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Old 05/06/2018, 11:02 AM   #16
Mosesatm
 
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I already replaced the ignition switch, the solenoid, the coil, and reinstalled points. Exact same problem, so I reinstalled the Pertronix.

I'm going to open up the dash today to see if something looks wonky.

Here is a video.
https://youtu.be/riAh8HbGP1U

And another one just for fun.
https://www.youtube.com/watch?v=3qqE_WmagjY

Last edited by Mosesatm; 05/06/2018 at 11:21 AM..

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Old 05/06/2018, 11:40 AM   #17
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It sounds like from the posts you are using both a Pertronix ignitor 1 and a Pertronix coil. If so, here is something to note... there are two different coils in the Pertronix catalog. One for V8 (with a 1.5ohm internal resistor added above the stock coil internal resistance) and one specifically for a 6-cyl (with a 3ohm internal resistor added). I don't exactly see how this would explain what you are seeing but it might be useful information...

http://www.pertronix.com/docs/instru...eets/40011.pdf

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Old 05/06/2018, 12:18 PM   #18
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Quote:
Originally Posted by Mosesatm View Post
I already replaced the ignition switch, the solenoid, the coil, and reinstalled points. Exact same problem, so I reinstalled the Pertronix.

I'm going to open up the dash today to see if something looks wonky.

Here is a video.
https://youtu.be/riAh8HbGP1U

And another one just for fun.
https://www.youtube.com/watch?v=3qqE_WmagjY
One thing I noted from your video is the first time you have the key in the "run" position the voltage is around ~6.5v or so and the engine does not start. This may not be a high enough voltage for the Pertronix ignitor 1 to actually function (that may be why the voltage appears to bounce around). Since the ingnitor is electronic (vs points) it does require some minimum voltage to work (and Pertronix recommends a full 12v). The second and third time you started the engine the voltage is ~8.5v (from leftover charge? and the ignitor is happy?) and the engine starts.

The only guess I have about why the voltage actually increases when the engine is running is that (1) the alternator is boosting the voltage above 12v and also (2) the ignitor is switching on and off which (I would think) would appear as an average resistance increase of the coil (1/2 switched on, low resistance + 1/2 switched off, high resistance) over that with key in the "run" position without the engine running. That average increase in resistance would show up as a higher coil+ voltage. But this is all a guess...

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Old 05/06/2018, 01:03 PM   #19
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Since you've replaced all the usual suspects, here's a simple fix:
Simply run a jumper wire from the solenoid (small terminal, brown wire) to the + terminal of the coil. It will furnish 12V to the coil when the Ign switch is in the Run position.

This way you have the best of both worlds: 12V to the coil in the Start mode, and 12V to the coil in the Run mode. (Pertronix coils love 12V)

Neil

Last edited by franklinair; 05/06/2018 at 03:33 PM..
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Old 05/06/2018, 03:00 PM   #20
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Quote:
Originally Posted by p51 View Post
One thing I noted from your video is the first time you have the key in the "run" position the voltage is around ~6.5v or so and the engine does not start. This may not be a high enough voltage for the Pertronix ignitor 1 to actually function (that may be why the voltage appears to bounce around). Since the ingnitor is electronic (vs points) it does require some minimum voltage to work (and Pertronix recommends a full 12v). The second and third time you started the engine the voltage is ~8.5v (from leftover charge? and the ignitor is happy?) and the engine starts.

The only guess I have about why the voltage actually increases when the engine is running is that (1) the alternator is boosting the voltage above 12v and also (2) the ignitor is switching on and off which (I would think) would appear as an average resistance increase of the coil (1/2 switched on, low resistance + 1/2 switched off, high resistance) over that with key in the "run" position without the engine running. That average increase in resistance would show up as a higher coil+ voltage. But this is all a guess...
I agree the low voltage is probably the issue, but why is the voltage so low? I still think someone may have switched the resistor wire and the 12V wire.

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Old 05/06/2018, 03:02 PM   #21
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Quote:
Originally Posted by franklinair View Post
Since you've replaced all the usual suspects, here's a simple fix:
Simply run a jumper wire from the solenoid (small terminal, brown wire) to the + terminal of the coil. It will furnish 12V to the coil when the Ign switch is in the Run position.

This way toy have the best of both worlds: 12V to the coil in the Start mode, and 12V to the coil in the Run mode. (Pertronix coils love 12V)

Neil
Neil,
I tried that. Didn't work. The only way the car will start every time is to completely bypass the factory wiring.

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Old 05/06/2018, 03:35 PM   #22
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Time to break out the ohm meter and chase down the circuits?

Neil
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Old 05/06/2018, 03:45 PM   #23
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Quote:
Originally Posted by Mosesatm View Post
I agree the low voltage is probably the issue, but why is the voltage so low? I still think someone may have switched the resistor wire and the 12V wire.
OK, here's a possible theory of failure... assume the ignitor1 power line, which is also hooked to the +side of the Pertronix coil, is being supplied by the stock "resistor wire" (which is 1.5ohm for V8 and ?? for a 6cyl). When you switch to "run" (but engine is not running), current from the 12v supply passes through the resistor wire and into the coil. The coil has some natural internal resistance plus the additional internal resistor that Pertronix has added to their coil (1.5ohm for V8 and 3ohm for a 6-cyl). Regardless, the current runs through both the resistor wire plus the total resistance of the coil. This divides the voltage going to the +side of the coil which also powers the ignitor1. The net of that is that the voltage that the ignitor1 uses for its power is less than 12v (apparently it can be ~6.5v based on your video). Since the ignitor1 is electronic it requires a minimum voltage to operate (unlike points). I doubt that the 6.5v is enough. If the ignitor1 is not working it cannot switch the -side of the coil = no spark. Once you get the engine running it stays running because the alternator is boosting the voltage and (I think) the coil when it is switching has a higher "average resistance"... all of which keeps the voltage which powers the ignitor1 "high enough" = happy ignitor1 = spark

Also, I am not sure (but I can speculate) why Pertronix has a different coil for V8 (1.5ohm) vs 6-cyl (3ohm) but if the coil you have is for a V8 and the theory of failure above is correct, it makes the situation worse.

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Old 05/06/2018, 03:54 PM   #24
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Iím using the 40KV 3.0 ohm coil

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Old 05/06/2018, 05:03 PM   #25
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I just looked at the Pertronix Ignitor wiring diagram. It says to use full 12V as power to the Ignitor, so you would want to use a separate switched power source for it.

Steve

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Old 05/06/2018, 05:07 PM   #26
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Quote:
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Neil,
I tried that. Didn't work. The only way the car will start every time is to completely bypass the factory wiring.
I think bypassing the resistor wire is the way to go. It ensures that all voltages going to both the coil and the ignitor1 are to Pertronix's spec.

Either add a new wire in parallel to the resistor wire from the key switch to the +coil and ignitor1 (no need to remove the resistor wire, just disconnect it and tape off the end).

Or add an external relay that switches the 12v to the +coil and ignitor1, controlled by the existing resistor wire. I did the this when I installed my Pertronix because (1) I didn't want to dig around under the dash (2) I don't like the idea of running high amp current into the dash area (esp with all the old wiring) and (3) it was much easier for me to understand what I was adding than to completely decipher the Ford schematics

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Old 05/07/2018, 06:48 PM   #27
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Here’s an idea that may kill two birds with one stone.
What if i run a wire from the hot side of the solenoid to a fog light switch then to the coil. That would give me 12 volts for the Pertronix and it would add an extra level of security.
Will that work?

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Old 05/07/2018, 09:04 PM   #28
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That would work, but it's something else to remember to do to start or shut the car off. I also wouldn't really consider it an extra layer of security, because a '68 is super easy to get started without a key anyway. Personal preference only, but I would keep the wiring as clean as possible and either come off a switched lead or put in a solid state relay like has been suggested..

Steve

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Old 05/07/2018, 09:31 PM   #29
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You can accomplish the same thing just putting a jumper from the small stud on the solenoid (Brown wire) to the Coil + terminal. There's 12V there when the key is in the Run or Acc position.

Neil
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Old 05/08/2018, 04:59 AM   #30
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Quote:
Originally Posted by franklinair View Post
You can accomplish the same thing just putting a jumper from the small stud on the solenoid (Brown wire) to the Coil + terminal. There's 12V there when the key is in the Run or Acc position.

Neil
I'm pretty sure there is only 12V on the small stud on the starter cable side when the key is in the "Start" position.

Steve

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