# Purple ignition wire. Not hot



## Johnnygoat (May 24, 2021)

Changed my steering box and didn’t connect the column. Didn’t feel like taking it back off so I loosened the column and slid it back to be able to get it on the studs. Since then I can’t get power at the coil. Changed ignition switch and cleaned connections at column . If I connect direct to battery I can drive it. I was told it could be the voltage regulator. They are cheap so I will change it but any suggestions would be helpful. I have a switch under the hood but I would like to fix it Thanks!


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## PontiacJim (Dec 29, 2012)

And that was a 1948 GTO? Has the double reverser forward step shifter option?


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## BLK69JUDGE (Jun 10, 2010)

Welcome to the forum Johnny G

Jim the 1948 GTO/s didnt have purple wires ... they were still cloth covered ..and 6 volt ...
so any way
looks like you have a 70 in your picture
are you working on that car ?
so the car cranks over but WONT start ...so you added a jumper wire from the + battery to the +coil to make it start
AND
you need to unhook the wire to shut it off ... now ?? is that correct ??

and

the purple wire is power to the solenoid to turn the car over NOT power to coil


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## Autie1969GTO (Mar 5, 2019)

PontiacJim said:


> And that was a 1948 GTO? Has the double reverser forward step shifter option?


You crack me up


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## Jetzster (Jan 18, 2020)

Good one Jim😝


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## PontiacJim (Dec 29, 2012)

BLK69JUDGE said:


> Welcome to the forum Johnny G
> 
> Jim the 1948 GTO/s didnt have purple wires ... they were still cloth covered ..and 6 volt ...
> so any way
> ...


So true, I have the cloth covered wiring on the '48 International I am working on which I replaced with a new repro cloth covered wiring harness. Converted the 6 volt positive ground over to a 12V negative ground system for easier maintenance and parts replacement.

No double reverser forward step shifter option option. My 1946 Studillac cab-over single axle tractor that had the Allison V-16 and double over 15 speed transmissions butted front to back to give me top end unlimited and had the double reverser forward step shifter that I fabricated for it out on the farm. Only problem was that I was never able to find out what top end was because when I hit about 180 MPH with the bias-ply 20" tires they had back then, they would get so hot that rubber would start chunking off in big pieces so I would have to back out of it. Maybe you saw the truck in the June 1947 edition of *Custom Speed Trucker*? On paper, the slide rule engineers calculated I could do around 257 MPH on the top end - and this was waaaaay before Don Garlits ever hit his 200 MPH goal and shaved off his beard. Heck, if he wanted to shave off that beard because he hit 200 MPH, I could have done it for him if he had just stuck his head out of the dragster seat when I blew by him at 257 MPH - I'd 'ave given him a clean shave he would have never forgotten.


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## LATECH (Jul 18, 2018)

Coil does not power up from a purple wire. The starter on the other hand energizes with a purple wire.


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## Johnnygoat (May 24, 2021)

BLK69JUDGE said:


> Welcome to the forum Johnny G
> 
> Jim the 1948 GTO/s didnt have purple wires ... they were still cloth covered ..and 6 volt ...
> so any way
> ...


I just changed engine harness ra lll. 70 judge. Starts but only when cranking. 1948 GTOS ARE FAKE. BEWARE. ESPECIALLY JUGDES. The positive coil wire seems to only have power when cranking. Pink/ black. I guess the problem is inside. Replaced ignition switch and cleaned large plugs on column. The pink / black must go to the switch. I will take my seat out again and poke around. I don’t really want to replace the inside harness. Jumping to the battery will run the car so it’s definitely not getting power in run position at coil.


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## Johnnygoat (May 24, 2021)

I am working on that car. It never broke in 30 years until I fixed it. New battery cables ,ignition switch,engine harness, I suspect it’s the column wiring


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## BLK69JUDGE (Jun 10, 2010)

have you adjusted the switch ??? it has slots in it ,,,


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## PontiacJim (Dec 29, 2012)

Johnnygoat said:


> I am working on that car. It never broke in 30 years until I fixed it. New battery cables ,ignition switch,engine harness, I suspect it’s the column wiring


As I recall, this problem has come up in the past. The '70, maybe even the '69, has a little different wiring set-up going from the ignition switch and/or to the coil. There should be 2 wires on the Positive lug on the coil - which the earlier points set-up also has, but is indeed different in how it is connected.

The Starter solenoid uses both lugs, "R" and "S". One Purple wire coming from the ignition goes to the "S" terminal and a wire attached to the "R" terminal goes up to the Positive lug on the coil. The second wire (not the once from the solenoid) found on the Positive lug on the coil is the "hot" 12V wire that keeps the engine running - just like your jumper wire. This wire also ties into the ignition switch, I believe in the "Run" position on the switch - so it should have 12V if you test it as this is your power supply wire once the engine is running, or started with the "Purple" wire when you turn your ignition switch to "Start" and crank the engine over.

What was found in a past thread was that the earlier points distributors used the resistor wire to supply 7-8 volts to the points so they do not burn out. So this system only has the "Purple" wire going to the starter solenoid only. It does not have the second wire on the solenoid lug - it is unused. On the points distributor, the coil gets a full 12V to the Positive lug on the coil from the ignition switch to provide a good hot start to the coil when you turn the key to "Start". Once the engine fires, the key snaps back to the "Run" position and the direct 12V is disconnected and 12V power is sent via the ignition switch and then at the firewall bulkhead, it changes and goes through the cloth covered 7-9V resistor wire and the engine continues to run until the key is turned off.

On your car, the "Purple" wire from the ignition ONLY activates the starter solenoid. The other wire on the solenoid becomes energized with 12V from the battery once the solenoid engages the starter and the engine cranks. That 12V wire then sends its voltage to the Positive lug on the coil and the engine fires up. _The minute you let off the key_ and it snaps back to the "Run" position, that 12V wire no longer carries any voltage to the coil and _the engine stops running_. This is proven when you connected a 12V jumper wire to the coil and the engine continued to run. This wire from the starter solenoid acts in the same way the 12V wire works off the ignition switch with a points set-up - except the later model cars like yours use the lug off the starter solenoid and not the ignition switch.

You then have a wire from your ignition switch that provided 12V when the key is in the "Run" position just like the points set-up EXCEPT you do not have the resistor wire, you have a regular non-resistor wire that handles 12V.

We went through this as the question came up about coils as they have different resistance ratings and we were trying to figure out why. With the '69/70 up cars, and no resistor wire, the coil provided the additional resistance. Now some cars may have had a ballast resistor block mounted on the firewall like a Chrysler product does - this I am not sure about, but have never seen one on a Pontiac that I am aware of.

Your starting wire also goes through a Neutral Safety switch and I am assuming it is working because you can crank the engine.

So that should explain things. A wiring diagram would further show you the set-up for your car. Get one.


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## Johnnygoat (May 24, 2021)

PontiacJim said:


> As I recall, this problem has come up in the past. The '70, maybe even the '69, has a little different wiring set-up going from the ignition switch and/or to the coil. There should be 2 wires on the Positive lug on the coil - which the earlier points set-up also has, but is indeed different in how it is connected.
> 
> The Starter solenoid uses both lugs, "R" and "S". One Purple wire coming from the ignition goes to the "S" terminal and a wire attached to the "R" terminal goes up to the Positive lug on the coil. The second wire (not the once from the solenoid) found on the Positive lug on the coil is the "hot" 12V wire that keeps the engine running - just like your jumper wire. This wire also ties into the ignition switch, I believe in the "Run" position on the switch - so it should have 12V if you test it as this is your power supply wire once the engine is running, or started with the "Purple" wire when you turn your ignition switch to "Start" and crank the engine over.
> 
> ...


I have a wiring diagram. I also have Petronix. I understand what you’re saying. I believe it has something to do with the ignition switch wiring. I have several ignition switches with pins in different areas and installed a ‘71 or ‘72 tilt column The wires are not in the plastic plugs because their position changed. I suspect one came loose. My question


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## PontiacJim (Dec 29, 2012)

Johnnygoat said:


> I have a wiring diagram. I also have Petronix. I understand what you’re saying. I believe it has something to do with the ignition switch wiring. I have several ignition switches with pins in different areas and installed a ‘71 or ‘72 tilt column The wires are not in the plastic plugs because their position changed. I suspect one came loose. My question


Then I think you will have to first draw a schematic representation of your the key switch you are using. Then with an Ohm meter, identify what lugs on the back of the switch are activated in the assorted key positions of "Start", "Run", and "Accessory." I don't know if you can ID the key positions from the connector at the base of the steering column? '68 and earlier use the key switch on the dash and is a little different on tracing wiring.

Next I would identify the wiring in the plug end of the wiringn harness that would normally hook-up/plug into the key switch - again assume at the lower steering column?

Look at the '70 wiring diagram and you will see the wires I noted. Nothing should change in using the Pertronix - it needs 12V to work. You still need the "Purple" wire to the starter to crank the engine. You can still use the second wire coming off the starter solenoid lug to fire the engine - gets hooked to the + Coil side. Then you still want a 12V power supply wire that will work off of your ignition switch to keep the engine running in the "Start" position. So nothing should be any different from the '70 wiring diagram.

Your other option is to find a wire/circuit that becomes "live" with 12V with the key in the "Run" position and loses its 12V power when you turn the key "Off". You would still use the wire coming off the starter solenoid for use in the "Start" position of your key. This would eliminate the need to trace a wire off your key switch that goes to the +Coil side.

You could also hook-up a hidden switch that you have to manually turn on/off and connect it to a 12V source, run it through the switch, and then to the +Coil side - which is the same as your jumper wire. I would incorporate an in-line fuse if I went that route. You would not need the wire coming off the starter solenoid, just turn the key to "Start," and with the engine spinning over, flip the switch and the 12V will light up the coil and the engine will fire up and run - let the key snap back to the "Run" position the second the engine fires up so the starter will disengage.


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## BLK69JUDGE (Jun 10, 2010)




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## Johnnygoat (May 24, 2021)

Johnnygoat said:


> I have a wiring diagram. I also have Petronix. I understand what you’re saying. I believe it has something to do with the ignition switch wiring. I have several ignition switches with pins in different areas and installed a ‘71 or ‘72 tilt column The wires are not in the plastic plugs because their position changed. I suspect one came loose. My question is what wire is the hot to coil? I am going to Wisconsin for the nationals and don’t want any problems.





PontiacJim said:


> Then I think you will have to first draw a schematic representation of your the key switch you are using. Then with an Ohm meter, identify what lugs on the back of the switch are activated in the assorted key positions of "Start", "Run", and "Accessory." I don't know if you can ID the key positions from the connector at the base of the steering column? '68 and earlier use the key switch on the dash and is a little different on tracing wiring.
> 
> Next I would identify the wiring in the plug end of the wiringn harness that would normally hook-up/plug into the key switch - again assume at the lower steering column?
> 
> ...


The problem is inside. I took apart my other 70 and the wires are in different locations but I think the rows are operated by switch position so as long as they are in the row the order might not matter. I did replace the engine harness so it’s got to be an out of place wire or a break. Maybe someone can identify which prong is for ignition / run position? I would like to use my new harness so I need to know which wire is the “ run”. It will start for a second when I stop cranking so I believe the starter wires are working properly. Another problem is I have a tilt from a 71 or 2 and when I installed it 30 years ago I remember a similar problem. I took apart a70 lemans and removed the wires ( from the clear plug) and found one out of place. I since replaced the switch An interesting thing is the ignition switch for the other car is upside down ( the mounting screws are on the opposite side. I have several ignition switches and the prongs are different. I believe they can all work if I find where the wires go. The GTO manual even has wires in a different place than my other 70 that stlll has its plug intact. Getting closer


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## BLK69JUDGE (Jun 10, 2010)

tilt and std column switches are NOT the same
the rod pulls inside the switch on a tilt
the rod pushes inside the switch on a non tilt
and yes there are variants of each that fit on the column but are NOT for our PONTIACS as wires and contacts move on the switch/plug


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## Johnnygoat (May 24, 2021)

I will do it as a last resort. Any idea on the generator light being on when jumping the coil? Even if it’s ok ,an idiot light staying on while traveling long distance can make you uneasy. Thanks for the help, I now know more than I wanted about one wire.


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## BLK69JUDGE (Jun 10, 2010)

""I will do it as a last resort. "" ???

generator light is on because your coil has jumped power !! just like leaving the key in run position with engine off
you can fry your points leaving the power hooked up and the engine not spinning..


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## Johnnygoat (May 24, 2021)

BLK69JUDGE said:


> ""I will do it as a last resort. "" ???
> 
> generator light is on because your coil has jumped power !! just like leaving the key in run position with engine off
> you can fry your points ...


I have petronix so I can’t fry points. Do you know what color the coil wire is? I know I probably have to bench check the switch which I have procrastinated. The pink/ black wire goes into the bulkhead. What color wire leads to the ignition switch? It’s a new switch but it seems sluggish on positioning. Also, is the red wire supplying power to the switch? There seems to be 3 wires hot but it’s hard to work under the dash without grounding the switch. I plan on removing it but need to know how to energize it on the bench.


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## BLK69JUDGE (Jun 10, 2010)

I missed/didnt see the " I have pertronix " part sorry

you need to slow down and do 1 thing at a time ,,, I dont know how your going to or why "bench" test the switch
new inexpensive repop switches are tight and often dont like to return to run after being in the cranking position and can click real loud and you can feel it in the key ,.,, when turning off the engine or going into accessory 

Im not getting any answers to my questions so Im out of this conversation';'''',,,.......>>>>>>>>

Scott


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## Johnnygoat (May 24, 2021)

BLK69JUDGE said:


> I missed/didnt see the " I have pertronix " part sorry
> 
> you need to slow down and do 1 thing at a time ,,, I dont know how your going to or why "bench" test the switch
> new inexpensive repop switches are tight and often dont like to return to run after being in the cranking position and can click real loud and you can feel it in the key ,.,, when turning off the engine or going into accessory
> ...


I’m sorry but I am not into the internet thing and busy with everything else. I guess it helps to be in reality. I’m one person and it’s tough to fix something that makes no sense. I changed the switch. I adjusted the switch. I changed my engine harness.I unplugged wires and took off the switch from my other GTO and checked wire positions. I want to know which wire is for the hot on the coil. ( pink black. I am going to mess with it now but only for an hour. It’s a strange problem that will eventually be resolved. I don’t really know why since I was working under the hood


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## BearGFR (Aug 25, 2008)

Dunno about 70 , but my 69 only has a single wire going to the coil. There are two outputs from the ignition switch though, one for "start" (which does not go through the resistor wire) and one for "run" which does. Those two connect to the common wire that feeds the coil "somewhere" between the switch and the feed end of that wire.

If you have power when cranking, but not when running, the problem has to be somewhere between the switch and the "coil" wire. Could be the switch itself, or the adjustment thereof, or a disconnected "run" wire.

Bear


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## Johnnygoat (May 24, 2021)

BearGFR said:


> Dunno about 70 , but my 69 only has a single wire going to the coil. There are two outputs from the ignition switch though, one for "start" (which does not go through the resistor wire) and one for "run" which does. Those two connect to the common wire that feeds the coil "somewhere" between the switch and the feed end of that wire.
> 
> If you have power when cranking, but not when running, the problem has to be somewhere between the switch and the "coil" wire. Could be the switch itself, or the adjustment thereof, or a disconnected "run" wire.
> 
> Bear


New switch. Does anyone know color and position on switch?


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## O52 (Jan 27, 2019)

69 and 70 are wired the same but the firewall plug is slightly different

Just read and responded to something similar in the PY forums.






69 gto won't start cold - PY Online Forums - Bringing the Pontiac Hobby Together


69 gto won't start cold Pontiac - Street



forums.maxperformanceinc.com




Post # 9/15

Lots of other good information included.
Problem was resolved, bad coil.


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## PontiacJim (Dec 29, 2012)

Johnnygoat said:


> I’m sorry but I am not into the internet thing and busy with everything else. I guess it helps to be in reality. I’m one person and it’s tough to fix something that makes no sense. I changed the switch. I adjusted the switch. I changed my engine harness.I unplugged wires and took off the switch from my other GTO and checked wire positions. I want to know which wire is for the hot on the coil. ( pink black. I am going to mess with it now but only for an hour. It’s a strange problem that will eventually be resolved. I don’t really know why since I was working under the hood


Find someone who is into the internet thing and order a color/laminated wiring diagram. Not expensive and it should help trace wiring as opposed to the B/W shop manual wiring diagram.









Pontiac GTO - LeMans - & Tempest


All diagrams include the complete basic car (interior and exterior lights, engine bay, starter, ignition and charging systems, dash, under dash harness, rear clip, etc). All diagrams use factory colors including tracers when applicable. All diagrams are laminated in plastic for ease of use and...




www.classiccarwiring.com





Next you should have an Ohm/Voltage meter to test for continuity (ie broken wires/grounding) and power (12V).

Some of these wiring issues can take time and may involve testing each wire/plug at a time to isolate the issue. Had a '70 GTO that would not charge and took 3 months and me finally tearing into the wiring to find that a wire had been broken inside a perfectly appearing wire casing - ie not crushed or any signs of wear. Replace the wire and the charging system did what it was supposed to. In the meantime, I did like most, VR, Alt, Bat, Solenoid, cables, etc. thinking I will get it eventually.

Dig in, start from one end of the wiring to the other and leave no wire unturned. Write down all you do, make diagrams, and test, test, test. If all else fails, drop it off at a reputable shop.


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## Johnnygoat (May 24, 2021)

PontiacJim said:


> Find someone who is into the internet thing and order a color/laminated wiring diagram. Not expensive and it should help trace wiring as opposed to the B/W shop manual wiring diagram.
> 
> 
> 
> ...


I appreciate the help. Thanks. I’ll post when it’s solved


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## PontiacJim (Dec 29, 2012)

Johnnygoat said:


> I appreciate the help. Thanks. I’ll post when it’s solved



You will get it, but it can be a real pain in the butt sometimes. I like to think of the money I am saving by doing it myself and not taking it to someone who charges $200.00 and hour and then when you get it back, the problem is fixed, but it seems a new one was created.


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