Electrical Gremlins: Roadrunner Dying While Driving and Idling. Help!

[InViolet70]

Hey everyone,


I’m chasing down an electrical issue on my ’70 Road Runner (383, Mopar/Proform electronic ignition conversion about three years ago). Here’s what’s going on:

• Car starts right up and sounds fine.
• This issue started very gradually last fall but I thought it was a fuel issue from it sitting.
• Last week, during an hour drive to MoParty it died while drive down the highway. Start it up and it runs but then would not stay running for longer then 3-10 minutes at a time. At one point it seemed like heat would prevent it from starting but the car was not over heating. When testing yesterday it would run for about 30 secs to a few minutes and die but start right back up.
• Muffler recently blew out, but I am certain it is from it being clogged up and it is a coincidence.
• When testing the distributor pickup coil, I get ~410 Ω.
• Ignition coil tests fine as well
• Ignition Module (little orange box maybe?)
• Ballast resistor could cause it to die when key goes back to run, which is not the case.

Questions:

1. Does this sound like a failing pickup coil even though it tests fine?
2. Does this sound like a failing ignition coil even though it tests fine?
3. How can I go about verify if my little orange box is the culprit?

Today I will be cleaning all electrical lines from the ignition coil, distributor, ignition module (orange box), and bulkhead.


I want to keep the car looking stock but need it reliable. Any input or test steps you guys recommend would be appreciated.


Thanks!

(Threw in a picture of the blown out muffler for laughs. Check out the brand)

 

[Davefinan]

I had that same thing happen to my charger as you described. For me it turned out to be a rubber fuel line at the electric fuel pump by the gas tank. It kinked over time. Yes , I am the one who did the install…..DOH! Apparently I put too sharp of a bend in the hose and it later kinked leading to the restriction.

 

[InViolet70]

I had that same thing happen to my charger as you described. For me it turned out to be a rubber fuel line at the electric fuel pump by the gas tank. It kinked over time. Yes , I am the one who did the install…..DOH! Apparently I put too sharp of a bend in the hose and it later kinked leading to the restriction.

I’ll get it on the lift and go through the lines!

 

[oldbee]

My bet is ign.coil.

 

[WileE]

When the symptom occurs, drip fuel in the carb throat. If the car continues to run, you know it's a fuel issue. ( you can use a spritzer bottle filled with gas ).

 

[InViolet70]

My bet is ign.coil.

now I did test this and it seemed fine. Any reason you think it could still be the culprit?

 

[oldbee]

Just going by your description… Actually, anything electrical usually shows problems when warmed up.

 

[turbine68rt]

When you said it started up right away after it died, it reminded me of the same symptom I had with one of the bulkhead terminals in the main engine harness not making a positive connection and would cut out intermittently. Replaced the bulkhead panel, the female terminal in question, and the harness. Haven't had a problem since then.

 

[MWbirdLOVER70]

Hey everyone,


I’m chasing down an electrical issue on my ’70 Road Runner (383, Mopar/Proform electronic ignition conversion about three years ago). Here’s what’s going on:

• Car starts right up and sounds fine.
• This issue started very gradually last fall but I thought it was a fuel issue from it sitting.
• Last week, during an hour drive to MoParty it died while drive down the highway. Start it up and it runs but then would not stay running for longer then 3-10 minutes at a time. At one point it seemed like heat would prevent it from starting but the car was not over heating. When testing yesterday it would run for about 30 secs to a few minutes and die but start right back up.
• Muffler recently blew out, but I am certain it is from it being clogged up and it is a coincidence.
• When testing the distributor pickup coil, I get ~410 Ω.
• Ignition coil tests fine as well
• Ignition Module (little orange box maybe?)
• Ballast resistor could cause it to die when key goes back to run, which is not the case.

Questions:

1. Does this sound like a failing pickup coil even though it tests fine?
2. Does this sound like a failing ignition coil even though it tests fine?
3. How can I go about verify if my little orange box is the culprit?

Today I will be cleaning all electrical lines from the ignition coil, distributor, ignition module (orange box), and bulkhead.


I want to keep the car looking stock but need it reliable. Any input or test steps you guys recommend would be appreciated.


Thanks!

(Threw in a picture of the blown out muffler for laughs. Check out the brand)

View attachment 1920429

View attachment 1920430

Check for corrosion build up inder the orange box plug (@Kern Dog )

 

[Darter6]

failing ignition coil even though it tests fine?

This just happened to me. A Accel coil that slowly died. Check out fine using the service manual procedure.
First a few hic-ups then stalling at stops/idle then cutting out at road speed. Finally it would start/run for about 30 seconds then die.
I too thought it must be fuel related. Pulled the tank,checked the plck up, blew out the lines.
I have a electric booster pump in line ran it. Mechanical pump was putting out fine.No problems.
The coil had very little time or age. Just a thought.

 

[Don Frelier]

First report back with the bulkhead connector results.

Then I think your likely culprit would be in reverse order of your list

3.ecu
2. Coil
1. Pickup

Parts substitution is probably your best bet

Do it 1 item at a time.

 

[InViolet70]

This just happened to me. A Accel coil that slowly died. Check out fine using the service manual procedure.
First a few hic-ups then stalling at stops/idle then cutting out at road speed. Finally it would start/run for about 30 seconds then die.
I too thought it must be fuel related. Pulled the tank,checked the plck up, blew out the lines.
I have a electric booster pump in line ran it. Mechanical pump was putting out fine.No problems.
The coil had very little time or age. Just a thought.

With two of these cars as is, it won’t hurt to buy another coil and test it out. Thanks!

 

[Darter6]

Just get the right ohm for your ignition system. I took advise from a You Tube channel and ordered the wrong one.
They said the .32 ohm is what they use. Didn't for me.Got a .6 ohm for my aftermarket ignition.
If you are running the Mopar electronic ignition or points a 1.5 ohm is used.

 

[NoCar2023]

Mopar/Proform electronic ignition conversion!!

Do you still have the points distributor?

 

[Kern Dog]

Check for corrosion build up inder the orange box plug (@Kern Dog )

I had an intermittent "no spark" issue that I'm pretty sure that I fixed.
Old plug:

New plug...

The brass terminals were stretched out and corroded on the old one. I changed this some time last year and have not had a single "No spark" issue since.

 

[Dennis H]

Spray Bulkhead Connector with Electrical Contact Cleaner. Half can. Remove, clean, reinstall battery cables for good measure. Cheap. Does it stumble or cut off like key turned off?

Completely disassemble car from front to rear. (Humor).

 

[InViolet70]

Mopar/Proform electronic ignition conversion!!

Do you still have the points distributor?

I do not

 

[InViolet70]

Spray Bulkhead Connector with Electrical Contact Cleaner. Half can. Remove, clean, reinstall battery cables for good measure. Cheap. Does it stumble or cut off like key turned off?

Completely disassemble car from front to rear. (Humor).

Normally just cuts right off like the key is turned off.

 

[NoCar2023]

I do not

You would be better off with it. That Proform kit is junk.

 

[Davefinan]

You would be better off with it. That Proform kit is junk.

I can remember when you could improve these old car’s performance with some aftermarket parts. Now it’s like the opposite.