electronic ignition

[Eric R]

when installing electronic ignition units in the distributor how important is the HT lead material? I have had three breakdowns of the unit caused by copper and then carbon leads but still the same result after a few months.

[lagain]

Could it be that the electronic ignition is putting out too many volts.
There should not be any problem with the leads.
What sort of electronic ignition is it ?

[enigmas]

Your electronic ignition system should give reliable service if fitted correctly. What make is it? Use the correct ohm rated coil for the ignition module otherwise you'll kill it in no time. Don't open up the plug gaps unnecessarily as it loads the system (.030" is sufficient) Ensure the plug gaps are consistent with sharp edged electrodes when resetting old plugs (sparks jump across sharp edges more readily) Don't use solid core (copper) leads with an electronic module.

Carbon core leads break down eventually and require replacement on occasion. You can measure the resistance with a multi-meter if you know how.

The system you're using will only put out the voltage necessay to produce a spark based on the condition of the current electrical components transmitting the spark. Old or damaged leads, large plug gaps and poor insulation will tax the system to the max. Discounting whatever the make of the system is, it will not produce too much current across the plugs. This is a furphy. It will only produce what is required to jump the gap at the plug.

Unfortunately plug leads wear out and eventually break down. So they'll need replacement from time to time. Severe, cold weather and roughly pulling plug leads off the plugs breaks the carbon core of the lead, creating an open circuit or high resistance.

My preference is for quality brand 'spiral core conductor ignition wires'.

www.magnecor.com/magnecor1/truth.htm

[djm16]

WOT he said.

I have two Rovers with Pertronix, magnacore and iridium plugs, been running them for years.

[Eric R]

the Powerspark unit was recommended by Stokes www.jswl.co.uk/ one of the best restorers in the south of England if not the country in September 2014. I recall discussion about HT leads but i am not sure if they were changed to copper at that time. Time charged 4.5 hours which seems a lot. HT lead replaced now three times copper at this time. ignition unit replaced November 2015. Plugs replaced. Considering the time/mileage thats a lot of parts replaced.
My present garage electrician reports: old coil as fitted primary resistance 3.3 ohms secondary resistance 8700 ohms tested ok
replacement coil primary resistance 1 ohm secondary 6700 ohms tested ok but low primary
12 volt ignition feed to coil present no pulse from electronic unit and no spark to plugs. Suspect power spark ignition unit fault. Powerspark now say that the fault will be copper HT leads and that carbon is required. At their suggestion i have order carbons leads and a third unit but im not convinced.
Accuspark Technical say copper should not be employed, Luminition and Pertronix websites are silent.

[djm16]

A 1 ohm primary is a bit low. When your battery is fully charged, the primary may see as much as 14.8V (alternator) or 15.5V (generator) engine running. So it will be passing 14.8 to 15.5 amps, otherwise known as a shedload. The secondary winding current will be limited 90% by the secondary winding resistance 6-8Kohms. At 100ohms per foot, carbon core cables will not be significant.

[enigmas]

Eric you seemed to either have not read nor understood the technical literature for your particular module. Why did you initially use copper core spark plug leads? (An absolute no go with electronic ignitions.) Your module's technical data will also state an absolute voltage figure. Measure this at the coil positive feed with the engine running. It should probably be no more than 14.5v. If it's more it will most likely overheat the module which will then stop functioning until it cools down. Eventually it will die completely.

NB. If you car has a loom with a built in wire resistor of say 1.5 ohms feeding power to the positive side of the coil, use a coil of 1.5 ohm primary resistance. This gives a total of 3 ohms resistance.

If you're confused by these technical aspects, take it to a competent auto electrician who should be able to fit it aand make it work reliably with their eyes closed!

[Eric R]

thanks for your interest Enigma but being very short in the knowledge, thats why the car was with the world's best car restorers, which is why I didn't read or even need to see any product information and which I wouldn't understand as you correctly state. The unit was their recommendation and which they spent 4.5 hours installing for first time and a further 2 hours replacing. Their skill and knowledge is what I am paying for after all.
The reports I showed in the previous post is by a qualified auto electrician who I have to rely on as well.
Incidentally I am further advised by Lumenition that either copper or carbon HT leads are appropriate on their Optronic product.

[enigmas]

May 6, 2016 14:38:51 GMT Eric R said:

thanks for your interest Enigma but being very short in the knowledge, thats why the car was with the world's best car restorers, which is why I didn't read or even need to see any product information and which I wouldn't understand as you correctly state. The unit was their recommendation and which they spent 4.5 hours installing for first time and a further 2 hours replacing. Their skill and knowledge is what I am paying for after all.
The reports I showed in the previous post is by a qualified auto electrician who I have to rely on as well.
Incidentally I am further advised by Lumenition that either copper or carbon HT leads are appropriate on their Optronic product.

Hi Eric, my comments are not intended as negative or derision. The electronic module you're having so much of an issue with is a Pertronix clone. There are many versions on the market and they all function if the tech data is understood. The pertronix literature will in all probability apply to your system too. The modules current capabilities are very specific and if it is not properly assessed during instalation it will either fail to operate (too little voltage) or overheat and stop functioning after a short time (too much voltage). It will eventually burn out with too much voltage.

The solution to your issue is two-fold. First measure the current output to the coil with the engine running and then add the required resistance. (I outlined how to do this in my previous comment)

Secondly, use carbon core or spiral core plug leads not copper strand wire leads as used in 'old tech' points style car and motor bike ignitions.

NB. I responded to your initial query to this tech forum because you were obviously looking for a solution (despite the best efforts of the current experts you've employed) to an issue that is causing you considerable consternation.

Please ignore my comments if you believe they are of little value in solving your current technical problem.

[djm16]

Aha, I think Enigmas has hit the nail on the head. This is conjecture, but it fits.

(COI I have a 3-litre which has different wiring which is why I did not think of this on my own).

If your auto electrician used the coil +ve lead to power the electronic unit, it will be feeding through a built in ballast resistor. The purpose of the ballast resistor is to reduce the voltage across the coil - fair enough if it is a 6V coil. However, supplying the electronic unit through the ballast resistor will create a power supply to the electronic unit that:

a) jumps between 12V when the "points" are open and 6V then the points are closed
b) much worse, the back emf of the coil at the time of "points" opening may well cause the power supply to the electronic unit to swing negative. You would need an oscilloscope the test this hypothesis.

All of which might explain why normally very robust units are dropping like flies.

[Phil Nottingham]

There is no ballast on 3 Litres - standard Lucas HA 12v coil should be fitted reverse wired if car polarity has been changed from positive to negative earth

[enigmas]

Ok, this is for anyone who is struggling with a pertronix style electronic ignition on any car. The maximum voltage the module can handle (please check your literature) is around 14.3v. If after fitting the unit and driving for a half hour or so and the engine starts to falter then eventually shuts down...the cause is too great a voltage to the module. If the car is then left for half to three quarters of an hour, it will generally restart and run perfectly until the same cycle repeats itself. The module will evntually burn out though unless this problem is addressed.

Some alternators and generators pump out well over 15 volts. This can be checked with a good multimeter. This is not what you want for this system. Points ignitions don't seem to care too much about the over voltage. These modules are available for both positive and negative earthed cars.

The first task is to get the regulated voltage down to no more than 14.3v. Fit a new or rebuilt regulator/generator/alternator, whatever the fix is. Once this is done, obtain the correct coil with the recommended primary resistance for the number of cylinders of the engine. A module fitted to a 4 cyl car will have more 'dwell' time to saturate the coil...hence the primary resistance of the coil will need to be greater. Perhaps 3 ohms. (The instructions will outline the most suitable coil to use.) An 8 cyl car fires more often, so the coil saturation is less...hence the need to use a coil of lower ohm value.

If you car (whatever the make or number of cyls) has a resistor built into the ignition circuit within its loom then that should be added to the primary resistance of the coil you're using to obtain the correct total resistance.

Eg. If your car requires a 3 ohm coil and the power to the coil is direct and always at the same voltage as the generator or alternator is putting out, then use that coil. If your car has a resistor built into its ignition circuit then you need to use a coil with a primary resistance that will add up to 3 ohms when the ignition circuit (with the built in resistance) is added. (Resistance in the ignition circuit 1.5 ohms + 1.5 ohm coil = 3 ohms...or various combinations of the two to arrive at 3 ohms.

The coil you have presently fitted to your car may not be suitable. These modules are very reliable but run a fine balancing act. The trick is to set them up correctly.

NB. As an aside, I went through this exercise with my daughter's 68 Ford Falcon.

Further Note
If the car has an unballasted feed from the "cranking" position of the ignition switch, that feed can also be used by piggy-backing it to the + connection on the coil. Although this will be full system voltage, the voltage is only applied momentarily whilst cranking to start the engine. Once the engine has fired and the starter key is released, voltage to the coil is then supplied by the ballasted ignition circuit. The additional unballasted votage is only momentarily supplied to the ignition circuit to counter the heavy current draw of the starter motor. The module is unaffected by this unballasted feed during cranking and initial engine firing up.

Powerspark instructions

[djm16]

Eric, what car are you fitting the ignition unit to, P5 or P5B?

[Eric R]

to the P5 3-litre Mk1. I might not even go down that route for the V8 3-litre having this experience!

[lagain]

I don't want to hijack the thread, but;
I have had the same Luminition since, probably the late 70s.
As I have a car with the armoured coil when the key is turned all the power goes off and as it was not possible to connect to the power on the coil I took a lead from a constant supply on the fuse box, this goes to a switch similar to the screen wash, so when I start her I push the switch and turn the key, just wondered if there is any way around this.

[Simon H]

May 8, 2016 20:13:51 GMT lagain said:

I don't want to hijack the thread, but;
I have had the same Luminition since, probably the late 70s.
As I have a car with the armoured coil when the key is turned all the power goes off and as it was not possible to connect to the power on the coil I took a lead from a constant supply on the fuse box, this goes to a switch similar to the screen wash, so when I start her I push the switch and turn the key, just wondered if there is any way around this.

I'd suggest tapping into the coil +ve feed from from behind the ignition switch (the wire in the armoured trunking to the coil). My car once had the theft proof system but a previous owner had cut off the coil end of the armoured bit and installed a traditional coil. The +ve feed to the coil is the only ignition key controlled 12 volt supply I can find that doesn't drop out when cranking. But maybe now you have a more theft proof set up than the original works system which wasn't really very 'theft proof' at all...

[Phil Nottingham]

Apart from cutting the ignition key end of the armouring and tapping into the feed you can fit the ballast shunt solenoid cap to the starter motor. It may have it anyway (this is an extra 6.3 male Lucar) and if not the terminal is still there but its just a blob of solder. A cable is then run to the ignition module (and also an electric fuel pump).

The ignition wiring on TP coil cars is a mess and a very poor effort by BLMC 

[lagain]

Thanks for the replies, I will see what I can do !