wiring an Msd ignition

[AmadeusCharger500]

I am stumped on one point.

The engine harness has a blue wiring going to the ecu and to one side of the ballast. It then has a brown wire coming from the ballast to the coil.

There is a small red wire to be hooked from the MSD box. Instructions say to hook it to the old source for positive coil wire. Would this be the brown wire or the blue wire.
What in turn do I do with the wire that I do NOT hook the MSD box to?

Thanks,
Heath

[71_deputy]

USE THE  blue wire for 12 volts

brown- tape it out of site!

[AmadeusCharger500]

I think everything is hooked up correct. I have double checked all wiring.
Car will not spark.
This car was just running with the previous system I had hooked up. Therefore some variables can be discounted.
I checked voltage at different points with the key on position.
Should I be getting 12 volts at the coil?

I get 12 volts to the blue wire that is going into the MSD box(small red wire).
I don't get any reading from either wire coming from the box to the coil, and of course none at the coil.

[firefighter3931]

Heath, have you got the heavy red and heavy black wires hooked up to the battery ? The small red is just a trigger wire that tells the box that the ignition switch is on.

Ron

[AmadeusCharger500]

Yes, In fact I have them hooked directly to the battery. The small wire is hooked to the blue engine wire that went to the ballast. I have the ballast jumped. Its getting 12 volts to small red wire into the box. I changed coils also.

I did the trouble shooting test in the manual.
Jump the distributor wires and touch the coil to ground. Heard a pop then (I assume it sparked and I missed it), nothing after that. Perhaps the unit is faulty?
It is used from e-bay.

I just hooked up this same unit in my 2nd charger and It works like a charm. I am thinking perhaps just to swap the one I know is good and see if it works.

[71_deputy]

I THINK that the pickup has a problem or wires to the msd.

[Mefirst]

The Msd box itself will give the coil 12v.

The only wire that you connect to the brown Ignition wire (original coil + wire) is the small red wire, the wakeup wire for the Msd box. This same wire is also connected (brown) to the ballast resistor from ign. lock assebly. Then the thicker Red/Black wire are connected directly to the battery.

Then you have the distributor wires that will go directly from the box to the dist.

I dont know what box your running or what coil, distributor, but check the dist. pickup so it is good.

/Tom

[John_Kunkel]

To use the MSD you have to splice the brown wire and the blue wire together.

The blue wire will have power in the Run position but it shuts off when the key is turned to Start and only the brown wire is powered in Start. By splicing them together you will have power in both Start and Run.

[Mefirst]

To use the MSD you have to splice the brown wire and the blue wire together.

The blue wire will have power in the Run position but it shuts off when the key is turned to Start and only the brown wire is powered in Start. By splicing them together you will have power in both Start and Run.

How??? Doesn't the blue wire go to the opposite side of the ballast resistor than the brown wire??? If you splice them together you'll fry the ballast resistor??? The brown wire is the "Run" wire when as the Blue wire is the "Start".

The wake up wire (small red) from the Msd box should be connected to the original coil + wire, which at least in the 1970 is the brown wire from the ign. lock.

/Tom

[AmadeusCharger500]

Well as stated, I have my other car wired the same way and it runs fine.
I spliced the brown to the blue at the ballast. It really doesn't matter if I put the MSD box to the brown or to the blue since they are being spliced together. Those wires were in the same circuit anyway right? The ballast was the splice!
Also as stated I had this car running perfectly before changing to the MSD box. So I don't think there is anything wrong with the distributor or coil (which I tried changing anyway)

[Mefirst]

Well if you know you wired it right, the dist and coil are ok, well the only thing left is that the MSD box has crapped out. Nothing new though, I bought a brand new Digital-6 box, had to send it back cause it was broken.. -God only knows when Ill get it back..

About the wires. I dont have the wiring diagram at hand, but to what I understand the wires are not the same circuit. The blue wire is the one that lets juice to the starter when you turn the key into "start", when you let go of the key and it goes back to "run" then the brown wire will be hot. To what I understand if you splice the blue/brown wire together the starter will also be "hot" in when the key is in "run", in other words it would crank the starter as soon as you turn the key from "off" to "run"..

[AmadeusCharger500]

If I knew anything about anything I would have a sensible thing to say.
What you are saying makes sense and I would love to know what the deal is with these 2 wires (blue and brown).
All I know is JK and 71 Deputy appear to wire it this way, and I did too. One of my cars runs fine. This other one, well,  I am beginning to think its the box. I might know better tomorrow when I try swapping the other one in.

HH

[71_deputy]

taping the brown to the blue will not hurt.

the brown wire is a 12 volt feed to over ride the ballast resister on startup.
blue is hot all the time- run or start

reason... if the blue was not- then the electric chokes on the car will not work- they are powered by the blue wire.

John Mac

ps- it is the small yellow wire that provides power to turn on the starter relay.

[Mefirst]

taping the brown to the blue will not hurt.

the brown wire is a 12 volt feed to over ride the ballast resister on startup.
blue is hot all the time- run or start

reason... if the blue was not- then the electric chokes on the car will not work- they are powered by the blue wire.

John Mac

ps- it is the small yellow wire that provides power to turn on the starter relay.

OK, I see your point, when I got back home and had a chance to check the wiring diagram that the wire to the starter solenoid is the yellow one. I didint remember that without checking the diagram.

But I still don't understand why you should splice the blue/brown wire together? I just don't see the point of it? Please explane that.

Ive had major issues with the ignition system. Then again after a through out investigation the reason for the missing spark was that the magn. pick-up had crapped out. I wired the small red wake up wire for the Msd box to the brown wire (original coil pos. wire) and do get a spark. Then again cause of a battery gone bad, I didint have enough juice to get the engine to start, at least thats what I think. I bought a brand new and stronger battery today, so hopefully I´ll see a change...

Anyways, Id still want to know what benefit one would get if you splice the blue/brown wires together, than to only use the current in the brown one, like I did...

/Tom

[John_Kunkel]

the brown wire is a 12 volt feed to over ride the ballast resister on startup.
blue is hot all the time- run or start

reason... if the blue was not- then the electric chokes on the car will not work- they are powered by the blue wire.

Incorrect, the blue wire shuts off when the key is in the Start position and only the brown override wire is powered, once the key is returned to the Run position the blue wire regains power; a simple test light will show this.

Electric chokes wired to the blue wire will also lose power for the short time the starter is engaged.

[Mefirst]

the brown wire is a 12 volt feed to over ride the ballast resister on startup.
blue is hot all the time- run or start

reason... if the blue was not- then the electric chokes on the car will not work- they are powered by the blue wire.

Incorrect, the blue wire shuts off when the key is in the Start position and only the brown override wire is powered, once the key is returned to the Run position the blue wire regains power; a simple test light will show this.

Electric chokes wired to the blue wire will also lose power for the short time the starter is engaged.

OK, so why splice the two wires (blue/brown) together in the first place??? The only reason I see to doing that, is to by pass the ballast resistor al together for some reason -Why I don´t understand...

[AmadeusCharger500]

Okay now I am stumped.

Let me try to explain this as simply as possible, because I need help.

I have 2 cars.
74 charger with MSD system
71 charger with FBO system.
Both running perfectly

The original question of this post is about my 71.
I tried replacing the FBO in the 71 with a new(EBAY USED NEW)  MSD box and it did not work. "Was the box faulty" I asked.
So i changed over the MSD box from the 74 to the 71.
It did not work. (Although it started once) some weird occurance from the twilight zone, maybe I was dreaming.
So I put the other MSD (EBAY USED NEW) "supposed faulty" box into the 74.
It worked.
I have wired both cars exactly the same. Although the 74 had a dual ballast and the 71 a single.
The only thing I can think might be at fault is how I hooked up the 12volt switch source.
I have tried
1. splicing it between the two ballast wires.
2. connecting to just the blue side of the ballast.
3 Connecting it to the brown side of the ballast.

[Mefirst]

I have personally never hooked up a 4 pin ballast resistor, my setup uses a 2 pin resistor. But I don't think that there is any real difference..

One thing that comes to mind about your predicament is a ground related problem. A bad ground connection will mess up your day. You can rule out the box cause it works OK in the other car. Another thing to check is for voltage loss. What kinda coil are you using? Is the distributor cap, rotor and pickup OK?

Then again I'm no expert, Ive been battling with my cars electric system now for 6 months. Ive rewired the whole dash harness, changed out the internals in the distributor, tried out 3 different coils, "bench" tested both of the Msd ignition boxes I have (The new Digital 6 box was busted but the old AL7-2 box was OK.)

Right now my problem is that my ride has a just insane voltage drop when cranking then engine (Ign. spark is good, fuel delivery checks out good). Voltage goes from some 12.5 down to 7.8 volts, and thats well beond what is acceptable. Today I found out that the battery pos. cable betwen the starter and starter solenoid was in bad shape (again learnt that one should never reuse old stuff, the cable in question was badly soldered to the connector, the work of a previous owner). So my guess is that the problem with the voltage loss may be cause of this bad battery cable. Then again I'm not shore about anything anymore, had so many gremlins already #### up my day, so wouldn't be surprised if I find something else, once I mounted a new battery pos. cable... Then again this is not everything, my bad luck also seems to hold its grip on me, the brand new battery I bought was crap as well, so need to take it back to the shop where I bought it from...

..then you always have people telling you to go back to the stock ignition system, but I don't think a stock setup would make my life any more simple than with the Msd setup. If your electrical system doesn't work, you have to find the bugs and sort them out, changing to another type of ex. ignition system wont clear the bugs out, the only way to do it, is to check one wire at a time, until everything checks out...

/Tom

Ps. Sorry for the rant...

[John_Kunkel]

OK, so why splice the two wires (blue/brown) together in the first place??? The only reason I see to doing that, is to by pass the ballast resistor al together for some reason -Why I don´t understand...

Here's how it works.

When you first turn the key to Run the blue wire is powered but the brown wire isn't. When the key is turned to Start the blue wire shuts off and the brown wire is powered (Mopar's idea, not mine). The brown wire is powered in Start in order to bypass the ballast resistor and shoot straight battery voltage to the coil to give a hotter spark for starting. When the key is returned to Run the brown wire shuts off and the blue wire powers the ignition through the ballast.

When wiring a MSD and eliminating the ballast, the brown and blue wire must be spliced together in order to insure there is power in both Start and Run. If only the blue wire is used to power the MSD there will be no power in the Start position.

[AmadeusCharger500]

Thanks again John, you are always very helpful.

I got the thing running.
I think it is just having a hard time starting now. Perhaps it has been flooded from me messine with it so much.

Next item of this.
Do I have to redo the timing? It sure doesn't seem to run the same.

[dodge freak]

Hi I new but have been reading this site for a while. When I seen you are having a problem with you msd I thought I might be able to help. Make sure the pick up leads from the dist. are not backwards, this will cause your timing to be wrong. You should not have to touch your timing to get it to run OK. Afterwards you may want to  fine tune it a very small amount. I went to a 7 al over my 6al last year and that happen to me but it idle ok but lost power the more you rev  it. BTW everybody said it wont make it run any better over the 6 unit but it did to.Engine will now idle ice cold first time I start it even if its over a week, maybe my unit was old and weak don't know but I would just use the 7 al from now on unless you have to use the 6 in your state. Live in Michigan and nobody ever looks at your cars here. Good Luck I hope thats it. Just swicth the wires around and see if it runs good.You should not hurt any thing.

[71_deputy]

I stand corrected!!!!!!!!!!!!  blue wire will have no power on start!!!!  brown wire will!!!!

you must splice both wires together to feed a GOOD 12 volts to the msd unit.

went and checked some ing switches and found above true.

reason for me to say the other way was that the existing ballast resistor was back feeding power to the blue wire.

now the reason that some msd's will work buy not using the brown wire is that it still is getting power- though low- thru the ballast resistor.
if you remove the ballast then you have to splice the two together!!!!

John Mac  my 

[Mefirst]

How did you guys wire it ?? Like where did you make the splice, before or after the ballast resistor ?

Another thing I would want to know is what importance does the ballast resistor play cause one of the alternator Fld wires are connected to it. So if you loose the ballast resistor al together what would happen ?

/Tom

[dodge freak]

Ballast resistor? My car has not had one scine I got it home and put on a msd on it 10 years ago. That went right in the junk pile  right after that lean burn ignition system and vacuum advance on the dist.  Maybe you should call msd tech line they do have some good guys there, but I have gotten the run around too. Like change your coil , make sure you have at least 12 volts, make sure your spark plugs wires are perfect,  before they get it right. Not sure if they just want to sell you more stuff or just some guys are better than others. Every time you call you get a different guy. But they are ok I think phone # is 915-855-7123 monday-friday 7 am-6 pm MST.

[Mefirst]

I reread this thread over again.. and I still don´t understand why you would bypass the ballast resistor. The thing that makes me most confused is that one of the FLD wires from the alternator is also connected through the voltage regulator to the ballast resistor (blue wire side). If you remove the ballast resistor, where do you connect this wire then??? and how will that effect the function of the cars electric system..

I just don´t buy this way of wiring up and MSD box. If this was the way to wire the box, MSD would have put it in print in the user manual for the ign. box. But al it states is to take power to the "little red" wire from the original coil + wire, which in the Mopar electric system is the brown wire, NOT the blue..

Id like some closure to this and you guys who wired your car by splicing the blue/brown please explane why and what the benefit would be to wire it up like that, an further where did you make the splice between the wires and did you loose the ballast resistor al together...

/Tom