Coil Voltage!!! Wtf!

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dusterbd451

dusterbd451

"cruise, race, live!"
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Hello everyone!...i am new to the forum and this is my first post so hopefully there is some help out there for me and my ignition.
Here is the issue: My car originally had a worked small block with a stock ignition (w/ msd coil and wires) and all was fine. I since have rebuilt my duster and converted to a 451 stroker with all Pertronix flame thrower coil / distributor, and Second strike box. No here is the issue.....when checking voltage accross the coil, it only reads 3.*** volts on my fluke meter...not enough for spark. with the wires off the coil, there is 12.*** volts at the (+) wire, and when metered accross the (+ / - ) coil wires by themselves, there is 12.*** volts, but when hooked up to the coil, there is only 3.*** volts.
My wiring, as refered to me by the tech support @ pertronix has my factory coil wires, the (+/-) off the distributor, and the switched power for my control box all running off the coil. Has anyone had this issue or is there any help for me!!! ....I want to get my ole' girl on the road before it snows up here! Thanks
 
I agree (WTF).. Electrical problems are never very fun and sometimes don't follow logic per se, but lets see if we can isolate the problem.

Known: wires from the stock harness read 3v when connected to the coil and 12v when not. correct?
Measure the voltage from coil (+) to engine (-) and chassis (-) and see what you come up with. Also you might want to power things independently of one another for testing
 
ORIGINAL MESSAGE:
I agree (WTF).. Electrical problems are never very fun and sometimes don't follow logic per se, but lets see if we can isolate the problem.

Known: wires from the stock harness read 3v when connected to the coil and 12v when not. correct?
Measure the voltage from coil (+) to engine (-) and chassis (-) and see what you come up with. Also you might want to power things independently of one another for testing

CORRECT:

-I hooked a jumper wire directly up to my battery (-) and tested, and it is still 3V. The only way i tested that got a 12V reading, was when i had everything hooked up as explained, and had a wire running directly from my battery (+) to the (+) on the coil....but i do not want to run a direct switched power from my battery...that is what the ignition is supposed to do.

Any more thoughts?:read2:
 
The second strike box is a capacitive discharge box that sits on top of the standard inductive ignition. You should be able to just disconnect the box from the coil and the engine will run on the ecu that is inside the Pertronix distributor. I believe the pertronix coil does not require a ballast resistor so you should have replaced the ballast with a jumper.

As far as reading voltage across the coil; if the engine is not running and the key is on you should read zero volts across the coil primary because there is no current flowing. If you are reading 3 volts then there is another path to ground which could very likely be in the second strike box. Or, there could be a problem with the control box in the Pertronix distributor. Measuring the + to ground you are reading the expected 12 volts.

I would disconnect the second strike box and see if you can get the engine running without it. Since the Pertronix distributor does not have a dedicated ground wire make sure you have a good ground connection between the distributor housing and the block.
 
If you have 12+ volts on your factory harness coil wire, then your problem is NOT in the wiring. (Unless the harness has been spliced, patched, or otherwise degraded....using a #18 wire in place of a #14, etc).

If you attach the factory harness coil wires to ANYTHING and the voltage drops as you said.......one of two things come to mind:

1. Whatever is attached to the POSITIVE coil wire is pulling too many Amps (this would drop Volts). If I understand your explanation of the problem, I would suspect your new Pertronix coil may be defective. You can try it on another vehicle.

2. The NEGATIVE coil wire is not making good contact. (have you ever noticed a vehicle with a dim headlight or tail lights that go out when hitting the brakes? (Bad ground preventing full current flow)

What is the second strike box? Can you bypass it and re-check the voltage at the coil? Something in that ignition system is draining your voltage. Should be a process of elimination. I hope this helps. Keep us informed. David
 
THANKS for the info....I willtry these tonight and let you know the results tommorow. As for myself, i thought i might have a defective coil, so i am going to buy another one and try it out to eliminate that possibility.

I have tried this also with the 2 wires from the second strike box dis-connected, and i had the same readings. So i will disconnect it and use the new coil and see what happens.

As for the ballast resistor (by this I am guessing the ceramic looking block on the firewall.??)) it is still plugged in with the factory harnesses that plug into it. Should it be omitted and have a wire jumped? If so..which wires?

I noticed that it was getting rather hot when we hooked on the battery and began testing....so we swapped it with the one from my bro's duster and had the same issue.

Should it be omitted??
 
I believe if you read the installation instructions for the pertronix coil it will say you do not need the ballast resistor.

I would just take a piece of 18 guage wire an put male spade connetors on the ends and plug one end of wire into the connectors that were plugged onto the ballast resistor.

Also, you need to find out why you were measuring voltage across the coil. As I stated before you shouldn't read anything if the engine is not running and the key is on. The 6-8 volts you here people talk about is from the coil + to ground not across the coil.
 
i will look over the instructions again for the coil to find out..., and if so i will by-pass the ballast

As for the voltage, you should read voltage accross the coill wires when the ignition is on because the power goes through your coil and flows through to your ignition box and in turn into your dist. Also, your vehicle runs with the ignition in the on position...so there would have to voltage there.. Tell me if I am off my rocker here, but that is my logic.

Also, the coil (-) wire goes to ground anyways. it flows to the ignition box and is grounded to chassis through the mounting.
 
Alright, I placed jumper wires in place of the ballast and the voltage has now jumped to 9.XX Volts....better, but still not there. I ran a ground wire from the mount bolt on the ignition box direct to a chassis ground just to make sure it was grounded,and ran a ground wire direct from the (-) terminal on the coil to chassis, and the reading stayed around the same value. I also tried running a direct 12v line from my battery post just to see what it would do....still around 9v. (?)

me and my brother were thinking about this for hours lat night, i an had an idea i thought i would run by you guys and tell me if this idea holds water. If I switched to a pertronix dist., coil, sec.strike box...do I still need to run the facory electronic ignition box??. Because i was tracing wires back, and the only wires that go to the box are 2 wires from the ballast (which are both 12V now because I jumped them together), one wire is the coil ground *(which I can easily re-route to a chassis ground), and the other 2 are the factory distributor wires that are not being used in this setup.....does this make sense...I am not entirely clear on what the ignition box does.

Thanks!

SG
 
Mistake; If you run a wire from the - of the coil to ground there will never be any switching on an off of the power to the coil and it will never run.

The Pertronix distributor is a self contained standalone igntion. It does not need the factory control box (and the factory control box can't be used with it) or the second strike box to run the engine. The Second Strike is kind of a an odd ball device, no one else makes anything like it. It takes a standard inductive ignition points or electronic then puts a capacitive dishcahrge voltage across the coil a few degrees after the points open or control box switches off and fires the first spark. Where the leads from MSD, Accel, Mallory and Crane boxes are the only things connected to the coil + and - terminals.

Why not go back to square one.

1. Take all the wires you have connected to the coil + and - terminals off.

2. Connect the blue wire that orignally came from the ballast resistor (now jumpered) to the + side of the coil.

3. Connect the red wire from the Pertronix distributor to the + side of the coil.

4. Connect the black wire from the Prtronix distributor to the - side of the coil.

If the distributor is installed correctly and its not bad and the coil is not bad and there is voltage at the + side of the coil with the key on AND when cranking the engine will run. The second strike box is not needed and the factory control model can not be used.
 
thats what i was figuring last night...because these units can be used in custom / street rod instances where the control box would not be needed. Well that is my night tonight. Thanks for all the info and I will let you know how / when that works....there are not many ideas left in my head!! thanks again.

Steve
 
I did all of that , and there was 11.XXXv at the coil, and 9.*** while cranking, but still no spark. I talked to some local guys that have used these and have said that they have had these issues and most resolve when a direct 12v from the battery was hooked up to the distributor. I am going to try that tonight, and i also have a stock distributor in my hands that is going in if it doesn't work......we'll see how that goes...
 
it was found out that the ignior in my distributor was faulty.....so i put all new stock ignition in and she fired to life right away...and let me tell you, for being my first BB...she sounds gooooooddd...thanks for the help!

SG
 
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