Are you ready for a real weird one? Random NO spark from a MP electronic ignition system despite numerous parts swapped around...

[MWbirdLOVER70]

I soldered in the only two wires that needed it. The harness already had the two wire plug to the distributor. The green wire is not needed for the two spade ballast resistor. That leaves a black with yellow tracer to the coil negative and the blue wire to the ignition switch.

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View attachment 1752486

I clocked the ECM to put the plug closer to the ballast resistor and routed the wires underneath for a cleaner look.

View attachment 1752485

It is still a rat’s nest but I wanted to test fire again before I wrap it up with tape.

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Then, I reached inside and….spin-spin-spin!
Son of a bitch….
I left the coil wire off! It starts up like it should. I’ll wrap it up tomorrow!

Two things here. 1) one of my wires is wired to the left side of the ballast and 2) in my quest for an original looking car I’ve never used the supplied MP ballast from the kit I bought in 1986 but rather the original ballast or type used on my 70 and other pre 70 models. Just my 2 cents

 

[MWbirdLOVER70]

I’ll check with ACE hardware fir a screw that will work.
This plug sure fits tight.

I’ve only ever had the screw in those harnesses

 

[Kern Dog]

One of my wires is wired to the left side of the ballast.

I don't know that it makes a difference. If I am wrong, I'm open to learning.

 

[Don Frelier]

I don't know that it makes a difference. If I am wrong, I'm open to learning.

Greg, you have it wired correctly according to the chrysler diagram for a 4 pin ECU.
The left side would be a lower voltage to the ECU while in the RUN position due to the drop accross the ballast resistor.
(Current flow is right to left in RUN)

But wiring to the left side would provide full voltage during starting as the BROWN wire is energized in the START position, but the voltage drops significantly anyway while cranking.
Apparently the ECU still works OK with the Chrysler recommended wiring arrangement in START but it does seem like a potential weakness in the design to me.

 

[MWbirdLOVER70]

Greg, you have it wired correctly according to the chrysler diagram for a 4 pin ECU.
The left side would be a lower voltage to the ECU while in the RUN position due to the drop accross the ballast resistor.
(Current flow is left to right in RUN)

But wiring to the left side would provide full voltage during starting as the BROWN wire is energized in the START position, but the voltage drops significantly anyway while cranking.
Apparently the ECU still works OK with the Chrysler recommended wiring arrangement in START but it does seem like a potential weakness in the design to me.

I’d have to dig up my instructions but when I bought it, it said to wire to the left side ( blue wire I believe ) Maybe a revision since then? (1986)

 

[Don Frelier]

I’d have to dig up my instructions but when I bought it, it said to wire to the left side ( blue wire I believe ) Maybe a revision since then? (1986)

Well the ballast resistor orientation could be different.
One side is the feed (usually a single blue wire, same as the voltage regulator feed) the other is usually brown (directly from start position or Ignition 2) and blue to Coil + or downstream of the ballast.
If you unplug both sides and test using the ignition switch you can determine which side is which pretty easily.

 

[padam]

One thing I did when running an orange box was install a momentary switch to run full 12v to the coil on startup. (I had bypassed my original ignition switch. )

 

[Kern Dog]

Greg, you have it wired correctly according to the chrysler diagram for a 4 pin ECU.
The left side would be a lower voltage to the ECU while in the RUN position due to the drop accross the ballast resistor.
(Current flow is left to right in RUN)

But wiring to the left side would provide full voltage during starting as the BROWN wire is energized in the START position, but the voltage drops significantly anyway while cranking.
Apparently the ECU still works OK with the Chrysler recommended wiring arrangement in START but it does seem like a potential weakness in the design to me.

What I meant earlier is that I don't see why it matters which side the wires are connected to the resistor. The way I'm looking at it, as long as there is power IN and power OUT, the orientation of the wires is irrelevant. In other words, isn't it just two routes to the same destination? Technically, the power from START and RUN still have to pass through the resistor.
The harness came this way from Evans. The brown and dark blue blue (left side of ballast) were paired together, as were the two lighter blue. (right side of ballast)
Again, if I have this wrong, I'd appreciate knowing about it. I'd rather learn than be ignorant while also being confident.

 

[toolmanmike]

What I meant earlier is that I don't see why it matters which side the wires are connected to the resistor. The way I'm looking at it, as long as there is power IN and power OUT, the orientation of the wires is irrelevant. In other words, isn't it just two routes to the same destination? Technically, the power from START and RUN still have to pass through the resistor.
The harness came this way from Evans. The brown and dark blue blue (left side of ballast) were paired together, as were the two lighter blue. (right side of ballast)
Again, if I have this wrong, I'd appreciate knowing about it. I'd rather learn than be ignorant while also being confident.

Because there is battery voltage going in and reduced voltage going out. Ballast "RESISTOR" Mopar electronic ignition does not run on battery voltage like the GM HEI system does.

 

[Kern Dog]

I get that but if the components downstream of the inputs have the correct voltage, why does it matter how the wires are routed?
They still pass through the ballast. Is the ballast a one way device?
I'm still struggling with understanding electrical systems so forgive me for being slow.
Are the wires paired together wrong?
I do understand that the power during START is supposed to bypass the resistor but I'd feel better if I knew the path that power went from the ignition switch to the spark plugs.
The brown and blue wires on the left side of the resistor just merge into the harness.
The pair of wires on the right side of the ballast have one going to the ECM and the other merging into the harness.

 

[MWbirdLOVER70]

What I meant earlier is that I don't see why it matters which side the wires are connected to the resistor. The way I'm looking at it, as long as there is power IN and power OUT, the orientation of the wires is irrelevant. In other words, isn't it just two routes to the same destination? Technically, the power from START and RUN still have to pass through the resistor.
The harness came this way from Evans. The brown and dark blue blue (left side of ballast) were paired together, as were the two lighter blue. (right side of ballast)
Again, if I have this wrong, I'd appreciate knowing about it. I'd rather learn than be ignorant while also being confident.

No looking at my stock harness they did it correct and added for the ECM harness. I agree on the ballast issue also but did it the way the instructions were pre 1986 period. Hell I was a young buck then lol and had only owned my car for 5 of its first. 11 years of her life

 

[Geoff 2]

I haven't read 330 posts.....so forgive me if what I am about to write has already been covered.

You could have a high resistance problem anywhere that supplies the ign cct. Ign switch, fuse holder clamps, connection to rear of fuse holder. Etc. When the resistance is high enough, insufficient current reaches the coil..&..no spark. Several amps are req to produce a hot enough spark. I would get a Solid State Relay that can switch 10 amps [ or more ]. Only a few $$. If you want to hide it, tie wrap it under the dash to the harness making sure the contacts do not contact metal. The SSR has 4 terminals like a conventional relay, but are polarity sensitive & marked accordingly.

This is the benefit: while the ign cct requires amps, the SSR only needs a few milli amps. The one I use for my horn only needs 28mA [ 0.028 amp ]. It would switch 'on' even with high resistance in the cct. The only downside is that the internal transistors may be wired as a Darlington Pair [ not a gay couple from Sth Carolina...] which could have an internal voltage drop of up to 1 volt. Of no consequence with a car like yours.

You could also use a common Bosch 30 amp relay; these have no internal voltage drop. Buuuut they require a lot more current [ about 0.16 amps ] to energise compared to the SSR.

If you do use a relay, use a 10amp inline fuse between the bat [+] terminal [ or alt stud ] & relay output terminal.