Yet another ECU question

-
crj1968

crj1968

Well-Known Member
Joined
May 28, 2014
Messages
745
Reaction score
354
Location
Idaho
Hello
just purchased a 70 Duster with a 318. when I went to look at it it wouldn't fire. Crank crank crank. Key in run position: voltage at both sides of ballast. tried jump solenoid no go

ran 12v to ballast direct from battery- same no work

looked at ECU wiring. Owner swears the car started and was fine before. everything looked ok. Yellow black to neg coil etc...

I remember green wire not being used on ECU's I've wired in, but with single ballast. This car has dual ballast and green wire is going to the ballast. So pulled the dual ballast plug and just plugged in one side to the resistor (brown?) letting the green wire just be not connected.

Car fired right up. let it warm up etc...
Put in gear, dies...every time. Like it lost it's ignition, by just putting it in gear

Put the ballast wire back on how it was, with the green wire connected to ballast again (when there was no spark before) and now car starts and drives. ??? I've gotta drive the thing home tonight and I'm not feeling totally confident :D

Anything jump out as obvious to anyone? bringing a spare ballast and ECU with me...
 
crj1968 said:
Hello
just purchased a 70 Duster with a 318. when I went to look at it it wouldn't fire. Crank crank crank. Key in run position: voltage at both sides of ballast. tried jump solenoid no go

ran 12v to ballast direct from battery- same no work

looked at ECU wiring. Owner swears the car started and was fine before. everything looked ok. Yellow black to neg coil etc...

I remember green wire not being used on ECU's I've wired in, but with single ballast. This car has dual ballast and green wire is going to the ballast. So pulled the dual ballast plug and just plugged in one side to the resistor (brown?) letting the green wire just be not connected.

Car fired right up. let it warm up etc...
Put in gear, dies...every time. Like it lost it's ignition, by just putting it in gear

Put the ballast wire back on how it was, with the green wire connected to ballast again (when there was no spark before) and now car starts and drives. ??? I've gotta drive the thing home tonight and I'm not feeling totally confident :D

Anything jump out as obvious to anyone? bringing a spare ballast and ECU with me...
Click to expand...
Pull the ecu off clean it on the fender side to make sure you have a good ground connection
 
I've never heard of a dual ballast but in the circuits I'm familiar with, the ballast is bypassed during cranking to give a hotter spark and when you go to run with the key, voltage is reduced to the ignition to help save the points. So I'll be sure to follow others replies to this because the shifting into drive and it quits has me baffled as well.
 
1970 didn't come with a electronic ignition.
Somone converted it and used a dual ballast - possibly because it was an early conversion.
On the early ECU's the 5 Ohm ballast regulates power for the ECU, and the 1/2 ohm resistor does pretty the same as the .6 - .8 ohm reistor on the points ignition (controls votlage and current to coil).

Hard to comment on specific wire colors.

Only green wire on the factory is for the field.
upload_2022-5-9_12-34-57.png
 
Mattax said:
1970 didn't come with a electronic ignition.
Somone converted it and used a dual ballast - possibly because it was an early conversion.
On the early ECU's the 5 Ohm ballast regulates power for the ECU, and the 1/2 ohm resistor does pretty the same as the .6 - .8 ohm reistor on the points ignition (controls votlage and current to coil).

Hard to comment on specific wire colors.

Only green wire on the factory is for the field.
View attachment 1715924793
Click to expand...

Right the electronic ignition was put in by previous owner. I believe he took everything from a 75ish Valiant and swapped it in, which is why the dual ballast.

74 360 I will ground the ECU for sure.... the strange thing is the car dying in gear and then when I put everything back it magically worked...
what about putting the car in gear would change anything as far as ignition is concerned? Nothing
 
Different ECU pigtails have different colors.
Import thing is the pin position on the pentegon shaped connector.
With an ECU that uses only 4 pins. Top is power. Connect to the run side of the ballast.

upload_2022-5-9_12-38-3.png
 
OK a factory 73 with dual ballast resitors would be like this:
Ballast resistors are jumpered together on the run side, seperate on the start side.
Green and red wire connect the corner pin on the ECU to the 5 ohm resistor.
upload_2022-5-9_12-42-51.png
 
Mattax said:
Different ECU pigtails have different colors.
Import thing is the pin position on the pentegon shaped connector.
With an ECU that uses only 4 pins. Top is power. Connect to the run side of the ballast.

View attachment 1715924795
Click to expand...

Thanks yeah- that is how it is connected. That is how it was connected. It wasn't sparking until I took off the green/red stiped ECU wire from ballast. but then died in gear. Like everytime

I put the green/red back on and everything is fine starts right up. goes in gear ..drives down the road. strange indeed.
 
crj1968 said:
Right the electronic ignition was put in by previous owner. I believe he took everything from a 75ish Valiant and swapped it in, which is why the dual ballast.

74 360 I will ground the ECU for sure.... the strange thing is the car dying in gear and then when I put everything back it magically worked...
what about putting the car in gear would change anything as far as ignition is concerned? Nothing[/QUOTE

Is it a column shift? I wonder if the ignition switch had been recently replaced and the wires were not fed through the column properly...getting rubbed/shorted when put in drive?
Click to expand...
 
Mattax said:
OK a factory 73 with dual ballast resitors would be like this:
Ballast resistors are jumpered together on the run side, seperate on the start side.
Green and red wire connect the corner pin on the ECU to the 5 ohm resistor.
View attachment 1715924796
Click to expand...

yes thanks! That's how it is wired and how it was wired. I guess we'll see what happens when I go get it. Thanks for the lightning fast responses all !
 
crj1968 said:
yes thanks! That's how it is wired and how it was wired. I guess we'll see what happens when I go get it. Thanks for the lightning fast responses all !
Click to expand...
When you get a chance, look over the connectors - maybe something with the terminals not well crimped or ???
I say that because its the one thing you moved around a bit.
 
I thought that same thing as well. it's re-attaching the green wire to ballast that has me stumped. pretty weird
 
Mattax said:
When you get a chance, look over the connectors - maybe something with the terminals not well crimped or ???
I say that because its the one thing you moved around a bit.
Click to expand...

For sure! It was just weird because I was all proud of myself to get it running - and then dying going into gear was bizarro
 
I have an HEI setup in my other car--- maybe I'll bring that with me too ha!
 
I would just rewire it on the spot before taking it home. Its only a few wires and that way you can be sure its wired correctly. Bring a spare ECU with you also. But yes, check the ground. I like to run a ground wire right to the ECU mounting tab.
 
When you start talking wire colors, "things go wrong" because the colors are not always the same

Be certain the ballast, which is just two DIFFERENT value resistors, in one "box" --be sure that it is connected so the correct resistor is in the correct circuits. This is "coded" by the "open U" cutout in the ceramic block at one end.

Also as time goes on, it gets more and more UNlikely that you NEED a dual ballast, because if the "old style" (5 pin OEM) box has ever been replaced, it is far more likely to be (electrically) a newer 4 pin box. You can NOT tell by looking as some 4 pin boxes have 5 physical pins. You can only know by "trying" it or by carefully making resistance checks to the 5th pin to determine if it is open (infinity) to the other pins / case.

Make CERTAIN the case is grounded, and "work" the dist pickup connector in/ out several times to check for "tightness" and scrub the terminals clean

Simplified diagrams from MyMopar for 4 and 5 pin boxes. A TRUE 5 PIN BOX MUST HAVE a dual ballast, but a true 4 pin box MAY USE either a single or dual ballast

Ignition_System_4pin.jpg


Ignition_System_5pin.jpg


The wire at far top right in both diagrams marked "existing" is the "run" power feed coming from the key. THIS GOES DEAD DURING CRANKING

The power to fire the engine during cranking is not shown, but it is a (usually brown) that comes from the key "bypass" circuit (IGN2) and feeds to the ballast terminal running to the coil + terminal. This power feeds hot full battery to the coil + AND FEEDS THE BOX backwards, during cranking, through the ballast and to the box
 
Last edited:
Great info Mike and Dart273. I really appreciate the time you took to type that all out. I got the car home with really no issue… wired just like it was when it wouldn’t spark.

It does however seem to have that issue where you crank it and it fires after you kind of back off into run position. That I can fix and I’ll wire it single ballast and ground the box and see how that goes. Thanks again!
 
Putting the car in gear is "load." It doesn't take much to idle in park, but in gear it's loading the converter. Dirty plugs, weak spark, or fuel problems show up with more load.
 
Sometimes the wire inside the bal resistor breaks from fatigue. Your 'fiddling' might have re-connected the ends.
 
does the car have a neutral safety switch? i.e you can start car in neutral only

can it cut off power to igntion when in drive EVEN when car is running. due to some kind of issue with it.

Dave
 
You must log in or register to reply here.
-

Back
Top