First let me clarify that I know very little about electronic ignition systems and car electrical systems except they are needed to run the car.

1967 Dodge Coronet R/T, 440HP engine converted to a Chrysler electronic ignition system. This was done more than 30 years ago before I bought the car. The ignition system worked fine for many years but over the last few it has given me fits. What is happening is that I am not getting spark to the coil so it won't start. When I turn the ignition switch off the engine kinda of "thumps" as if it got an instant spark and it feels like it is trying to turn the motor backwards. Occasionally it will start when I release the starter but very seldom. The magnetic pickup in the distributor was replaced several years ago. It now has an MSD coil. The ecu was replaced a couple of weeks ago as it was fried due to the it receiving 17 volts (per the mechanic). He replaced a wire from the voltage regulator to the ballast resistor and the car started and ran fine for a while. He said the alternator was working fine and putting out the proper voltage. But last weekend it wouldn't start again. It also had a brand new battery in it. Does anyone have any idea what is going on and suggestions on how to fix it?

Thanks in advance for your input. I has always helped me in the past and is much appreciated as I love my Mopars but don't always know how to fix them. Bill

Wouldn't turn over or wouldn't start? Two different things.

Usually it's a wiring problem involving the start and run circuits, all the way to the ballast and ECU, all the way to the coil.

Determine if you have 2 or 4 pin ballast, pull a wiring diagram from online and ensure it's wired as it should be.
Look for hack temporary repairs (wires twisted and taped together and so on).

Assuming a 727, pull the yellow wire on the starter relay to the neutral safety switch so the starter won't crank, turn the key to "start" and check coil + voltage.
Then check battery voltage across the two terminals. The two numbers should be basically the same. If the voltage at the coil is
non existant or substantially lower, there's definitely a wiring problem, bad connection, failed switch but wiring/connection problems are most prevalent.
Use a digital multimeter. If you don't own one, definitely buy one, it will help you a bunch.

It turns over fine, just won't start. I try it several times off and on again. It cranks so much that the oil light goes out. At least I am getting oil to the parts.

It is a 4 pin ballast. I assume it is wired correctly as it run wired like this for years. I also have a wiring diagram that a friend gave me.

It is a 727. The mechanic said he checked the voltage as you stated but I will check it again. Could it be the ballast resistor has gone bad?

As Zippy said, you have a wiring problem.

In NORMAL operation,

While running the ignition switch powers the run circuit which powers the coil through the ballast resistor.

While starting the ignition switch powers the start circuit, this bypasses the ballast resistor and powers the coil with full battery voltage to improve starting. You are not getting this voltage at the coil.

As a quicky confirmation, run a jumper wire from the battery + to the coil + and see if it starts.

The "bump" you are feeling happens when you release the key and the run circuit powers up letting the coil spark. It's not enough to actually start the car though.

Since this is an add on system the stock wiring diagram may or may not help.

The ballast resistor plays no part in the start circuit, any suggestions that this is the problem are given by those who do not know how the ignition system works, The closest it gets to being involved is being a place for the wires to connect. The fact that you are getting the "bump" as you call it tells us the ballast is ok.

I dug out my 67 FSM.

The STOCK wiring colors and what they do are as follows.

At the ballast

Dark Blue goes to the coil, this is the coil power lead in start and run
Brown hooks to the same side of the ballast as the Dark Blue wire above, this is where the voltage to power up the coil in START comes in ans is probably what is missing. This wire goes thru the bulk head connector ti the IGN2 terminal on the ignition switch.

On the other side of the ballast you have one wire, a Dark Blue one. This one provide voltage to the ballast in RUN, the power goes thru the ballast to the coil, again in RUN. The Other end of this wire goes to the IGN terminal on the mechanical voltage regulator.

2 quick tests you could do to prove it one way or another.
leave the key in the run position and jump the starter relay.
OR
wire something to the ballast from the battery pos cable then use the key to try and start the car.
both should act the same and should let the car start.
this tests shows there is something wrong with the start circuit.
the ballast is bypassed during the start cycle but in use during the run.

The starter relay plays no part in the ignition system.

Disconnect the engine harness connector at the distributor, turn on the ignition switch and touch the male prong on the engine harness to ground. Each time the prong is grounded and pulled away you should get a spark from the coil. If it sparks, the distributor pickup is the problem, if not it's the primary wiring, ECU or coil.

Thanks for all of the input. Looks like I have some testing to do tonight or tomorrow. I will let all of you know my results.

He is saying jump the relay to crank the engine with the ballast hooked to battery power.It's eaiser then having to reach in to turn the key. He isn't saying the relay is part of the ignition.

Sounds like a bad ballast resistor to me. As stated. Put the key in the run position and I use a starter switch as a jumper. Put one lead on big terminal of the starter relay and the other smaller screw with hex head slotted screw. It should start right up if it’s the ballast resistor is bad. Most carry those as a spare. They go out all the time. You can jump those two post with a screw driver or pair of pliers in a pinch. It just engage starter is all.

I will reiterate, anyone that states the issue in this situation is the ballast knows nothing about how mopar electronic ignitions work.

It is bypassed in start,

The OP gets a bump when he releases the key and it returns to run, that tells you right there the ballast is ok.

Corrosion in the connector from the distributor to the wiring harness. Unplug it and clean the contacts and try it. This has worked for me in the past. Sometimes just unplugging it and plugging it in again scratches the corrosion and the remakes the connection, but it doesn't last long.

Stop throwing parts at the problem, this is a very simple system, perhaps get a new mechanic

Check the distributor pickup by using an ohm meter across the connector.
I do not remember what it is supposed to read but it is simple ohms.
when the distributor spins you can see the meter read the reluctor - the meter will show continuity then an open circuit as it spins
This is known problem that over the last 10 years has crept in due to lack of quality in the parts

Yep. A bad ballast is just the opposite, starts and then immediately dies. I had that happen late one night on the way home. Engine kept dying. I'd have the shift to neutral (auto) and restart it. It would run briefly then die. One time I hit start before I put it in neutral and it refired. So I just held it in start position until I got home.

check the ignition switch wires and plug to see if you have voltage in the start and run positions, and how much it is.
also look for "melty" wires on the switch connector plug, and going from it to the bulkhead connector.

Set your meter on ohms and read between the two wires on the pickup, should read around 300-900 ohms.

Then set the meter on the lowest AC volts and measure the voltage from the pickup when a reluctor blade passes the pickup, should read slightly less than 1 volt.

I have been doing some testing. I do have a remote jumper switch to connect to the starter relay and press the button to activate the starter. But I have to work alone so if I have to check something while pressing the "start" and then hold the leads on the meter, it is difficult. But here are the results on some of the tests I have run.

I jumped the battery to the coil and tried to start, No good, still wouldn't start. I did check the voltage at the coil before starting and it was 12 volts.

I disconnected the wiring harness from the distributor, turned the key to "run" and grounded the male end of the ECU harness and pulled it away several times. No spark anywhere. So the magnetic pickup is apparently okay.
The distributor harness looked clean when I pulled it apart. I did try to start it again after putting the harness back together but no go.

I pulled the wires off of the coil and checked the ohm readings and they looked okay. So I think the coil is okay.

I did try to check the wiring colors. I have a wiring diagram from a friend that shows the wiring from the ECU to the ballast and to the coil. It is basically the same as what Sniper described but different color wires. This is a factory AC car so there are a lot of big hoses in the way at the firewall. And the wiring was done 30+ years ago before my ownership. He used different colors on the wires than either diagram shows. (White wire on the coil + that goes into a homemade wiring harness but doesn't come out at the other end.) I have to assume that it is wired correctly as it has run this way for 30+ years. See the pics below. I have looked at some of the connections and they appear old but still functioning. At this point I will change out the ECU and see if it starts. If it does then that means ECU is fried again. If so that will be the 4th one in 6 months. So that means something is overcharging somewhere. A new issue.

Any suggestions on where to get a new ECU that is of reliable quality?

There were a couple of other suggestions since the last time I checked in that I will try.
Thanks for all of the help