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10-06-2009, 07:23 PM
|  | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
| |  MSD 6 Hookup
Hopefully I'll be hooking up an MSD 6 shortly and I want to make sure I understand what I've read.
This will be going on an 84 w/258, Nutter Bypassed, TFI, Stealth HEI, Duraspark Distributor
I'll be using the MSD 8874 coil harness so I won't have to cut any wires.
After connected, the harness only uses 1 wire from my existing harness - right? The red coil wire (since the green wire will be disconnected at the ignition module that is no longer used).
Nothing in the instructions mentions a connection to the distributor. I had already ordered harness that will connect the MSD 6 to my distributor. This is the best way to go, right? 
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10-06-2009, 11:43 PM
|  | Addict | | Join Date: Mar 2009 Location: So.West Indiana
Posts: 435
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NOPE!
Try this, 
If you have a FACTORY TACH,
You will need a tach adapter from MSD,
If you do have a factory tach and want it to work, 
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10-07-2009, 06:23 AM
| | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
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Looks like the difference in your diagram and the msd diagram is the msd diagram uses the white wire in the harness where yours does not. Correct?
I used the (yours?) diagram below many moons ago to hook up my stealth hei. When I hook up the small red wire from the msd do I need to remove the 10ga wire I have bridged between the coil and solenoid or does it make any difference? 
And just to make things confusing, I have one of those old factory Jeep column mount tachs - 4 wire (red/red-white/orange/black). If I remember the power runs through these. Is there a way to hook this up? Is that what the tach diagram is showing or is that for a different style tach?
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Last edited by 84_CJ7; 10-07-2009 at 07:42 AM.
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10-07-2009, 08:00 AM
| | Old Hand | | Join Date: Mar 2003 Location: Fairbanks, Alaska
Posts: 642
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Hopefully this will help.
Your MSD needs 4 things to work properly.
The first is power, that is the heavy Red and Black wires.
The second is to know when to stop making spark and let the engine shut off. That is the small red wire. When it sees about 12 volts it tells the MSD to spark, when it sees about 0 it tells it to stop.
The third is the connections to the coil to actually make the spark. That is the small Orange and Black wires.
These are common to all methods of setting up an MSD. The connections might go through different plugs in different groupings but the actual electrical connections are as above.
The last thing the MSD needs to know is exactly when to fire so that it is in proper orientation to the engine. Here there are two options.
It can look for a floating (ie not connected to anything) of the white wire as would happen when the points open on an older distributor, or when the stock ignition module effectively does the same thing. This is the wiring option you show in your first post. This will work, the problem is that for the MSD to work both it and the stock ignition module must function.
Fortunately, the MSD includes another method. It can read the pulses put out by the magnetic pickup in most modern distributors (green and Purple wire) and use them directly to know when to fire. This cuts the stock ignition module out of the loop so you have one less thing to go wrong, and if you keep the stock ignition module installed but not wired in you have a built in backup for the MSD. If it ever fails, you swap 2 plugs and you are good to go.
MSD was very smart in how the made these and it is simply a mater of wiring correctly and it will know what wires to listen to and which to ignore.
The only detail is that you do not attach the wires you do not use to anything. Just tape them over and let them float, voltage wise.
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Last edited by bandhmo2; 10-07-2009 at 08:05 AM.
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10-07-2009, 08:57 AM
| | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
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Thanks. It makes good sense.
The 10 ga jumper wire was put in place to insure the coil received full voltage.
Since the MSD only uses the red coil wire for an on/off signal the jumper is no longer needed - but would it hurt anything to leave it in place? I can't see where it would but I've been wrong before.
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10-07-2009, 10:26 AM
| | Addict | | Join Date: Mar 2009 Location: So.West Indiana
Posts: 435
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Quote:
Originally Posted by 84_CJ7  Thanks. It makes good sense.
The 10 ga jumper wire was put in place to insure the coil received full voltage.
Since the MSD only uses the red coil wire for an on/off signal the jumper is no longer needed - but would it hurt anything to leave it in place? I can't see where it would but I've been wrong before. | You can leave it in place if it's difficult to remove,
and it takes a Very Small voltage 'Signal' to turn the module 'ON'...
You don't NEED a thick wire, but a thick wire will work just the same to activate the module.
Pay attention to the diagram I posted, and you will see there are adapters and connectors made to make this fairly easy to install.
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10-07-2009, 11:53 AM
| | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
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I plan on cleaning things up and following your diagram as it's more than helpful.
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10-07-2009, 07:01 PM
| | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
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Is there any reason I shouldn't use the ignition post on the solenoid to on/off activate the MSD unit? It would be very convenient.
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10-07-2009, 11:39 PM
| | Old Hand | | Join Date: Mar 2003 Location: Fairbanks, Alaska
Posts: 642
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The ignition post on the solenoid is only hot when the engine is cranking, so no it will not work for the light red wire.
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Wilhelm
I will start using Metric only when the duodecimal system is adopted!!
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10-08-2009, 07:28 AM
| | Addict | | Join Date: Jun 2003 Location: Valdosta, Georgia
Posts: 400
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I guess this is something I never thought of before so correct me if I'm wrong.
The ignition post (I) on the solenoid gets 12v when the keyed switch is in the run position AND the crank position?
AFTER the engine is running the ignition post (I) has no more voltage?
Right or wrong?
I have been experiencing a sight delayed cranking (firing up after I released the key - not during) - and now I wonder if the solenoid has some issues? Shame on me that I never thought about it.
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Last edited by 84_CJ7; 10-08-2009 at 07:30 AM.
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