Need some help with wiring a 304. - JeepForum.com
 
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post #1 of 3 Old 08-29-2008, 10:26 AM Thread Starter
_Lou_
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Need some help with wiring a 304.

First let me start by stating I am no electrician. I am a booger eating, mouth breather when it comes to engine and electrical wiring. So, I have a 1980 CJ7 with a 304. I have recently replaced the entire wiring harness with a painless harness. I have also replaced the ignition module with a OEM replacement module, I have replaced the coil with a MSD Blaster 2 coil, and I have put the "Team Rush" cap and spacer on the distributor.

Now, in the instructions from Painless, it shows this schematic:



In this schematic, it shows brown wire #781 (I terminal wire) coming off the starter solenoid and dead ending at the white wire from the ignition module. This is represented by the brown wire meeting the white wire with a black dot.

Question 1: Does that mean I simply splice the brown and white wire together?

Question 2: If I do just splice those two wires together, do I continue with the brown or white wire to the "Ballast resistor"

You might also note once the brown wire and white wire are spliced on the schematic, there is an arrow pointed to this wire labeled "Resistor Bypass Wire". If you follow that wire to the ballast resistor, it has a little semi circle , is this "schematic speak" for "these two wires do not splice"?

Question 3: What is this "Resistor Bypass Wire"? I assume I need it, as it is in the schematic.

Here is a close up of the area in question:


Now on to the "Ballast resistor".


Other side:


I do not recall pulling one of these off when I tore the Jeep down, but that was five years ago. I have found a spot real close to the coil to mount the ballast resistor.

Question 4: The schematic has one terminal coming from the fuse block and then going to the Ballast resistor. The wire then continues from the Ballast Resistor to the Positive coil. You will note the Positive coil wire side also has the white (and brown?) wire attached to it as well. This confuses me. Am I supposed to splice the white (and brown?) wire to this positive coil wire? (that seems wrong to me).

Sorry for all the dumb questions, my Dad, an Auto mechanics teacher for 38 years, and partner (read: Brains) on this project died suddenly two weeks ago, so I am kinda lost.

Thanks for all your help Jeep Forum.

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post #2 of 3 Old 08-29-2008, 03:07 PM
JeepHammer
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Quote:
Originally Posted by _Lou_ View Post
First let me start by stating I am no electrician. I am a booger eating, mouth breather when it comes to engine and electrical wiring. So, I have a 1980 CJ7 with a 304. I have recently replaced the entire wiring harness with a painless harness.
'Painless' should be named 'PainInTheA$$'.

Quote:
I have also replaced the ignition module with a OEM replacement module, I have replaced the coil with a MSD Blaster 2 coil,
Most of the $30 discount store (Read: 'IMPORT') modules don't live very long, so keep that in the back of your mind if you only shelled out $30 for it.

Blaster 2 or Blaster 2F Coil?

Quote:
and I have put the "Team Rush" cap and spacer on the distributor.
Doesn't affect this wiring at all...


Quote:
In this schematic, it shows brown wire #781 (I terminal wire) coming off the starter solenoid and dead ending at the white wire from the ignition module.
That would be correct.
The '#781 Brown' wire should be a 16 Ga. and it sound come from the Starter Relay 'I' or Ignition terminal.
It powers the ignition coil with a full 12 volts when the engine is 'Cranking'.
It also powers the ignition module 'Start' circuit, which is the 'White' module wire.

Your Motorcraft/DuraSpark ignition system can be broken down into to sub-systems...
"Starting" or "Cranking", in which the module is receiving power on the 'White' wire, and is retarding the timing 8 to 12 degrees for easier starting,
And the 'Run' circuit, which the coil is power through a resistor to keep the module alive, and the module is receiving it's power through the 'Red' wire, with NO retard in the timing between trigger and firing cylinder...

This is the 'Starting' circuit of your Motorcraft/DuraSpark ignition with the 'Run' circuit excluded from the diagram as if it doesn't exist...



The power comes in from the Factory 'Blue' wire to activate the starter relay.
The starter relay powers up the 'I' terminal,
Which in turn powers up the Module and Coil so things start while the engine is cranking.

Since you are somewhat familiar with the painless diagram,
Let's try it this way...

The key switch signal to start the engine rides in on the #719 Lt. Blue wire to the starter relay, activating it.

When the starter relay activates, the 'I' terminal becomes 'HOT' and sends out power on the "#781 Brown" wire to the 'Tee' connection.
That connection powers up both the ignition coil, and the ignition module via the "RESISTOR BYPASS WIRE".

Now you ignition is 'HOT' during 'CRANKING',
And, since the module is powered up via the 'WHITE' wire, the ignition is retarded 8 to 12 degrees for easier engine starting...
..................................

Quote:
This is represented by the brown wire meeting the white wire with a black dot.
The black 'DOT' means the wire CONNECTS to that wire it 'ENDS' at.
No 'DOT', NO CONNECTION!

Quote:
Question 1: Does that mean I simply splice the brown and white wire together?
Yes.
The "DOT" means there is a solid connection at that point.
If you didn't want to cut into the wire insulation at that point, connecting the 'BROWN' wire at the resistor connector is perfectly acceptable also.

Frankly, splices in the middle of wires on an off road vehicle harness is just asking for trouble!

Quote:
Question 2: If I do just splice those two wires together, do I continue with the brown or white wire to the "Ballast resistor"
YES.
That's what is called a 'Tee' connection, for obvious reasons...

Quote:
You might also note once the brown wire and white wire are spliced on the schematic, there is an arrow pointed to this wire labeled "Resistor Bypass Wire". If you follow that wire to the ballast resistor, it has a little semi circle , is this "schematic speak" for "these two wires do not splice"?
NO,
The 'Arrow' you are seeing at the 'White Wire' denotes a connector.
----Wire 'In'--------> Connector >-----Wire 'Out'--------
Looks like this on a diagram,
---------->>----------- Or like this, --------<<---------

Quote:
Question 3: What is this "Resistor Bypass Wire"? I assume I need it, as it is in the schematic.
When in 'Normal' operation, the Motorcraft/DuraSpark ignition uses a Resistor to knock back the current to the ignition coil/module.

The 'Bypass' is a left over from breaker points days that allows a full 12 volts at full current to get to the ignition coil during starting.
Makes for a 'Hotter' spark when 'Cranking' the engine trying to get it to start on a cold, damp day.

The DuraSpark module went one better and added a 'Hot Start' retard circuit to the ignition module and hooked up to that bypass...
So when your engine is 'HOT' and as it's highest compression, the retarded timing allows the crank to roll over farther before firing the cylinder,
Making the engine MUCH easier to start when it's hot.
-----------------------

Quote:
Now on to the "Ballast resistor".
'Ballast Resistor' is a misnomer. It's just an ignition circuit resistor, there aren't multiple coils working together that need a 'Ballast' to keep them synchronized.
Again, a left over from model 'T' days...

Quote:
I do not recall pulling one of these off when I tore the Jeep down, but that was five years ago.
That's because the factory used a RESISTOR WIRE, about 45" long, and it was bundled in the factory harness.

The small ceramic resistor you have now isn't what I'd normally recommend...
These small resistors try and knock back the current to the coil in just a few inches of wire instead of 45" where the heat from that action can be dissipated over a larger area.

Those small Ceramic 'Potted' resistors fail much sooner than the factory style resistor wire, and they are much more susceptible to corrosion, water, ect. than the factory resistor wire.

REALLY hot wire gets splashed with water, it corrodes immediately at the very least, and sometimes breaks from the quick contraction...

Quote:
I have found a spot real close to the coil to mount the ballast resistor.
A lot of people mount them ON the coil bracket, keeps them handy when you have to test/replace them.

Quote:
Question 4: The schematic has one terminal coming from the fuse block and then going to the Ballast resistor.
The wire from the 'Fuse Block'
#720, 'Red' with/'White' tracer,
Would be the 'RUN' power circuit from the ignition switch...

This is EXACTLY the same diagram as above, but with the 'START' circuit edited out...
You can follow the 'RUN' circuit through the resistor to the coil and module...

[url]http://www.JunkYardGenius.com/ignition/jeep/IMAGES/ignitionrun01.gif[/img]

When you let off the key switch 'Start' or 'Crank' position, the key switch snaps back to a 'Run' position.

That wire is run through a fuse in the fuse block, the 'IGN' marked fuse.

That wire is what feeds the module a full 12 volts on the 'Red' wire
(NOTICE THE SPLICE ON THE #720 Red w/White trace that runs the module 'Red' wire?),
And feeds the ignition coil through the ignition resistor.

Quote:
The wire then continues from the Ballast Resistor to the Positive coil.
That would be correct.
#720, RED w/White trace, feeds the splice to the module 'Red' wire, then continues to the ignition Resistor to power the coil.

Quote:
You will note the Positive coil wire side also has the white (and brown?) wire attached to it as well.
At the other end, or OUTPUT of the resistor is where the ''#781 'Brown'/Resistor Bypass Wire' connects...
It 'Bypasses' the resistor, by connecting to the output terminal and therefore isn't running THOUGH the resistor,
While the #720 RED w/White trace runs THROUGH the resistor to get to the ignition coil...

What you are probably not understanding is...

The 'Bypass' and the Starter Relay 'I' terminal are 'Dead' when the ignition switch is in the 'Run' position...

Think of it this way...
Make a copy of that diagram, and ERASE the bypass, the #781 Brown wire, the starter relay, all that...
That's only there for starting and has NOTHING to do with the 'RUN' position of the key switch and the #720 RED w/White trace & Resistor circuit.

Make another copy, and erase the '#720 Red w/White trace and resistor from the circuit.
They are 'Dead' and don't come into play when you are 'Cranking the engine...

What most people miss is,
There are two entirely different circuits at work here, and they just happen to share a few connection points...
Which makes them look like they are all inter-dependent, but they aren't...


Quote:
This confuses me. Am I supposed to splice the white (and brown?) wire to this positive coil wire? (that seems wrong to me).
Once you make the copies and rub out the other half of the harness and start to understand how the 'Run' and 'Start' circuits work independently of each other, this won't be NEARLY as confusing!

Quote:
Sorry for all the dumb questions, my Dad, an Auto mechanics teacher for 38 years, and partner (read: Brains) on this project died suddenly two weeks ago, so I am kinda lost.

Thanks for all your help Jeep Forum.
Sorry to hear about your father...
So this is kind of like his legacy to you!
We will get you up and running! Tribute to your dad!
-------------------------------------

Now, this might help,
It's in the orignal factory colors, but it shows the Motorcraft distributor and DuraSpark ignition module in their native Jeep locations, and it shows the proper connectors and polarity if you are reusing that stuff...


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JeepHammer is offline  
post #3 of 3 Old 08-29-2008, 10:56 PM Thread Starter
_Lou_
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Posts: 39
Well, my living room just got brighter, because a little imaginary light bulb just illuminated above my head. Thanks again for your help JeepHammer. It makes sense about having two separate systems. I have salvaged all of the factory connectors from the original harness. I have attached them all to the ignition module, distributor and coil. Now that I look at the system and somewhat understand it, it is really quite simple....it's color coded for cripes sake. It just took me awhile to trust the fact the original colored wires from almost 30 years ago are the same colors Painless used today. Once I was okay with trusting the colors, not too bad.

That combined with your information, I feel I can get the wiring finished tomorrow.

Oh yeah, sorry, it is a Blaster 2F.

I was at NAPA today and was looking for plug wires. Of course the employee gave me the stock (non Team Rushed) plug wires. I guessed it was from an early '90's Ford F250, but he came back with plug wires that looked a little small. Do you have the part number for the correct wires to use?

Is there a part you would suggest using in place of the "Ballast Resistor"?

One more question on grounding. I have read several threads and recall you recommending grounding both heads. I have grounded the passenger side head, and picked up a second grounding strap from NAPA today. Is it better to ground each head to the respective side of the frame, or do you recommend taking a ground strap/wire from one head to the other head and then to the frame?

Thanks again.

Last edited by _Lou_; 08-29-2008 at 11:28 PM. Reason: Adding a question.
_Lou_ is offline  
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