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Greetings to one and all Pinzers. I have owned my 1973 712M for 20 years now, and while I've had issues with it, I've managed to keep her going without too much difficulty. Until about 3 months ago.

Early summer, I noticed that while my vehicle would start up without much trouble first thing in the morning, it would sometimes not start after the engine warmed up. After letting it cool down, it would fire up again without issue. I didn't give this much thought until about two months ago I drove it to my local grocery store and even after waiting a couple of hours it wouldn't start at all no matter how much I cranked the motor.

I saw somewhere here that this is typically a symptom of a overheated coil, so I replace it with a new Flamethrower fromo Pertronix. No change. I also replaced the plugs just in case, and still no start. I then replace the distributor cap and cleaned up the rotor as best I could and still couldn't get it to run. I checked the plugs for a spark and saw some but didn't know if it was sufficient to fire the cylinders. I even sprayed ether into the carbs but still no luck. At this point I had the truck sitting in the parking lot for several nights without moving so to keep from getting towed I call my own tow truck to take it 3 miles back to my house where it sits now as I type this.

Looking at other forum topics that suggested the 4500 rpm limiter may have gone bad,I went ahead and jumped the middle connections of the two rows, and still no change. I ordered a new voltage regulator from EI since I read that those things go bad before the coil but once again, no change.

I installed a Pertronix set shortly after I bought the truck 20 years ago and later had a civilian conversion done by Thilo in Prescott. Never had a issue with ignition before so now running out of things to replace I opened the distributor to check the Ignitor. I performed the test as described by EI:

https://support.expeditionimports.com/h ... leshooting

and was getting the normal 24V reading across the Ignitor alternating with 0V as I turned the motor by hand.

Here's where I THINK I may have located the problem: As soon as I connect the black wire to the negative terminal on the coil the measured voltage drops from 24 to about half that. I spoke with Scott the other day and he told me I need at least 13.2 Volts to get ignition.

So why is the voltage a full 24 volts when I measure from incoming wire to groung, also 24 volts measured across the Ignitor but suddenly drops to half that as soon as I fully hook up all wires? I don't mind springing new money for a replacement ignitor is somehouw that or the ballast resistor is the culprit but I don't want to throw more money at this problem unless I have a good idea of where the problem lies.

I know you're focusing on it being an electrical/ignition problem, but
are you sure it's getting fuel?

Just my .02 cents

I'm sure it's not a fuel issue since I've already sprayed ether into the carbs with no response. My fuel filter is transparent and shows plenty of gas in the line.

I've been told that I should expect 24 V at the coil, but as soon as I attach the black wire from the Ignitor to the negative coil terminal, voltage instantly drops from 24 to 12.

This may sound really basic, but have you ensured that BOTH batteries are good? If one battery is good and the other bad, you might read 24V with a voltmeter, but when you put a load on them as a unit they drop to 3 or 4 V output under that load. I had an issue like this on my winch where everything looked right, I tried to refresh the motor and the solenoid because nothing was working, even though the voltmeter looked right, etc., until I put the voltmeter on the battery while I closed the circuit. In my case I replaced one of the the two batteries that was bad and everything was fine after that.

I bought a recharger to top up both batteries after repeated cranking started running them down. This problem began with full batteries so I doubt that.
I am trying to understand if the ballast resistor plays any role in this, but I don't want to just replace random parts like I was doing since EI charges about 100 bucks for a new one.

When you push the start button, it bypasses the ballast resistor and runs full voltage to the coil so you get a good hot spark for starting. Keeping full voltage going to the coil would shorten it's life, so once its started and you let off the start button, power is then routed through the ballast resistor, dropping the voltage to the coil.

-RP

You mentioned you replaced the Pinz coil with a Flamethrower -- which one?

They come with 3 difference resistances; 0.3, 1.5, and 3.0 Ohms. The 1.5 Ohm
versions could result in a large voltage drop across the Ballast resistor. The
0.3 Ohm version likely would not survive the "Start" push bypassing the Ballast.
BTW the power source to the RPM limiter is Hot from the ignition switch so you
would not pop a breaker if the current was excessive.

Did you try putting the origional coil back in place just for yuks.

I have the 3 ohm coil and tried both new and old coils without much change.
I have a full 24 V across the coil until I connect the black wire from the Petronix ignitor, in which instance it drops to about 12 Volts. Is this indicative of a bad ignitor?

If I understand how you connected ...with the Black wire from the Ignitor to the Coil terminal -- correct?

When the "electronic points" close, that wire is then grounded completing the path for current flow in the coil.
With 12V on the "Suppressor" side of the coil that implies there is about 12V across the Ballast as well (you
may have had the Suppressor removed with the civi conversion though).

What is not known -- yet -- is the actual value of the ballast resistor, the current, and what the ON voltage is
across the Ignitor. It would help to know at least what the voltage is from the Black lead to ground when
that lead is connected to the coil. I would expect in the ballpark of 0.5V (Ignitor ON). If it's a lot more than
that your problem might be the Ignitor. Although even with a low ON voltage the Ignitor could still be bad.

Oh! I forgot to ask on the previous posting.....

What was the voltage at the "+" side of the coil when you had the
original coil in place? The stock coil should result in about a 4 to 5V
drop across the Ballast resistor, not 12V.

Incidentally, I forgot I had a stock coil laying around from a PinzSSI
conversion. I just measured the resistance and it came in at about 6 Ohms,
twice that of the Flamethrower, so again if you can measure the voltage
with the stock coil in place you should see a significantly smaller voltage
drop across the Ballast resistor. If this holds, all indications are that
with a Pertronix coil in place you should see a significant drop, and
given these are 12V coils that's protecting your coil. Although that
Ballast resistor under the dash must be pretty warm

With a few more measurements you might be heading to a cause...

cheers

If I understand how you connected ...with the Black wire from the Ignitor to the Coil terminal -- correct?
-Yes, correct.

When the "electronic points" close, that wire is then grounded completing the path for current flow in the coil.
With 12V on the "Suppressor" side of the coil that implies there is about 12V across the Ballast as well (you
may have had the Suppressor removed with the civi conversion though).
-I removed the Suppressor just to simplify things since it wasn't really needed, but there was no difference with it either installed or removed.
-I performed the test described by EI: https://support.expeditionimports.com/h ... -Procedure
and it seemed all good with the Ignitor.

What is not known -- yet -- is the actual value of the ballast resistor, the current, and what the ON voltage is
across the Ignitor

-Okay I've so far only looked at the ballast resistor.(Hard to reach). What value of resistance and voltage and current should I expect if I get it dismounted and
measured?

What was the voltage at the "+" side of the coil when you had the
original coil in place? The stock coil should result in about a 4 to 5V
drop across the Ballast resistor, not 12V.

- Maybe this answers my above question. I should expect a voltage drop across the ballast resistor to be no more that 5 volts I take it?

Thank you in advance.

Chris

I measured 4.5 ohms across my ballast resistor.

-RP

Thanks. I'll check mine tomorrow.

To save you some trouble....you do not have to remove the Ballast resistor -- unless it is determined to be bad.

Why I was curious about the voltage drop across the Ballast with the Flamethrower versus the stock coil is that
this would be a quick test of the Ballast resistor without measuring the resistance or removing it as these two
coils are about 2X different in resistance (thus current). So....if the ballast voltage dropped to about 5V or so
from 12V (e.g. if the Battery is 24V then about 19V seen on the coil "+" terminal) that would pretty much rule
out the resistor as a culprit.

OK, I see that you did the ON/OFF Ignitor test. Well that does prove there is basic functionality there; HALL is
good and power FET turns on. But that is not 100% prof positive, however, a good sign and likely good.

Having gone this far down the road, now I'm wondering if it's time to back up a bit and ask a few questions that
probably should have been asked first Are you sure your timing didn't go off into the weeds? If you rotate
the engine by hand where does the ignitor turn OFF (Black wire goes to Battery voltage) w.r.t. the TDC mark on
the pulley? You might want to just eliminate timing as a possibility. Next, when you do crank the engine, as you
have stated she won't start -BUT- do you here any detonation going on in the engine at all or just stone cold silent?

Well, the vehicle went from starting right up with plenty of power to stuttering when I got down the road about 3 miles and refusing to re-start when I tried 5 minutes later, so I don't think timing is the issue. When doing the Hall effect rest I made sure to rotate the engine by hand till the rotor was pointing at the tick mark for the #1 cylinder. It was only when I connected the black wire to the negative coil terminal that voltage dropped from 24 to 12 volts.

My analog multi-meter is acting weird, can't get it to consistent zero resistance reading, so will borrow/buy a digital one to test the ballast resistor as you mentioned. Fingers crossed!