New (pertronix) Ignition-Coil wire: VetteVet or HEI or?

[Coley]

...I know there have been about 1329 threads working to explain and resolve this so I just felt I have to contribute on some level....lol.

Seriously tho'...I have a few questions for the experts (VetteVet, HEI, etc) but first:
-I realize that the original (resistance) wiring to the coil does not supply me with enough voltage (as is) to run my coil and thus my ignition successfully....particularly at low speed operation.
-I have thoroughly studied my trucks wiring vs. the original '72 repair manual wiring...and they seem to match pretty much bang on.
-I have a pertronix igniter ignition and (new) pertronix coil (..the 'regular' pertronix...not the igniter 3 stuff)
(refer to included pics....particularly the little yellow 20 ga. ignition wire)

Now....I know I have to run a new heavier wire according to the general information.

So, in a nutshell what I would like to know is :
1) exactly where to start this new 'heavy duty' wire...and exactly where to end it.
(all 'underhood'?...ie from the coil, down to the starter- splice...then back up to the firewall harness on the engine compartment side of things...or?)
2) The gauge range I can use to do this (min/max...ie 12 ga? 14 ga? or?)
3) Any special ends or procedures to accomplish this
4) Does any of this wiring update need to be 'in-cab' or underdash?....noting that the in cab wiring according to the manual appears to be large enough gauge.
5) Is this situation ever corrected simply by cleaning the connections?

question or comments:
-I have run several pertronix successfully for year without doing this but it appears it now is a needed upgrade for things to run properly?...go figure? or any ideas on that?
-In the underhood pics you can see where the original splice is in the two yellow (light 20 gauge) wires are...noting one runs over to the coil, then the other heads down to the starter with its upper 'reddish-purple' wire heading over to the firewall connector.
(note: I have identified the end of that wire with my finger)
IMPORTANT: I removed the original tape wrap off these wires in order to access them and show them for the pics....they will be fully retaped, etc prior to running the truck!!
-I will tape off the unused original (yellow 20ga.) wires and leave them intact in the truck for originality sake, etc.
-As well, in the pics you can see the coil connections...including my new red, heavy duty wire that I ran over to the battery (with an inline on/off switch)...this is temporary of course and was used to test out and seemingly solve the problem.
-Other 'extra' wires that show in the pics (both underhood and underdash) are probably for the tach wiring and maybe some of the underdash relates to a trailer brake, etc...this are not part of the problem at this point...they are simply part of the deal.

Ok....I'll leave off there for the moment....all input and comments are welcome.

Many, many thanks in advance guys!

Coley

[Coley]

....one more pic of the wiring on the coil.

Again, the truck is running great....but it wants this 'red' h.duty connection when its first started.......

All good
Coley

[VetteVet]

Before you do anything you need to determine if the ignition coil and the pertronix unit needs the external resistance. If they do then you will need to keep the wires to the starter and the wire from the firewall block which originates at the ignition switch on the RUN terminal. Look on the coil for the words (use with external resistor) and check the model of the pertronix and go to the pertronix website and see if you can find out if it needs the resistance.

[Coley]

....ok, will do.
Many thanks again....more to come.

Coley

[Coley]

Ok, first the 'Flame Thrower' Pertronix coil:

1) "1.5 Ohms : 8 cyl. all applications : Remove Resistor"

Now the ignition module:

2) Model 1181, GM 8 cylinder applications:
"Many vehicles came equipped with ballast resistor or resistance wire. To achieve optimum performance from the Ignitor ignition system, we recommend the removal of these components"

....also, ignitor instructions include the following:
"...To remove a resistance wire, trace the coil power wire, which was previously connected to the positive coil terminal, back to the fuse
block. Bypass this wire with a 12-gauge copper stranded wire"

Also of note in the pertronix paperwork spec sheet stuff they make reference to the pertronix working well within a voltage range of 8-16 volts......however, I am lucky to get be getting 5 volts to the coil right now as measured via the multi-meter.

Ok.....so what is the next best move....or if that last pertronix instruction is good....what is the best way/method/wire/connection or path, etc.

All good and again, many thanks!
Coley

[VetteVet]

Now that we have determined that you do not need the resistance wire or the starter jumper wire (small yellow) we only need to figure out how we are going to feed the 12 volts to the coil.

Originally Posted by Coley

...I know there have been about 1329 threads working to explain and resolve this so I just felt I have to contribute on some level....lol.

Seriously tho'...I have a few questions for the experts (VetteVet, HEI, etc) but first:
-I realize that the original (resistance) wiring to the coil does not supply me with enough voltage (as is) to run my coil and thus my ignition successfully....particularly at low speed operation.
-I have thoroughly studied my trucks wiring vs. the original '72 repair manual wiring...and they seem to match pretty much bang on.
-I have a pertronix igniter ignition and (new) pertronix coil (..the 'regular' pertronix...not the igniter 3 stuff)
(refer to included pics....particularly the little yellow 20 ga. ignition wire)

Now....I know I have to run a new heavier wire according to the general information.

So, in a nutshell what I would like to know is :
1) exactly where to start this new 'heavy duty' wire...and exactly where to end it.

There are several ways to run the wire.
1. Tie into the pink wire at the ignition switch.
2. Remove the white resistance wire from the firewall block and replace it with a 12 gauge pink or red ignition wire. You can use any color but those are common. The pink wire from the ignition switch runs to this wire on the inside of the cab.
3. Run a 12 gauge wire from the fuse panel IGN UNfused terminal directly to the coil POS terminal. Then run the negative wire from the coil to the module.


(all 'underhood'?...ie from the coil, down to the starter- splice...then back up to the firewall harness on the engine compartment side of things...or?)

No need for this step since you will be getting a full 12 volts to the coil.

2) The gauge range I can use to do this (min/max...ie 12 ga? 14 ga? or?)

I would use 12 gauge.

3) Any special ends or procedures to accomplish this

If you elect to replace the white resistance wire in the firewall block you will
need a new Packard 56 terminal to use in the block to connect the two wires.
Then an eyelet for the coil. I think NAPA carries them.

4) Does any of this wiring update need to be 'in-cab' or underdash?....noting that the in cab wiring according to the manual appears to be large enough gauge.

If you go to the IGN Unfused terminal you'll need a spade terminal. If you pull the fuse panel out you can see the pink wire that goes through the firewall. Don't confuse this one with the fuse panel feed wire which is also 12 gauge pink. You don't need to pull the fuse panel unless you decide to remove the white wire and then only if the attach bolt gives you trouble coming out.


5) Is this situation ever corrected simply by cleaning the connections?

You have to have a full 12 volts to the coil and if you get less by using any of the methods I describe then you might need to clean the fuse panel terminals and the fuse holders which you should do anyhow. The firewall block terminals are sealed but they still can get corroded.

question or comments:
-I have run several pertronix successfully for year without doing this but it appears it now is a needed upgrade for things to run properly?...go figure? or any ideas on that?
-In the underhood pics you can see where the original splice is in the two yellow (light 20 gauge) wires are...noting one runs over to the coil, then the other heads down to the starter with its upper 'reddish-purple' wire heading over to the firewall connector.
(note: I have identified the end of that wire with my finger)
IMPORTANT: I removed the original tape wrap off these wires in order to access them and show them for the pics....they will be fully retaped, etc prior to running the truck!

-I will tape off the unused original (yellow 20ga.) wires and leave them intact in the truck for originality sake, etc.
-As well, in the pics you can see the coil connections...including my new red, heavy duty wire that I ran over to the battery (with an inline on/off switch)...this is temporary of course and was used to test out and seemingly solve the problem.

You won't need this when you wire the coil with one of the methods above.

-Other 'extra' wires that show in the pics (both underhood and underdash) are probably for the tach wiring and maybe some of the underdash relates to a trailer brake, etc...this are not part of the problem at this point...they are simply part of the deal.

Ok....I'll leave off there for the moment....all input and comments are welcome.

Many, many thanks in advance guys!

Coley

[Coley]

Ok...I think we have it resolved.

Quick recap....I was lucky to be getting 5 volts (or slightly) less across the coil, which clearly was not popular with my pertronix unit wanting to fire all cylinders at idle....or when cold.
When I increased the rpm and spun the alternator up, and I assume the output voltage,...it got better.

Regardless, I ran a new wire from the fuse box (ignition unfused) and followed the existing little yellow (20ga?) coil/ignition wire route out through the firewall and along the upper tray and then back to the coil and connected that onto the positive side of the coil, just like the original.
It is now showing about 9+ volts across the coil at this point....and the pertronix, the coil and the truck seems to be pretty happy about that.
The existing/original little yellow coil wire has been disconnected, taped off and set aside near the coil for future use or reference, but its still fully intact otherwise.

Hopped in the truck and it started up like new....

Plus, having also found a problem within the carb with the float/seat connection wire coming off....they were a couple of interesting low budget problems that can really be a downer if left unchecked and they can certainly make a vehicle tough to enjoy.

All good!...and importantly, I learned some more interesting electrical stuff about the truck and its ignition system.

The only thing not fully known...is why the coil supply voltage went from working and supplying the pertronix with enough voltage....to it not supplying the pertronix with enough voltage?
...maybe something in a connection somewhere?...or the ignition switch itself?...or maybe down on the starter solenoid?...dash/firewall bulkhead harness connector?....or?
I'm still curious about this.

all Good
Coley

[vince1]

The Petronix conversion I did to a car reads 14+ V at the coil with it running.
Is not 9 V too low?

[Coley]

Actually, I think there are 2 different voltages that apply to these ignitions.
One is the voltage that is supplied 'up to' the coil, as you mentioned.
The other is the voltage 'across' the coil...which is lower due to internal resistance.
Either way, Pertronix states that their units will run well on a voltage range of 8 to 16 volts....and I am within that now.
Previously I was down just below 5 volts (without the alternator adding voltage)...and that was what caused 'cut out' at low speed.

The update tho'....right now, ba-da-bing, starts up great in the morning...2-3 pumps on the gas, starts right up and goes to choke/high idle....I head out within about 20-30 secs.

Overall tho'....its a great exercise to go thru not only in terms of some interesting troubleshooting work...but also the great insight and learning curve that comes from knowing more about your engine, particularly the electrical/ignition side of things.
Always comes in handy at some point.....often in helping someone else out of a similar situation.

All good
Coley