No power to coil

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'73red-duster

'73red-duster

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I'm lost. I have no power at the coil, the bottom left tab on the ballast resistor, and none on the field farthest from the main positive on the regulator. It cranks, and everything else seems to work ok, lights, etc. ICM is new, ballast resistor is new, ignition switch is new, neutral safety switch is new. Where do I look?
 
The path is ignition switch, through the bulkhead connector, and out into the engine bay to the ballast resistor. Most likely suspects are problems in the bulkhead connector, the switch connector where it is under the steering column, and the switch itself.

Go to MyMopar and download yourself a free service manual

Also while there download one of the aftermarket wiring diagrams, which are not as detailed but sometimes easier to follow.

That 73 manual got there because of the efforts of some of the guys right here
 
And post some pics.
Should be two ballast resistors on a '73. Not that there needs to be two with a replacement Electronic Control Unit (ECU), but if we don't know what you have there, it makes it that much more difficult to help you diagnose.

Key in Run, yes there should be voltage at all terminals on the ballast. The one(s) closest to the key should be at battery voltage. The other side will be less if current is flowing through it.
If not, follow the circuit back to the next connector closer to the ignition switch. Probably the bulkhead. Check there, and so on.
 
This isn’t the answer your looking for but check out the Power Probe 3 circuit tester tool. Its looks like a handy little tool for problems like yours.
 
'73 looks something like this.
upload_2020-5-13_17-56-54.png


if that's what yours looks like, and there is no voltage at the ballast terminals or the alternator field terminal, check where J2C goes through the firewall. Then at the column connector.

I think there may be more to the story because it should have started when cranking. Thats because the coil gets power from Ignition 2 during start.
 
Mattax said:
'73 looks something like this.
View attachment 1715527426

if that's what yours looks like, and there is no voltage at the ballast terminals or the alternator field terminal, check where J2C goes through the firewall. Then at the column connector.

I think there may be more to the story because it should have started when cranking. Thats because the coil gets power from Ignition 2 during start.
Click to expand...

That helps a lot. Car is at my buddy's body shop, so I'll check that out in the morning.
 
I have tried to trace everything down. The brown wire is the one feeding the coil, but there is only power going to the coil when the key is in the start position. When in the run position, there is no power to the coil. Is that correct?
 
No.
Key in Run, there should be voltage at all terminals on the ballast. The one(s) closest to the key should be at battery voltage. The other side will be less if current is flowing through it.
If not, follow the circuit back to the next connector closer to the ignition switch. Probably the bulkhead. Check there, and so on.
 
Connector under the dash from the ignition switch, brown wire is only hot with key in start position.
 
upload_2020-5-14_12-40-39.png


In start, the key connects the Ignition 2, and the starter relay wire with power feed.
If while cranking the battery voltage drops to 10.5, then voltage should be around 10.5 up to the resistors.
It will be a little less on the other side of the resistor when current is flowing to the ECU.
upload_2020-5-14_12-57-8.png

If the connector is removed from the ballast, voltage will be the same on both side.
When there is no current flowing through the resistance, there is no drop in voltage.
 
In run, the key connects the Accessory and the Ignition 1 wires with the power feed.
Everything up to the ballast should be close to battery voltage.
If the ECU and the alternator's rotor are drawing current, the ammeter will show a slight discharge.
The coil is probably drawing current as well, so the voltage on that side of the ballast will be a few volts lower than the rest of the system.
upload_2020-5-14_13-11-43.png
 
'73red-duster said:
So the brown wire should carry power In the run position?
Click to expand...

No, brown provides power to coil in "start."

Key in run, engine stopped, coil should measure around 8-10V Running, maybe 10-12V if charging, that is battery should be 14

Key in "start" (cranking) coil should read nearly same as battery, and at least 10.5V while cranking
 
Thank you. We finally figured that out. Cleaned the bulk head connector, and re-spliced some wires. One of those got it going.
 
'73red-duster said:
Also, the ballast resistor gets really hot.
Click to expand...
Yes. That's why its covered in ceramic.
Try not to leave the key in 'run' when the engine isn't running. When the engine is running, the current flow is interupted. (The interuption is what releases energy from the coil to the spark plug). Without interuption both the ballast and the coil will get hotter than normal.
'73red-duster said:
Thank you. We finally figured that out.
Click to expand...
Well by figuring it out, you'll remember it better. :)
 
Last edited:
Sure hope so. Hope to get started on my Duster before too long. I printed off the wiring diagrams you posted. They were much easier to follow, Thanks again for the help!!!
 
@Mattax ,after running all the tests, going by the diagrams you gave me, gremlin still kept returning. I kept telling myself it would end up being something stupid simple. Bad coil wire. (New set from O'Reilly) Changed coil wire, and it didn't even turn all the way over when it fired. Ordering another set from Summit.
 
Sure sounds like there still is a poor connection.
If you post exactly what tests you did and how you did them, maybe we can narrow it down.

I mean, it could be a bad connection in the ignition switch or some wire in the engine bay that got jiggled when changing the secondary wire on the coil.
 
I ran through all the tests using the diagrams you posted. I got to the coil, hooked a test light to it, and when I hit the starter, it pulsated. Pulled the coil wire and put the ohm meter on it, and nothing. Borrowed a coil wire from another car, and it fired right off. Tried it off and on all day, and never failed.
 
Started like this every time after changing the coil wire. I think before we would move it just right and it would start. Had it running once, and when I turned the distributor to set the timing it died, and wouldn’t start again.

Can't get video to upload.
 
I..........don't.........know..........this is a good example of the pitfalls and problems of "troubleshooting by remote control." We ain't there and we can't see LOL
 
67Dart273 said:
I..........don't.........know..........this is a good example of the pitfalls and problems of "troubleshooting by remote control." We ain't there and we can't see LOL
Click to expand...

It’s hard to do, but I sure do appreciate the help. I pretty much get lost on wiring, but thanks to the input here, I’ve learned some things. Also got some things updated that needed done anyway.
 
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