16 replies to this topic

[dwealds]

Hi, I am getting so fed up with my Mini, it keeps burning ignition coils out and I've heard differing opinions from different suppliers as to whether I can run a 12volt coil with an electronic distributor?!

It has a ballasted ignition system but when running I still have 12volts on the + on the coil and from my understanding this will burn a 9volt coil out in next to no time.

So my question is can I just run a new feed from te fuse box to a 12volt coil and not ruin my electronic distributor?

[tiger99]

In a conventional system, when the points are open, you should see 12V on either coil terminal, as there is no current flowing, and so no voltage drop in the ballast resistor. Engine running, you should see less, as the points are closed part of the time, and current flows. I assume the electronic distributor simply replaces the points with a transistor switch, so the same applies.

If you short the CB (negative) side of the coil to earth on the engine block, engine not running, you should see about 6 to 8V only on the positive coil terminal, thus proving that the ballast resistor is working. If you still see 12V there is a wiring fault.

I think the ballast resistor is not in circuit, or is being bypassed. Is the connection to the starter solenoid, which provides a bypass for starting, on the correct terminal?

[dwealds]

Ok thanks, I will try shorting the coil when not running in a bit and see what reading i get then. When the engine is running I see as near as dammit 12V.
I'm not sure, the yellow/white wire is currently on the bottom solenoid output as you look at the starter through the grill, is that correct?

[lrostoke]

white/yellow is in the correct place, try unplugging it, and see if you get 12v off that terminal with the engine running, should only be 12v when the starter is spinning.

[dwealds]

I have tried that before and it doesn't matter whether the yellow/white is connected or not I still have 12v on the coil when running.
I also train earthing the - on the coil to the block with the ignition on and the voltage dropped to 4.5v! Seems a little low to me?

[dklawson]

If you are using a digital multimeter to measure coil voltage with the engine running you are not likely to get an accurate measurement. The digital meter will "sample" several times a second. The points (electronic module) could be closed or open at any given time when a sample is taken by the reading. The result is an average voltage that can vary up and down quite a bit. Tiger's suggestion of shorting coil (-) to earth with the ignition on and engine not running is the only way to get an accurate measurement.

When you measured the 4.5V with the coil (-) earthed and engine not running... where did you measure between? Were you measuring from coil (+) to earth or from coil (+) to coil (-)?

[dwealds]

I measured it from coil + to a body earth. Is that right?

[Dan]

Are you using the Lucas electronic dizzy and electronic coil to go with it? If so it needs a straight 12v supply, although it is a ballasted system and uses a ballasted coil. The ballasting is handled inside the dizzy module electronically. The electronics manage the available voltage so that the coil always gets as close as possible to the correct voltage, rather than the fairly crude electro-mechanical standard ballast system. From the sound of it you are supplying this setup with ballasted power. The module needs 12v, if it gets a ballasted supply it burns out in about 2 years but takes a few coils out first as it slowly fails. If however you have got the module at 12v and the coil on the ballast by itself, then you are now double ballsting the coil. I believe this can also damage the module. You should get it all onto 12v, then get the module tested by a Lucas dealer. If you can't find a Lucas dealer to test it, or if it fails, you should ask whichever supplier told you to run it on the ballast to furnish you with a new one.

If you are using the Lucas system that is. The aftermarket electronic systems don't do this, and different models have different requirements regarding ballasting.

[dwealds]

I'm not 100% on the make of the coil or dizzy, I'll have to check it. Minispeed fitted them when the car went in for a tune up and it kept hunting on idle, the dizzy was found to be the issue and idled fine once the new one was fitted.
The current system is a ballasted system.
So if I was to put a 12v supply to a 12v coil could that fix the issue if I have a Lucas dizzy?

Sorry for all the questions but I had to read your reply about 10 times Dan but thank you very much!

[Dan]

Yes, if it's the Lucas modular electronic dizzy with the black module fixed to the side of it and a coil with electronic written on it then the whole lot needs 12v. Not a 12v coil you notice, the proper electronic type coil which is a ballast coil but with about half the primary resistance of a normal ballast coil. Around 0.8 ohms.
If it's any other system then get a picture or the make and model and come back to tell us what it is.

[dwealds]

This is the dizzy and coil that Minispeed fitted:

http://www.minispeed...tributor-vacuum

http://www.minispeed...eapi_node/11410

Was that 8 or 0.8 ohms?

Is it not possible to run a standard 12v coil with a electronic dizzy then? Just wondering as the last distributor that was fitted was the cause of the problems.

[Dan]

The dizzy in the picture is the Lucas electronic one. Slightly confusing that they are describing it as a Yellow because that normally refers to a distributor modified for fast road use by Aldon, but Aldon don't use the electronic type dizzy for their mods. You should check with Mini Speed exactly what it is. Normally that dizzy must not be used with a standard 12v coil, it will be damaged if you do. It must be used with the coil you linked to, which is an electronic ballasted type but needs a 12v supply as I said. If they have changed the electronics then it might be different but calling it a yellow would normally mean a change to the mechanicals and not the electronics.

Sorry I meant about 0.8 ohms, now corrected above.

[dwealds]

They definitely didn't change the electrics that I saw, they went and got it off the shelf and fitted it to the car, connecting the red wire to the module to the + on the coil and the black to the - if my memory serves me right and they also fitted the coil that i linked to although it is still fed by the white/pink wire which i presume is wrong from what you've said?
It says about it having a yellow vac, does this mean maybe that the advance works slightly differently for a higher lift cam? I'm running a 286.

[dwealds]

Got a little update. I tried wiring it up as per your write up Dan on this thread

http://www.theminifo...__fromsearch__1

It still does the same thing, I crank it and it turns but struggles (not a flat battery I've checked all of that over and the battery is a month old). Could it possibly be something to do with the timing? It is making a similar sound to when an engine is trying to fire to close to TDC

[lrostoke]

you haven't moved the HT leads in all your checking ???