1970 Dart ignition wiring issue.

[67Dart440GT]

I have a 1970 Dart Swinger with a 318 in the car.

The previous owner had an aftermarket Pro Comp distributor in the car. I have changed it back to a Mopar style distributor with an orange box. The car cranks over fine but I have no spark at the moment.

I have the distributor plugged in.
Black wire from the box goes to the negative side of the coil.
Blue wire with yellow trace goes to the ballast resistor (two blue wires).
When I touch the blue wire from the orange box to the ballast resistor I can hear an electric shock in the coil where the coil wire connects to the coil.

I have about 7 volts to the coil with key on, and the same while cranking.

The previous owner had a brown wire hooked to the positive side of the coil. I connected that the same as it was to the positive side.

Any help would be greatly appreciated.

 

[72Dart6pack]

Find a wiring Diagram for a Dart with the Ecu. 1973 will work.

 

[Mattax]

I have about 7 volts to the coil with key on, and the same while cranking.

This doesn't tell us a lot.

With the meter connected to the battery, measure voltage across the battery with the key in start. Should be 9.5 volts minimum.*
Then connect the negative probe to the coil positive. With the start, measure the voltage difference.
There should be very little differnce between the battery and coil positive with the key in start.
If there is a big diffenrce, then check the connection of the brown and blue wires at the ballast resistor. Then at the firewall. Keep working back to the battery.

If you want to check for voltage drops on the ignition run circuit, measure difference in voltage between the power source and the J2 wire conection at the ballast resistor.
Should be close to zero. A few tenths is normal.

One other quick thing to check.
The ballast resistor should measure around 0.5 Ohms
Some of the aftermarket resistors are 1.2 Ohms and might be just enough to prevent an ECU from turning on during start if battery power is marginal. (The top pin of the ECU connector is its power connection - light blue wire in diagram)

 

[67Dart440GT]

This doesn't tell us a lot.

With the meter connected to the battery, measure voltage across the battery with the key in start. Should be 9.5 volts minimum.*
Then connect the negative probe to the coil positive. With the start, measure the voltage difference.
There should be very little differnce between the battery and coil positive with the key in start.
If there is a big diffenrce, then check the connection of the brown and blue wires at the ballast resistor. Then at the firewall. Keep working back to the battery.

If you want to check for voltage drops on the ignition run circuit, measure difference in voltage between the power source and the J2 wire conection at the ballast resistor.
Should be close to zero. A few tenths is normal.

View attachment 1716101295

One other quick thing to check.
The ballast resistor should measure around 0.5 Ohms
Some of the aftermarket resistors are 1.2 Ohms and might be just enough to prevent an ECU from turning on during start if battery power is marginal. (The top pin of the ECU connector is its power connection - light blue wire in diagram)

Thanks for your help.

I found a few wires inside the steering column connectors that were burned. I replaced some sections of those wires just for safety sake. It looks like at some point that got hot enough to slightly melt the plastic connector.

I have done a few other checks tonight and found the ballast has .9 ohms of resistance.

The ballast has 12v on both sides with the key on when I connect the blue and yellow wire from the orange box.

The brown wire from the harness to the positive side of the coil has 12v in the run position and drops to 6 or so when cranking.

I will try the other things you mentioned earlier tomorrow. I had to fix a few fuel leaks.

 

[67Dart440GT]

Well this thing sure is giving me fits. I am really not sure where to go right now.

I had the battery load tested at the parts store. They said it was good for 731 cranking amps.

I have the wiring correct according to the wiring diagrams. I verified that I had this correct on the wiring harness I had in my Demon. I took this system out of my Demon and it was working fine in that car.

One thing I have noticed that is very strange is that the coil + and - arc when I connect the battery cables. I get the same result when I touch the blue wire from the ecu to the blue wired side of the ballast.

Any thoughts on this or another direction I could go?

 

[Bewy]

If the ProComp was a HEI, then removing it was a retrograde step.

 

[Mattax]

When reconnecting the battery, if there is spark in any circuit after the key switch, then there is power available in those circuits.
Therefore something is wrong. None of those circuits should have power with the key off. My guess would be a cross wire short in the column between J1 (feed to the key) and either J2 or J3.

On the ECU. Since its not original connector, we can't be sure of the colours matching the function.
We can be sure of the pin positions.
The top of the pentagon is power into the ECU. This runs the electronics. It's light blue in my diagram above.
To the right and right bottom are a pair of wires connectec to the distributor's magnetic pickup. These carry the signal to the ECU.
On the top left is the ground control for the coil. It's black with yellow stripe in my diagram above. The ECU connects this with wire with ground. When the when distributor rotor turns, the ECU breaks this connection and then reconnects it.

 

[Mattax]

A piggyback connector is a clean way of adding the ECU power connection at the ballast resistor.

 

[67Dart440GT]

A piggyback connector is a clean way of adding the ECU power connection at the ballast resistor.
View attachment 1716102796

Thanks for the info and help. I will check the wire positions later tonight when I get home. All of this is strange because the set up was used in my previous car with no issues. I am thinking there is an issue with wiring inside the car and that is why the P.O. used the MSD style distributor.

When I connect the batter with the lights off in my shop you can see both + and - Terminals on the coil SPARK. That is what is really concerning to me.

Here is what I found last night.

This is the column connector that has the large black and large red wires totally melted in the plug. After further inspection I noticed the yellow wire was also melted to the black wire.

I cut both the black and red and connected them with new connectors as they were super hard about a half inch away either side of the connector.

I also found this green wire just hanging in the fuse block.

 

[Mattax]

Thanks for the info and help. I will check the wire positions later tonight when I get home. All of this is strange because the set up was used in my previous car with no issues. I am thinking there is an issue with wiring inside the car and that is why the P.O. used the MSD style distributor.

When I connect the batter with the lights off in my shop you can see both + and - Terminals on the coil SPARK. That is what is really concerning to me.

Here is what I found last night.

This is the column connector that has the large black and large red wires totally melted in the plug. After further inspection I noticed the yellow wire was also melted to the black wire.

I cut both the black and red and connected them with new connectors as they were super hard about a half inch away either side of the connector.

I also found this green wire just hanging in the fuse block.

View attachment 1716102833

View attachment 1716102834

View attachment 1716102835

Oh boy.
That's a bit of a mess.

Don't try to start it. Need to fix the main harness.
By main harness in this case I mean the main wires feeding power.

(Technically 'harness' refers to everything wrapped into one assembly. So what you are looking at there is the "instrument harness" if you were looking in the parts book. Part number is on a tag wrapped around the bundle by the headlight hi/lo switch)

 

[Mattax]

I'd start by going over all of the power feeds.
Shop manual will be helpful.

This schematic based off of the shop manual diagram shows the how the main feeds relate and where they go.

In the schematic above follow the red 12 gage wire labled J1 back to the battery.
That, and every wire connected at the welded spice is connected to the battery positive without interuption.

There are two circuits that can feed the coil from the ignition switch.
They are labled J2 and J3. The only difference is J2 feeds the coil through the ballast resistor.
What happens when J1's copper is touching J2 or J3 wire?

So the column connector needs to be repaired or replaced.

The next questions is WHY did those wires melt together?
After all we don't want a repeat.
One possibility is the insulation got damaged during some repair.
Another possibility is high current draw in something connected to switched power.
In other words something was drawing a lot of current and the connections, which always have a little more resistance than the wire itself, got hot and melted. Whether that was due to a short somewhere or additional equipment added maybe you can figure out

Fuse box mess.
There should be one feed that is 12 ga. red with white stripe, connected directto the main splice (hidden in harness)
There should be a second 12 ga feed that is black and is only hot when the key is in run or accessory.

Pink is often used to identify power to stop light, hazards, dome light.

I think I would
1. Disconnect the battery.
2. Diconnect the feeds to horn, key switch (column connector), head light switch, fuse box.
3. Check each one - repair or replace.
4. Track down and identify each of the damaged or previously repaired wires and connections. Makes notes. These are the clues to figure out what went wrong and might still be wrong.
5. Then repair or replace.

 

[Mattax]

This 1967 but its similar.


On the bench

Hot feed on left :::: Switched Feed on Right

 

[RustyRatRod]

Thanks yall. Colin is a friend and I was trying to help him on Facebook, but my electrical knowledge isn't what I want it to be, plus we're a long way away from each other.

 

[Mattax]

Lets get into the fusebox

The basic stuff looks OK.
Lets flip the pic to match the service manual.
Maybe Q2A (switched feed) shows a little bit of heat on the insulation but if the insulation is soft then its just the way it looks.
Hot feed looks fine, Feed from headlight switch to intrument lamp fuse (E1) looks fine.

The mystery in the box is what was on the additional fuse that I labeled options ?
Guessing it was the green and red wires that are now on thier own.

Lets see if one of the listed factory options used those colors.
Did the car ever have A/C, rear window defogger, or a headlight relay?

 

[67Dart440GT]

Lets get into the fusebox

The basic stuff looks OK.
Lets flip the pic to match the service manual.
Maybe Q2A (switched feed) shows a little bit of heat on the insulation but if the insulation is soft then its just the way it looks.
Hot feed looks fine, Feed from headlight switch to intrument lamp fuse (E1) looks fine.
View attachment 1716103040

The mystery in the box is what was on the additional fuse that I labeled options ?
Guessing it was the green and red wires that are now on thier own.


View attachment 1716103046

Lets see if one of the listed factory options used those colors.
Did the car ever have A/C, rear window defogger, or a headlight relay?

The car has ac now but it didn't from the factory. This also has a later dash in it for the ac controls.

 

[67Dart440GT]

I followed this video today and everything in the ignition system appears to be working. The arcing on the coil still happens. And when I crank I have no spark. I did also pull the cap and everything looks OK to me. It has hardly any use.

I will do my best to trace the wires. I have repaired both the red and black wire in the column connectors. I also hooked my Demon column to this harness to try to eliminate the ignition switch and I get the same issue.

 

[Mattax]

There is a short between the circuits.
You have to find the short.

I know I typed a lot.
My goal is for you to learn how to fish.
Especially now as my work is heating up and can't spend much time here.

This question is the key one. Answering this is the first step.

What happens when J1's copper is touching J2 or J3 wire?

Put your finger on the coil positive in the drawing. Follow it back to the power.

You fixed the black wire in the steering column main harness. That's fine.
But answer this. What does that wire do? How does it relate to the run circuits ?

If you want to find the specific short, then disconnect the connections that join the ignition start (J3) and run circuit (J2).

Where do they join?
At the ballast resistor, right?

So disconnect them from the ballast resistor.
If the battery is connected (which I do not advise) one or both will show as hot. You can check this with a test light or voltmeter set to DCV.
If the battery is disconnected, which it should be, use a powered test light, or a multimeter set for resistance or continuity.
Put one probe on the battery cable's terminal or its cnnection at the starter relay. Take the other probe and test at the coil terminal, then the J2 and J3 connectors that were removed from the ballast resistor.

The yellow wire powers the starter relay during start.
Remove it its connection from the starter relay and check that as well.
It should not have continuity to any other wire with the key off. My illustration above shows the yellow S2 directly joined to the J3 in ignition switch. That detail is wrong. They only connect together in the key switch when the key is in start position. Key in all other positions and S2 is isolated.

Before you reconnect the harness, make sure there are no shorts to ground.
I would also do basic resistance checks on the coil.

With the wires fixed should be good to go.
The A/C could have added a large load through the key switch feed. Its the only large load through the key switch that we've identified so far.

 

[Bewy]

What do you mean when you say the coil + & - terminals 'arc' when you connect the battery. Aren't the wires secured with a screw or spade lug terminal? Is the arcing to the high tension tower?