Questions on voltage to the coil

[moparedtn]

On my 1968 GTX, a former (now deceased) owner (who was a mechanic at a Dodge dealership) had converted the car to electronic ignition, actually doing all the wiring himself versus using the Mopar electronic ignition kit.
The car currently is running all the typical factory-type parts for this:
-Mopar electronic voltage regulator, which I've just replaced with a new one
-Mopar type ECU and electronic distributor
-dual ballast
-MSD coil is new

I'm getting the following voltage to the coil:
-key ON, not running: 2.2V
-cranking: 9.4V
-running: 4.3V

Questions:
1. These voltages seem low to me. Are they?
2. I wonder why he used a dual ballast instead of a single one. Why would someone do that?
3. Do ballasts get "weak" with age or are they simply "working" or "not working"?

TIA!

 

[moparedtn]

Anyone?
This is the ballast on the car now. I know each side has a different resistance rating, but I'd like to make sure that he's got the connectors going to the right posts. Looks pretty easy to mistakenly install it upside-down?

 

[Jackpot50]

Got electronic ignition, ditch the resister you don't need it.
check it with out it.

 

[69Runner]

IIRC the resistance to the coil side (blue to blue+brown) should be 0.8 to 1.2 ohms.

 

[moparedtn]

Got electronic ignition, ditch the resister you don't need it.
check it with out it.

With Mopar electronic ignition, they specifically say you gotta keep the ballast.

 

[moparedtn]

IIRC the resistance to the coil side (blue to blue+brown) should be 0.8 to 1.2 ohms.

Thanks, but what should that read in volts @ the coil?

 

[69Runner]

Thanks, but what should that read in volts @ the coil?

I'm not exactly sure, but I was thinking you could at least verify that side of the dual ballast.

 

[furryfrog]

What is the voltage rating of your new msd coil? Likely has a 12 volt primary side. It is my understanding that ballast resistors are used to drop the voltage to the coil because the stock coil primary side is wound for less than 12 volts.
Seems like your car is running, What is the problem, weak spark?

 

[440beep]

Some troubleshooting articles.

http://www.fourforty.com/techstuff/ignition.html

http://www.mymopar.com/index.php?pid=115

 

[moparedtn]

What is the voltage rating of your new msd coil? Likely has a 12 volt primary side. It is my understanding that ballast resistors are used to drop the voltage to the coil because the stock coil primary side is wound for less than 12 volts.
Seems like your car is running, What is the problem, weak spark?

I'll try not to write a novel here...
If you'll check out my other thread titled "I need to hear from anyone running an Edelbrock 650 on their 440, please!", last page or so, you'll see what all my efforts to diagnose came up with - but in a nutshell yes, the engine managed to not only stumble all over the place at over 4k RPMs but to fuel foul a set of plugs with like no miles on them.
Here's the thing. Previous owner, a dealer mechanic most of his life before he passed on, didn't simply use the Mopar kit when he converted the car to electronic ignition. That much is evident.
When we buy an ECU for our Mopar electronic ignition systems (orange box/chrome box/etc.), we typically get one with 4 pins (the 5th pin spot is vacant). According to all I've been able to find (and according to the installation instructions for the "kit"), a SINGLE ballast goes along with that 4-pin ECU:

True enough, you're issued a single ballast resistor with the kit.

The ONLY reference I can see for a DUAL ballast resistor is in conjunction with a 5-pin ECU:

Well, obviously my car (and most others running Mopar electronic ignition, I'd bet) only has a 4-pin ECU and as far as I can tell, that's about what you're going to get at the parts store or from Mopar Performance.

Now, having said all that and not knowing why "John" did what he did since he's gone, I'm left wondering why he used a dual ballast (remember, he had to wire the car for it, too) but didn't use a 5-pin ECU?
Everything I've read says that when the car is being started that the ballast is bypassed and straight shot 12V hits the coil. Well, not on mine it doesn't....
so if that is wrong on mine, are the "Running" and "Key ON/not running" voltages wrong as well?

Hence my original questions on whether the voltages I'm getting are close to correct or not....

 

[Xp29h]

From what I understand you are correct with the Mopar electronic ignition. I had that in the charger and was using the ballast still. Unfortunately, I never checked the voltage reading. When I upgraded to MSD system, box and coil, I needed to bypass the ballast as the 6AL2 wants all the voltage it can handle. It's the MSD ignition box that needs the ballast bypassed.

 

[69Runner]

Ok, I repeated the voltage measurements, this time measuring from a good ground to the +ve post of the coil.

Key in RUN - 7 VDC
at 600 rpm idle - 10.5 to 11 VDC
1000 and higher rpm - 11.5 to 12 VDC

 

[69Runner]

Hence my original questions on whether the voltages I'm getting are close to correct or not....

Three voltage ranges here:
1) KEY ON ~7 VDC
2) IDLE ~10.5 to 11
3) Revving to 1000 rpm showed 12VDC

Points, stock coil and upgraded VR. 1.0 ohm ballast. Hope this helps.

 

[moparedtn]

Three voltage ranges here:
1) KEY ON ~7 VDC
2) IDLE ~10.5 to 11
3) Revving to 1000 rpm showed 12VDC

Points, stock coil and upgraded VR. 1.0 ohm ballast. Hope this helps.

Man, I sure do appreciate your doing this for me!
You surely are getting different readings than I am.
Only problem is, you've got points. I wonder if it's supposed to be different values for electronic?
I know when you use the Mopar conversion kit, they give you a new ballast to use and I just went and looked up replacement ballasts for a points-type Mopar and a '72-later (electronic ignition) one and they call for different part numbers; it appears the ballast for points-types are rated at 1.35 ohms and the electronic ignition ones are rated 1.2 ohms.
In other words, I should actually be getting more voltage at the coil than you are??

On the other hand, the kit doesn't require you to replace the old coil used with points when doing the conversion, so...
I dunno. I'm almost thinking maybe ol' John wired the ballast "backwards" in that the 5.0 ohm side of it is actually going to the coil instead of the 1.2 ohm side?

 

[moparedtn]

Ok, I think I have some answers here. This is as my car is currently wired:

Now, see how the ballast is basically upside down? The LOWER resistance side should be going to the + of the coil, but instead the HIGHER side is!

Also note the resistance values I got. They're both not exactly right, either. Ballast is probably close to dead.

Here's the kicker, though - see the "green/red" wire coming from the top side of the ballast to the #3 pin of the ECU?
The #3 pin of the ECU is the "missing" pin in a typical 4-pin ECU.
In other words, that voltage is currently going NOWHERE.

Typical ECU:

(Note #3 pin "missing")

Now see if y'all come to the same conclusions I am here:
1. The top side wiring of the ballast is basically worthless as it stands now. It goes nowhere and obviously isn't needed in order for the car to run - because it DOES run, just not as well as it should.
2. "John" must have used a wiring diagram for an old double ballast installation, but he got the ballast turned upside down. Not only that, but it apparently didn't occur to him that he'd need a 5-pin ECU in order for the double ballast to work as intended.
3. The actual wiring job is pretty much correct, as far as it went.
It appears I can simply buy a new SINGLE ballast of 1.2ohm value and plug the bottom part of both sides of my current ballast plug-ins to it.

That current 2.3V going to the coil + isn't making a whole lot of spark, which WOULD in fact explain the issues I've been having with fouled plugs and loss of power on top end
It should be a ton better with that voltage to coil + going through a 1.2ohm resistor rather than the current 3.8ohm, eh?

Make sense?
My head hurts now.

 

[SlinktRR]

That's way low. I run 9-10V in run, 12V startup, as low as 7V running at idle.

2.3V??? Can't believe it runs.

Anyways, you could try rotating the ballast to get the resistances lined up with the right circuits. I use the single ballast, 0.8 ohm nominal from MSD and Blaster II coil. Could convert to single ballast...or just go MSD 6AL or something.

 

[moparedtn]

That's way low. I run 9-10V in run, 12V startup, as low as 7V running at idle.

2.3V??? Can't believe it runs.

Anyways, you could try rotating the ballast to get the resistances lined up with the right circuits. I use the single ballast, 0.8 ohm nominal from MSD and Blaster II coil. Could convert to single ballast...or just go MSD 6AL or something.

Yep, I reckon things are about to get a bit better under the hood.
I thought about just flipping the ballast over, then figured heck, go on and get the right ballast as Ma Mopar intended.
I sure have a nice collection of new spare parts because of chasing this issue...

 

[moparedtn]

Update:
PROGRESS! I'm so happy I could just....well, you know.
Bought a 1.2ohm single resistor from NAPA today (Echlin brand, made in USA) and stuck it on there.
Turned the key to ON and got 4.5V to the coil +.
That's about double what I got before.
"That's encouraging" I thought...

Gave it a couple pumps of the throttle and cranked her up (I don't have any choke set up on the Edelbrock).
I could tell the difference instantly. None of the usual stumbling around until it got some heat in it - it basically held an idle after me keeping it going for like 15 seconds.
That's even more encouraging....

Grabbed the meter and first checked voltage at the battery (remember, I've put a new voltage regulator on it as well but hadn't checked it out yet). Battery showed charging @ 14.4V.
That's encouraging, too...
Put the meter back on the coil + and got 7.5V @ idle (I was getting like 4.3 before).
The engine was noticeably happier sounding, like it wasn't laboring as much.

Well, there's only one more test to do, I thought.
Got behind the wheel and let it build a little heat in the engine, then gave it steady throttle input, making it climb up through the RPM's slowly and smoothly.
It seemed a LOT smoother all the way up.
It got to the "magic" 4k RPM threshold (where everything historically started falling apart in the past) and it was still smooth, so I went further - all the way up to 5500RPM!
Let it get up to 180F and then started aggressively gunning it, revving up past 5k two or three times in quick succession.
No stumbles, no falling on its' face, no popping or misfires.
It acted like a damn Mopar!

Now sure, I still have a little tuning of timing and carb and such to do I'm sure, but it's in the damn ballpark for the first time literally since I bought the car; we're talking more than a few YEARS here.
The engine actually sounds healthy, thank God.

I know I sound all dramatic here, but those of you who've read all my threads here in the past about all the things I've tried to chase this problem down....
the word "relief" doesn't begin to describe it.

Only question left is - do I go with a lower value ballast to increase voltage at the coil a little more, or is that even beneficial at this point?

THANKS EVERYONE for helping!

 

[383man]

You should read from about 6.5 to 7.5 volts at the coil + side with the key on eng off and points closed on a point ign. You are still a little low and could most likely use a ballast with a little less ohms. If you have a 1.2 ohm ballast at room temp you might try a .75 ohm ballast. Also be aware when you measure the ohms of the temp as they will change a little by temp but they change most when on the car running. If the car idles for a bit the ballast will heat up a little and drop the voltage a tad as at idle you dont need as strong a spark. Driving at 4000 rpm or so the ballast will cool a little because at higher rpm there is less time the current flows through the primary system or the points are not closed as long so less current through the ballast will let it cool a tad and the ohms will drop letting more volts to the coil for hotter spark at higher rpm. Not all ballast are like this but most Mopar ones are. GM and Ford used a resistance wire in the wire harness on their older point cars as they all used used a resistance in their point ign systems but Mopar is the only one of the big three to use and externally mounted ballast as Ford and Chevy used the resistance wire in the harness.
Remember on the 5 pin ECU's you need to have the dual ballast where one side is about .75 to 1.25 ohms and that side needs to go to the coil + side. The other side of the ballast is 5 ohms and it goes to the 5th pin which is just a key on circuit to the ECU as the ballast gets 12 volts with the key on to the 5 ohm side of the ballast and the other side goes to the 5th pin on the ECU which is the circuit thats dropped when they go to 4 pin ECU's.
One other thing is that Mopar still used the ballast when they went to electronic ign but Mopar Muscle wrote an article saying you can take the ballast out of the Mopar 4 pin ECU box system and it will still work fine. Well I run the MP 4 pin orange ECU and I took my .75 ballast out to see how it works and I have been driving my car like this since last winter and so far no problems as the coil also does not get hot and its been working fine. Ron

 

[moparedtn]

You should read from about 6.5 to 7.5 volts at the coil + side with the key on eng off and points closed on a point ign. You are still a little low and could most likely use a ballast with a little less ohms. If you have a 1.2 ohm ballast at room temp you might try a .75 ohm ballast. Also be aware when you measure the ohms of the temp as they will change a little by temp but they change most when on the car running. If the car idles for a bit the ballast will heat up a little and drop the voltage a tad as at idle you dont need as strong a spark. Driving at 4000 rpm or so the ballast will cool a little because at higher rpm there is less time the current flows through the primary system or the points are not closed as long so less current through the ballast will let it cool a tad and the ohms will drop letting more volts to the coil for hotter spark at higher rpm. Not all ballast are like this but most Mopar ones are. GM and Ford used a resistance wire in the wire harness on their older point cars as they all used used a resistance in their point ign systems but Mopar is the only one of the big three to use and externally mounted ballast as Ford and Chevy used the resistance wire in the harness.
Remember on the 5 pin ECU's you need to have the dual ballast where one side is about .75 to 1.25 ohms and that side needs to go to the coil + side. The other side of the ballast is 5 ohms and it goes to the 5th pin which is just a key on circuit to the ECU as the ballast gets 12 volts with the key on to the 5 ohm side of the ballast and the other side goes to the 5th pin on the ECU which is the circuit thats dropped when they go to 4 pin ECU's.
One other thing is that Mopar still used the ballast when they went to electronic ign but Mopar Muscle wrote an article saying you can take the ballast out of the Mopar 4 pin ECU box system and it will still work fine. Well I run the MP 4 pin orange ECU and I took my .75 ballast out to see how it works and I have been driving my car like this since last winter and so far no problems as the coil also does not get hot and its been working fine. Ron

Thanks for confirming all that I've posted above (and recently learned thru research)!
Yeah, I think I'll go with a lower ohm resistor, agree. The MSD coil is rated up to 12V and I'm nowhere near that yet. I see they make a .8ohm, but I'll see if anyone else does.
I've read that MM article too and it makes me a tad nervous, since Mopar Performance always included a new ballast in their electronic ignition kits and say that we need to run one.
I guess in your case of not running one at all, worst case is shortened coil life?
What coil are you running?
I wonder what ohm resistor comes in the Mopar Performance kit? I can't find any specs on it.

EDIT: I found tech data that said Mopar Performance included a 1.0ohm ballast in the old conversion kits.
Also found that MSD says that if their "Blaster 2" coil is not used in conjunction with their own ignition control to use a 0.8 ballast for use on "stock" ignition systems.
Reckon I'll play it safe and fetch a 0.8ohm from somewhere.