buy a ballast coil.  Wire is cheaper than coils.  Either solution will give you a hotter spark than you have now. 

[EpicFruit]

Thanks guys, I'll probably buy a ballast coil and run another wire from the starter solenoid to the positive terminal. The (wrong) coil on the car right now was working for a little while after I got the car, but it seems to be getting worse and worse. Me and some friends bump started the car today and it was misfiring all over the place, with a very strong smell of unburnt fuel from the exhaust. The coil may have taken on some moisture while we drove through the rain on the way home, especially without a front grille attached...

 

According to the Haynes manual, the car should have had a Lucas GCL143 coil from the factory. But the car should also have had an electronic distributor from the factory, so would it cause any issues if I run a GCL143 coil with the points distributor in the car? And if I remember correctly, the GCL143 coil was factory fitted to 1275 engines, so would it be safe to say that it will also work with my 1293?

[dklawson]

The reason your coil seems to be running weak and tired is because it is not running with the correct voltage.  

 

You can always put a ballast coil on if you want.  However, I encourage you to first try running a white wire from the fuse box to the coil (+) terminal and try that for a while.  If it works, run that coil indefinitely.  The new wire is cheap, quickly installed, and will allow your existing coil to work the way it was intended.  If you are not happy with the coil wired that way, by all means buy a new ballast coil and add the bypass wire (white/yellow) from the starter solenoid to coil (+).

 

Lucas coils have a rather poor reputation these days.  Visit the Mini Spares web site and see what they are selling as an alternative to the Lucas coil.  

 

Footnote:  If you do a search here you will find a nearly infinite number of threads on replacing the ballast coil with a standard coil and eliminating the use of the pink wire.  Most feel it is a liability as the pink wire has a reputation for overheating and melting inside the loom.  By rewiring your existing standard coil you are in a position to cheaply and easily convert your car's ignition wiring and improve the car's long term reliability.

[KernowCooper]

I'd run a 12v feed wire even a temporary one would serve to do the tests Doug mentioned above, and then if it runs ok then wire in a new White ignition controlled feed from the no1 fuse take off and disconnect the white currently there which connects to the White/yellow inside the loom where the resistor is, why I advise running the 12v system is because the resistor burns out eventually as the wiring gets older and takes the loom with it.

[EpicFruit]

Thanks everyone! I took Doug's advice and ran a new wire straight from the fuse box to the coil, and she started right up on the first crank. I drove around for a bit and opened up the throttle here and there, and she ran beautifully, even had the occasional crackle from the exhaust. I really could not have been happier to see her running like a champ after all the trouble she's had recently. Thanks again!

 

I may eventually look into an electronic system for the sake of maintenance, would it be better to go with a fully electronic dizzy or just a drop in conversion kit? I was also thinking of getting the Lumenition ballast coil from minispares. I'll definitely run that with an external ballast resistor if I ever do so, the idea of that resistor wire melting in the loom does not sound like fun.