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Unread 03-19-2010, 08:58 PM   #1
mjeckell
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1979 CJ7 
 
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Ignition Bypass Wire Help

I am a little confused. I have a 79 cj7 304. I purchased a painless wiring harness and I am trying to wire the engine compartment. What confuses me is the brown resistor bypass wire. There is a coil + wire labeled 781 brown. There is also a brown wire same size that is bundled with the starter solenoid labeled "I" term. It says that this wire is to be attached to the "I" post of the starter solenoid. I did a continuity test on both of the ends of the wires and it came out positive. It went from a 1 to a 0 on my multimeter. So I am assuming that this is the same wire. So if the "I" term brown wire goes to the "I" post then where do I put the other end of that wire I believe is wired 781 brown coil + ?????

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Unread 03-20-2010, 05:52 AM   #2
Mike Romain
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Your coil has two power feeds. One from the I terminal that sends power when the starter is turning, and the other from the key switch and resistor wire when the engine is running. This way the coil sees 12 volts when starting and 10 volts when running.
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Unread 03-20-2010, 08:26 AM   #3
mjeckell
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So my harness came all braided so I can not see all the wires and the connections that PAINLESS made. I think the brown wire marked I TERM that is bundled with the starter solenoid is the same wire that is also marked 781 COIL +. This wire travels all the way from the I TERM location back to the area close to the fuse block and then pops out with 4 wires

720 RED/White COIL +
782 GREEN COIL -
723 PURPLE TACH (will not use)
781 BROWN COIL +

This is what it says about the 720 and 781 wire in step 5

The #720 red/white wire marked “coil +”attaches to one side of the ballast resister and the remaining
length of wire attaches to the remaining terminal and goes to the “ + “ side of the ignition coil on
Motorcraft, Prestolite and standard point style ignition systems. On GM HEI ignition systems the
red/white wire attaches to the “BAT” terminal at the distributor. The Brn #781 will be used only
when a Ballast Resistor is being used. It will be installed to the starter relay on the “I” post and
goes to the coil “+” side of the coil. This is a Ballast Bypass wire to be used only when a Ballast
Resistor is being used.

In the duraspark ignition diagram it shows that this brown wire is spliced into the white wire coming from the 2 connector of the ignition module.

B. The ignition module group of wires
Motorcraft (Refer to illustration “E”)
1. The #720 red/white wire attaches to the red wire in the 2–way connector of the module.
2. The #719lt.blu wire attaches to the white wire in the 2-way connector of the module.
3. The #782 green wire attaches to the green wire in the 4-way connector of the module.

Without tearing into the loom, do you think that is the reason they sent the brown wire all the way back towards the fuse area is to splice into the 719 Lt.Blu and then I route that back directly to the COIL on the + side? There is enough wire for this.

Could I do a continuity test between the I term brown wire or the 781 brown COIL + and the Lt. blu that connects to the white wire from the ignition module. That would tell me if these are spliced right?
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Unread 03-20-2010, 08:40 AM   #4
Mike Romain
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Quote:
Originally Posted by mjeckell View Post
Could I do a continuity test between the I term brown wire or the 781 brown COIL + and the Lt. blu that connects to the white wire from the ignition module. That would tell me if these are spliced right?
No need. The blu wire has continuity to the blue wire on the S terminal of the solenoid so it gets power to the ignition module when the key is in start. This blue wire also is a different timing circuit, retarded for easy starts.

The white wire gets it's power when the key is in run and put the ignition module in normal run mode.

The brown wire just goes from the I terminal to the coil power 'after' the ballast resistor between it, the resistor and the coil power plug so the coil gets full voltage when starting. The stock one joins the coil power feed at a crimp about a foot away from the coil up in the loom and is pretty short.

I think you will need to figure how far back you need to feed the brown wire to get to that point. Maybe it can be pulled back a few feet and out the side of the loom?
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 03-20-2010, 08:58 AM   #5
mjeckell
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I checked the brown wire from the I TERM and the brown wire labeled 781 COIL + and this is the same wire. If I am understanding correctly, this wire within the loom should not be connected to any other wire.

So would it be safe to say to start removing the brown 781 wire from the loom all the way back to I TERM. Then can I hook this directly to the + side of the coil with the 720 red/white wire?
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Unread 03-20-2010, 09:03 AM   #6
Mike Romain
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Quote:
Originally Posted by mjeckell View Post
I checked the brown wire from the I TERM and the brown wire labeled 781 COIL + and this is the same wire. If I am understanding correctly, this wire within the loom should not be connected to any other wire.

So would it be safe to say to start removing the brown 781 wire from the loom all the way back to I TERM. Then can I hook this directly to the + side of the coil with the 720 red/white wire?
That is how it should work. The brown can go directly to the coil plus terminal if wanted rather than splicing it in.

Can you not just pull it out of the loom far enough to make the corner and go back out with the coil wire loom? This way it stays hidden and clean looking.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 03-20-2010, 09:12 AM   #7
mjeckell
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OK just for clarification. On the top of my coil it has two terminals. One says BAT and the other nothing. I am assuming BAT is the + side of the coil. Is this correct?
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Unread 03-20-2010, 10:46 AM   #8
Mike Romain
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Quote:
Originally Posted by mjeckell View Post
OK just for clarification. On the top of my coil it has two terminals. One says BAT and the other nothing. I am assuming BAT is the + side of the coil. Is this correct?
I would guess that also. Do you not have the old harness to compare to?
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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Unread 03-20-2010, 07:23 PM   #9
mjeckell
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Thanks for your help. I think I have it wired correctly. We will just have to wait and see once I fire it up
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Unread 04-17-2014, 03:49 PM   #10
Brown80CJ5
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I know this is an old thread, but what ever came about from sorting out the Brown #781 wire? I've run into the same problem and this thread came up in the search.
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Unread 04-18-2014, 05:07 AM   #11
Mike Romain
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Quote:
Originally Posted by Brown80CJ5 View Post
I know this is an old thread, but what ever came about from sorting out the Brown #781 wire? I've run into the same problem and this thread came up in the search.
On a later CJ, the brown resistor wire from the alternator crimps to the coil's ballast wire so it is tied to ignition power before the ballast wire to the coil +.

On earlier CJ's this brown resistor wire hooks to the alternator idiot light.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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