Coil voltage

[44067gtdart]

OK, just wondering if I could get some help on this. I did a 440 swap into a 1971 dodge dart swinger that was originally a slant six. I also installed a ready to run electronic distributor in the 440. Anyway, I had problems starting the car after install. It would start, then immediately stall. I could sometimes get it to run, but it would run very rough. And when I tried to put it in gear, it would immediately stall. Anyway, I switched carburetors thinking it was something to do with the carburetor, turns out it was not. Anyway, I ended up running a jumper wire from the battery to the coil, and it runs perfect. Goes into gear no problem, I even drove it around the block a few times and it ran great. I have not checked voltage at the coil yet. (Meter on loan) Will do that in the morning. I did run a jumper wire at the ballast also after the distributor install. Is there any reason I would not be getting 12 V at the coil? Is there anything simple and obvious? Any help would definitely be appreciated. I checked all the wiring and everything seems tight and in good shape.

 

[GTX JOHN]

Is it a MSD distributor
OR
Something Else?

However, it sound likely to be wiring issue in the car
from your text.

 

[Scody21]

Sounds like your wiring is messed up. Your “start” circuit is at 12V cranking, once started, car uses the “run” circuit and a lower voltage. So depending on what ignition system your using, will dictate what voltage hit your coil. MSD box handles power to the coil and works with one circuit. Mopar uses the ballast resistor and the 2 circuits, “start and “run”

So more detail is necessary for a clear Anwser…

 

[pishta]

Only needs about 6-10v in run position to work. Sounds like your run circuit could be very low voltage due to a bad ballast side or worse.

 

[67Dart273]

I assume this is OEM wiring?
I think "ready to run" varies, you need to follow their recommendation as to coil and ballast resistor if any. If you do NOT use a ballast you need to bypass the one in the car.

In OEM form, with either breaker points or Mopar electronic ignition, the coil will run somewhere from 6-10V with key on/ engine stopped. Running, and with charging system at nominal 14V "running" the coil should see 9-12 or so.

You need to check with whoever you got the dist/ coil from as to ballast

IF YOU USE a system with no ballast resistor, it is important to understand how the ignition switch works and how to handle the chage

Originally, the key feeds juice through the ballast, to the coil in the "run" position. This is normally dark blue, "IGN1" THIS CIRCUIT GOES DEAD WHEN CRANKING

Originally, there is a (usually brown) wire hooked to the coil + end of the ballast, IGN2 the bypass circuit. This comes from a separate, dedicated contact on the ign switch, and it's job is to supply good hot full battery voltage to the coil when cranking

So if you run a system with NO ballast, it is important to bypass the ballast. Use the original coil + wire to feed the coil and ignition

BUT THERE IS MORE. Poor connections, damage, and age in the wiring terminals can cause voltage drop from the key through bulkhead connector and to the ballast. There is MUCH written on this here on this board. This can cause overvoltage/ overcharge as well

 

[Bewy]

Not enough info.

 

[oldkimmer]

If he has a ready to run dist he needs to bypass the resistor to have 12 volts to the coil. Kim

 

[44067gtdart]

If he has a ready to run dist he needs to bypass the resistor to have 12 volts to the coil. Kim

 

[44067gtdart]

Thanks for the replies, Sorry, I have been away for a few days. I am getting 12.7 V from the battery to the bulkhead connector. I am only getting 10.3 V to the ballast. The ballast is bypassed, and I am only getting 10.3 V at the coil. I have not checked voltage under the dash as of yet. Wiring definitely is not my specialty, so if anyone knows where to start, that would be appreciated. Could the bulkhead connection itself be causing the problem? Possibly ignition switch wiring? Wiring from alternator? I am assuming the factory wire to the ballast should be getting 12 V , and bypassed I should be getting 12v at the coil.

 

[oldkimmer]

I have had where they are corroded at the bulk head and that causes too much resistance. Check the wire at the ign switch and see what reading u get. Kim

 

[Bewy]

If your coil is designed to use a ballast res, then the bal res should be used with the coil.
The R to R [ some unkindly call them Ready to Replace ] dist requires the full 12v.

I am facing a similar problem, helping a friend with a 68 Polara. With the Ch wiring arrangement, the only way I can see of doing the above is using a relay.

 

[George Jets]

Put an E-Core coil on it that will run cool with the full 12 volts, and bypass the ballast resistor if that ready to run is some type of HEI distributor.

Like 60,000 volts with the E-Core, nice starts and keeps the spark plugs burning clean.

 

[Ironracer]

Put an E-Core coil on it that will run cool with the full 12 volts, and bypass the ballast resistor if that ready to run is some type of HEI distributor.

Like 60,000 volts with the E-Core, nice starts and keeps the spark plugs burning clean.

Are those available for a stock type ignition?

 

[Bewy]

The E core is the best to use & easiest to wire in because the bal res is eliminated.
However people get sucked in with high voltage claims. 48000v is more than enough for a NA engine. Engine will actually only require 15-30KV to fire the plugs, the rest is in reserve. All else being equal, a 48Kv coil will have a more heat in the spark [ current ] & it is the heat, not the voltage, that ignites the mixture.

 

[George Jets]

I have used the E-Core coil with the stock mopar HEI conversions, works great. They run the full 12 volts and they run cool.

Here are some E-Coils that will work. Nice 2 tabs, flat spade positive/negative posts for easy wiring.

Ebay:

Same thing here but "Red" more money:

Same nice flat spade + - posts.

 

[Ironracer]

I have used the E-Core coil with the stock mopar HEI conversions, works great. They run the full 12 volts and they run cool.

Here are some E-Coils that will work. Nice 2 tabs, flat spade positive/negative posts for easy wiring.

View attachment 1715953655
Ebay:
View attachment 1715953656

Same thing here but "Red" more money:

View attachment 1715953657
Same nice flat spade + - posts.

So I can't just add that coil and bypass the ballast? I'll have to do an HEI conversion?

 

[George Jets]

E-core coil with Mopar HEI conversion:

 

[Bewy]

Iron,
An E core coil usually runs without a bal res & draws too much current to be used with either points or the Ch ECU. If you can find an E core that uses a bal res, then it would be ok to use. And it would be worth it because the E core design delivers more spark energy, all else being equal. The Crane PS91 E core coil can be used with a 1.2-1.9 ohm bal res [ Echlin ICR23 or Wells CR107 ]. Not sure if Crane coils are still available.
The MSD 8207, Summit 850500 & 850615 are all good E core coils but not sure if they will work with bal res. You would have to check.

 

[Ironracer]

Iron,
An E core coil usually runs without a bal res & draws too much current to be used with either points or the Ch ECU. If you can find an E core that uses a bal res, then it would be ok to use. And it would be worth it because the E core design delivers more spark energy, all else being equal. The Crane PS91 E core coil can be used with a 1.2-1.9 ohm bal res [ Echlin ICR23 or Wells CR107 ]. Not sure if Crane coils are still available.
The MSD 8207, Summit 850500 & 850615 are all good E core coils but not sure if they will work with bal res. You would have to check.

Ok, I get it now! Thanks for the explanation!

 

[George Jets]

So I can't just add that coil and bypass the ballast? I'll have to do an HEI conversion?

Needs the HEI module to work with the the E-Core coil. Don't recommend E-core with stock mopar electronic ignition.

 

[Ironracer]

Needs the HEI module to work with the the E-Core coil. Don't recommend E-core with stock mopar electronic ignition.

Ok, so that is the Lil "brain" with the different pins? I've read about that here... Thank You! I get it now!

 

[George Jets]

Ok, so that is the Lil "brain" with the different pins? I've read about that here... Thank You! I get it now!

Yep, just like this:

There is a nice little Aluminum adapter plate that screws to the bottom of the mopar distributors to mount the HEI module to.

It's actually a very nice, simple conversion to do. Then you no longer need the mopar electronic ecu / brain box.

 

[Ironracer]

Yep, just like this:

View attachment 1715953659
There is a nice little Aluminum adapter plate that screws to the bottom of the mopar distributors to mount the HEI module to.

It's actually a very nice, simple conversation to do. Then you no longer need the mopar electronic ecu / brain box.

Dig that! And supposed the Lil "chip" is a ALOT more reliable? And, yes, that looks like an easy one.. looks like less work than going from points to electronics, lol. Haven't done one in 30 years though

 

[pt70]

For a 1976 mopar the coil primary resistance is ~1.6 ohms. the coil secondary resistance is ~10,000 ohms.

 

[Bewy]

The GM HEI module has an important feature for high[er] rpm engines that the CH ECU does not have. So along with not requiring a bal res, the GM unit has variable dwell. The Ch unit has fixed dwell. You need a lot of dwell for the coil to fully 'charge' at higher rpms, & the more cyls being fired from that coil, the worse the problem becomes. Dual point dists were used in the old days as a fix, but not much good. More cyls, less time at high rpms to charge the coil & result is misfire.
With fixed dwell, the dwell is set for max rpm anticipated to ensure coil charges fully. But at idle & low rpm, with all this dwell [ coil has current flowing through it during the dwell period ], coil gets hot. Long dwell is not needed at lower rpms. The GM module reduces dwell at low rpms & keeps the coil cool; it extends dwell at upper rpms to ensure coil gets fully charged with current.