Electronic dizzy conversion

[markymark]

Hi All,
I have purchased an electronic distributor and coil from JRW. It looks a good bit of kit and simple to fit......except I’m having problems.
Before I take the problems up with the manufacturer, I was hoping to run the symptoms past the folks on this forum in case I’ve dropped a ball somewhere.

The distributor has been fitted alongside the new coil. The instructions said to remove the ballast resistor so I have done that. The ignition feed goes to the +ve terminal on the coil. I then have a red wire from that terminal going to the distributor and a black wire from the -ve coil terminal also connected to the distributor.

When I first crank the engine it fires and runs for a second then dies. If I crank again I get nothing. When I am getting nothing I have ascertained that there is no spark even at the coil. There is a voltage at the coil though on the low tension side.

If I leave the car with battery on charge for a few hours I can repeat the whole process. I have checked the voltage at the coil and at the fuse box ignition control. I get 12.7v initially which drops to 9.2v when cranking. Both coil and fuse box read the same. Not sure if that is a significant voltage drop or not.

Any thoughts much appreciated!

BTW the car is a 1970 P5B.

Thanks,
Mark

[eightofthem (Andy)]

if you have a Coupe then the wires to the coil run through the tacho, you might have to run a new supply wire to the coil. Try removing the wires to the tacho first with a new supply live to the coil.

[Phil Nottingham]

Try a temporary connection from the Ignition Control LHS (unfused side) direct to the coil + (disconnect the original feeds)  You may be feeding from the ballast shunt from the starter solenoid which only works when cranking and is failin

[enigmas]

Phil makes a good point...if the power feed is only from the shunt (starter solenoid whilst the engine is cranking) it will only fire for as long as the starter is engaged. Once the starter is released it will cut out.

If there's an internal resistor on the ignition circuit there should be a second wire that you have left off the + side of the coil. This wire will read about 9v with the ignition key switched on. Not the 12v you want but re-attach it and see if it will run. You'll probably find there'll be a voltage increase on this circuit with the engine running so it will probably be fine!

[markymark]

Thanks for the suggestions guys.
I’ve just run a temporary feed from LHS of ignition control at fuse box to the +ve terminal on the coil. Still no spark.
I’m going to contact the manufacturer in the morning to see what they suggest.

[Phil Nottingham]

Must be a fault in the module or its trigger then

[djm16]

While hot wiring should have worked, it is no substitute for a voltmeter across the terminals and to ground.

Operator error is much more common these days than a faulty part.

I too guessed that you were getting your +ve supply only from the starter solenoid.

[enigmas]

If you have inadvertently connected the power wire to the module incorrectly (polarity around the wrong way)...it will be toast, unfortunately!

If it is a Pertronix clone...similar to the one below check that the trigger (the small round device under the rotor button) is not rubbing against the module...there needs to be a small air gap.



Other Points To Consider.

The position in which the Ignitor red wire is attached to is not supplying sufficient voltage.
The air gap between the module and magnet sleeve is too great.
The ground wire inside the distributor is not connected.
The wire connections are not tight.
The polarity is not correct.

[Phil Nottingham]

I prefer the standard points set-up far less bother and tons cheaper

[markymark]

Hi All,
I have spoken with the manufacturer. He advised me to remove the dizzy and lay it on top of the engine, then with the HT from the coil attached to a spark plug, spin the dizzy by hand and look for sparks. That worked. I have a healthy spark.
He is saying that my voltage is dropping far too much under cranking. Should be 12v or close he says.
The next test is to run a cable from the battery to the coil. If that works, it proves that I have an excessive voltage drop somewhere in the loom.

Will keep you informed.

Regards,
Mark

[enigmas]

From what you've just stated/outlined you must either have a ballasted power feed going to the distributor full time (is there an external ballast resistor fitted even on run?)... or a coil with too much primary resistance.

NB.
Your quote from above.
"I’ve just run a temporary feed from LHS of ignition control at fuse box to the +ve terminal on the coil. Still no spark.
I’m going to contact the manufacturer in the morning to see what they suggest."
The comment above is effectively 'hot wiring' (as DJM16 pointed out)...so what changed?

The only thing that has changed is literally physically spinning the distributor drive whilst the distributor is removed from the engine. This negates the voltage drop caused 'seemingly' by the starter motor when cranking as it has been removed from the equation.


There is still a voltage drop even when you take it from a 'full' 12v supply at the fusebox!
Given this, is there an external ballast resistor attached to the coil or is the coil of an incorrect primary resistance rating?

[Phil Nottingham]

Take a 12v supply DIRECT from the battery (or the main terminal on the Stater motor) and see what that does

[djm16]

RE-READ your original post.

In normal car set-ups with the battery under the hood, it is absolutely normal for the voltage reaching the car system to drop to 10V or less while cranking. What surprises me is you do not have a bigger voltage drop across the ridiculously longer battery cable from the boot to the engine bay. That is after all why P5Bs had a 6V coil and ballast resistor.

You have a number of options.
1) throw away the electronic distributor. (Phil's choice )
2) get a bigger battery - go buy a diesel truck battery from a proper automotive store (not Halfords), or direct from a Caterpillar distributor (N70 style).
3) replace the main battery cable with something thicker and newer (and therefore lower resistance).
4) run an independent heavy duty, ignition only lead direct from the battery (clearly you will need a relay to de-activate it when you turn off the ignition).

[Phil Nottingham]

The standard P5B points set up does not need ballast assistance anyway - thief proof models quietly dispensed with it with the Heath-Robinson soon to be EEC regulations for security. 

The cranking voltage is borderline but the electronic ignition is supposed to cope with it.  I have always used 069 batteries on P4, P5 and Landies - anything bigger is a waste of money as there MUST be another problem.

Is the dizzy properly earthed?

If its not the electronic gubbins it will be something dead simple that has been overlooked

I do not think the long cable will give any measurable effect - a lot of cars had such an arrangement even Minis as well as the P4 and Vanden Plas 4 Litre R

[markymark]

Hi All,

I have run a cable from positive terminal on battery to the positive on the coil. Still no spark. Voltage under cranking is now only dropping to 10.2v.
I also ran an independent earth to the dizzy with no joy.

I’ve pretty much had enough now. The car needs to be running as I have furniture due for delivery next week that has to go through the garage. Tomorrow I am going to refit the old dizzy.

Thank you all for your help. Not sure what else I can do. My limited knowledge of these things tells me that a drop to 10.2v isn’t unreasonable and the dizzy should still fire....we will see what the manufacturer says next on Monday....

Regards,
Mark

[enigmas]

Unfortunately Mark you must have wired it incorrectly or the battery is marginal! If you can get it to work with the distributor removed from its housing (as the seller contact advised you to do) by laying it on top of the engine block, it obviously functions.

If you run a wire directly from the battery to the positive coil terminal there won't be a voltage drop in a static condition as there's no load on the battery. If there is a voltage drop to 10.2v as you state, the battery must be cactus and it would surely drop further when the engine is cranking! Substituting the battery with a known 'good' one would remove any doubt.

* Have you replaced the distributor correctly...are you sure the ignition timing is where it should be and not 180° out?

[djm16]

You are right, the electronic distributor should be able to cope with 10.2V.

Try one thing more, my apologies if you have done this already:

put a voltmeter across the coil and watch it while someone else cranks the engine on the key. You may observe:

for a very fast responding voltmeter (old fashioned moving needle sets were ideal for this) you will see the voltage jumo up and down between 0 and 10V.

OR for a very slow voltmeter you may just record an average voltage of 6 or 7v

OR for a typical DVM, the voltage will just jump around at random depending on how closely the DVM sampling period coincides with the on-off cycle of the distributor output.


OR you could just connect a 4w bulb across the coil terminals. You know what 10-12V looks like from the brightness of the bulb. A low power bulb should change brightness quickly enough to show you that the voltage is going from 0 to 10V.

So if you have established that the voltage is going up and down as expected, try replacing the coil.

BTW, a "healthy" spark is a skinny pale blue. A weak spark is a fat orange. Counter-intuitive, but true.

[markymark]

Hi All,
I think I screwed up the earlier test with the dizzy out laying on the engine. I recall seeing somewhat random sparking when turning the distributor shaft and it occurs to me now that actually as I turned the shaft the grounding of the distributor was moving in and out of contact.
What is driving this thinking is that when I turn the ignition on without cranking (first position with green/red lights on) I get an instant spark. Then on cranking I get nothing. Could it be that there is a fault in the dizzy which means it is always trying to spark regardless of shaft position?
Yesterday I tried to test this by putting my voltmeter on the coil terminals. What I saw I don’t think is right. Testing the voltage on the +ve terminal to ground shows 12.7v. Testing the -ve terminal to ground shows the same? Can that be correct? This is regardless of shaft position.

Thanks all...

[enigmas]

Look here Mark www.howacarworks.com/ignition-system/checking-the-low-tension-circuit and read 'Checking the Coil'

If it sparks when you turn the ignition switch on and off it generally means that the electronic trigger switch is active...passing current through the coil (like a set of points being closed). When you turn the switch back/off it triggers a spark as you cutoff the voltage through the coil and it acts as a transformer (similar to when the points open to fire a cyl) producing a high secondary voltage.

PS. If you lay the distributor on the engine block to test for 'spark' you also need to ensure it has a viable ground/earth connected to its case.

NB. So much of these diagnostic explanations is speculation (as far as I'm aware) as no one really knows what type of electronic ignition system you're trying to hook up.

Can you provide a clear close up photo of the distributor with whatever type of module you've fitted?

[johnwp5bcoupe]

Dec 1, 2018 9:27:36 GMT markymark said:

Yesterday I tried to test this by putting my voltmeter on the coil terminals. What I saw I don’t think is right. Testing the voltage on the +ve terminal to ground shows 12.7v. Testing the -ve terminal to ground shows the same? Can that be correct? This is regardless of shaft position.

Thanks all...

If you have the wire off the -ve terminal yes you will have the same voltage!

[johnwp5bcoupe]

Dec 1, 2018 12:40:22 GMT johnwp5bcoupe said:

Dec 1, 2018 9:27:36 GMT markymark said:

Yesterday I tried to test this by putting my voltmeter on the coil terminals. What I saw I don’t think is right. Testing the voltage on the +ve terminal to ground shows 12.7v. Testing the -ve terminal to ground shows the same? Can that be correct? This is regardless of shaft position.

Thanks all...

If you have the wire off the -ve terminal yes you will have the same voltage! if it was a standard points system you would get a short to earth each time the dizzy points open and close

[markymark]

Hi All,
Just wanted to let you all know that I returned the electronic distributor. A new one was then dispatched which works fine.
Thank you for your help and Merry Christmas.

Regards,
Mark

[eightofthem (Andy)]

Result, and thanks for keeping us informed.

[markymark]

Hi All,
As the evenings are drawing in I noticed that she would stall when I put the headlights on. Running a new supply to the coil from the fuse board fixed that problem, but I now don’t have a working tacho.
Is it a case of running a new wire to the tacho or is it more complicated than that?

Many thanks,
Mark

[djm16]

The tacho sensor IS the supply wire to the coil. Every time the coil charges and discharges, a current pulse passes down that wire that is detected by the tacho.