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Ignition (electrical) help please!!!

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Old 06-12-2015, 01:23 AM   #1
mdt424
 
Join Date: May 2015
Vehicle: 1968 Ford Mustang
Location: michigan
Posts: 9
Default Ignition (electrical) help please!!!

Here's the problem, the wiring on my sons 68 Mustang has been butchered by people who had no idea what they were doing! The ignition switch was cutting out so we went to replace it & found an electrical nightmare, we sorted it out & have it wired to the way schematics show it & pictures I've found. Now it won't start at all.
Here's what I have:

* First the car turns over but there's no spark.

coil

* 0 volts at the coil + with the key off.
* 12.7 volts at the coil + with the key on.
* 10.7 volts at the coil + while turning over.

Solenoid

* 13.3 Volts at I (ignition) post on the solenoid when key switched on.
* 0 volts to the S (starter) side when key is on.
* 10.5 volts to the S (starter) side when turning over.

No spark at all, checked with a grounded plug & my timing light.

Jumped a lead from the battery + to the + on the coil & still no spark.

Any clues, suggestions or ideas?
We have the pink resistor wire but can't find what it's purpose is, can this be the issue? I haven't traced it to it's source yet.

Thanks!

Mark & Aaron
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Old 06-12-2015, 01:32 AM   #2
mdt424
 
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I also changed the coil to distributor wire & tried the old coil which was running the old engine.
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Old 06-12-2015, 10:58 AM   #3
Starfury
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First question: are you running points, or electronic ignition?

The pink resistor wire is supposed to run from the ignition switch to the firewall connection, and then a standard wire runs to the coil +. This should be the only source of power to the coil when the switch is in the "on" position. The resistor wire portion is supposed to drop voltage to the coil to keep from burning out points. If you're running electronic ignition, cut the resistor wire out.

If you're running points, the "I" terminal on the solenoid is supposed to feed back to the coil +. This terminal is only connected to B+ when the the ignition is in the "start" position (while the solenoid is activated). This gives full battery voltage to coil + while cranking, bypassing the resistor on the wire from the ignition switch, which aids in starting with a points system. If you're running electronic ignition and have disabled the resistor wire, this wire from the solenoid is redundant.

All that said, your wiring sounds right based on your voltage readings. You should be getting spark, assuming the distributor innards are working properly and the coil is functioning. Those are the places I'd start looking.
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Old 06-12-2015, 05:21 PM   #4
mdt424
 
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Thanks Tad. We are running a Pertronix Flame Thrower III. I will remove the resistor wire tomorrow. The distributor & coil are new & the car was running before the ignition problem. Thanks again!!
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Old 06-14-2015, 04:00 PM   #5
stefke
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Pop the distributor cap and crank it, see if it turns.
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Old 06-14-2015, 04:47 PM   #6
mdt424
 
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I've pulled the rotor cap & the rotor is spinning & can't be moved by hand.
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Old 06-14-2015, 05:39 PM   #7
ajzride
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As stated, ensure that you are getting the full voltage to the cool for a petronix unit. Also 10.3 volts seems low while cranking. Might want to throw a battery charger on it while cranking.
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Old 06-14-2015, 10:42 PM   #8
Starfury
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I thought that was a bit low as well, but I don't think it'd cause a complete no-fire situation. I still suspect the coil, module, or pickup as the culprit.

Do you have an old distributor to throw in? Spare coil?
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Old 06-15-2015, 06:11 AM   #9
mdt424
 
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Quote:
Originally Posted by Starfury View Post
I thought that was a bit low as well, but I don't think it'd cause a complete no-fire situation. I still suspect the coil, module, or pickup as the culprit.

Do you have an old distributor to throw in? Spare coil?
I have the distributor & coil from the 289. Same firing order, same block, would that work?
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Old 06-15-2015, 07:58 AM   #10
ajzride
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Actually the Pertronix are bad about not firing on low voltage. I'm not saying it is the most likely problem, but it is the easiest to diagnose, so I would probably try fixing that first.
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Old 06-15-2015, 07:58 AM
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