Electrical help needed

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35steveq

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Hello, I have studied TONS of threads on the topic, but none have the exact issue im having. Hopefully the experts can chime in...
64 Barracuda, purchased as a shell. Installed new motor, electronic MP kit, later model voltage regualtor and2 field alternator.
My problem is, only 5V to posative side of coil. I ran a jumper to straight 12v and it starts right up. If I pull jumper off, immediately dies. I have double checked ballast wiring, ECU wiring, all seems to be per diagram instructions.
I must be overlooking something simple, but short of spending another 300 on a standalone MSD box. I should be able to make this work.
Any leads on where to start??
Appreciate any help...
 
Ohm out the ballast resistor and also see if you get 12V to one side with the key on to start
 
OK whats the voltage on the output side of it? The 1.5 one it is a bit high but not that much.
 
Follow above, but you may want to do a resistance check thru ignition switch. It may be able to carry voltage but not current.
 
5v on other side of ballast with key on in run position. The same as + side of coil.
OK pull the wire off the out side on the ballast to the coil and see what it is. If it is 5V bad ballast. Next step is take the wire off the coil and see what the voltage is. You have the MSD hooked up like this?
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Follow above, but you may want to do a resistance check thru ignition switch. It may be able to carry voltage but not current.
was just going there next!:rofl: This is when you want a load light!
 
was just going there next!:rofl:
Well Dam!!! After pulling my hair out last night till 3am, I came out this morning to start trouble shooting per your help, it fired right up with no jumper wire!! I might be good. Hahahaha

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You could have moved a wire and it is making a good contact. Glad it is working but wiggle the wires when it is running to be safe.
 
No sweat also some of those orange boxes are fakes look at the transistor if it has printing on it or is tall prob a fake. How do you have the MSD running a box?
 
No sweat also some of those orange boxes are fakes look at the transistor if it has printing on it or is tall prob a fake. How do you have the MSD running a box?
I have one on the shelf, was trying not to use it on this car.. thats why I wanted to try factory components. I didnt install the MSD
 
I have one on the shelf, was trying not to use it on this car.. thats why I wanted to try factory components. I didnt install the MSD
And yep, willing to bet orange box in Chinese.. bought as a kit from JEGS, at least it has Mopar stickers.. lol
 
Those kits are notorious for it. still see if you can make it cut out again to see if it is something else stupid.
 
64 Barracuda, electronic MP kit, later model voltage regualtor and2 field alternator.
, only 5V to posative side of coil. ...

I would highly recommend you check/ go through the entire path from battery--bulkhead connector--ignition switch--to ballast etc

HERE IS the thing. Assuming everything is as it should be there are TWO sources of power to the coil.....

1....In "run" the key feeds power to the ballast which goes to the coil.
2....But in "start" the "RUN" circuit goes DEAD. The only power to the coil is the brown bypass "IGN2" wire. This is hot "in start" but is not the same as the "start wire" The start and the IGN2 are separate switch sections in the switch.

What this means is that if EITHER of these circuits has a problem here's what will happen

1...If the "run" circuit goes dead/ poor/ low/ bad / etc, the car will likely not get enough power to the coi to run, and will not start if you try by jumpering the start relay

2...If the IGN2 "bypass" circuit goes bad, the engine will not fire in "start" but might/ probably start if you jumper the start relay, key in "run."

============================

Also if some bad connection or defective ignition switch is not providing full power, and you "do" accidently get the car to run, it is likely the thing will OVERCHARGE the battery as the VR will be getting LOW voltage and will attempt to "ramp up" charging voltage to compensate.

You have a shop manual/ wiring diagram? First thing "if not" is to wander over to MyMopar. Download them free
 
A most important fact has not been mentioned, unless I missed it.
The coil current grounds through the ECU box. So make sure the mounting bolts/screws make good [ clean ] contact with the box AND the car body.
 
A most important fact has not been mentioned, unless I missed it.
The coil current grounds through the ECU box. So make sure the mounting bolts/screws make good [ clean ] contact with the box AND the car body.
That is true but at this point whether the box is grounded is not the issue

If the ballast was getting 'full' 12v from the key, both sides of the coil would show 12v as it would not be drawing current, if the box was ungrounded

At this point I don't think anyone is sure he getting much out of the bulkhead connector
 
A good reason not to use those early Chrysler ignition systems. Anything that uses a ballast resistor is old tech and adds those issues. That includes older after-market ignitions like Pertronix Ignitor (original, not II, III), Crane Cams XR700, and such. The GM 8-pin HEI module + coil is a better choice to upgrade from a points system. It will trigger from a Mopar e-distributor. The ballast resistors are too low to measure resistance accurately, so better to measure voltages as you did. When steady running, with a ballast, you should see ~8 VDC at coil+ (rel to distributor case). When cranking, it should be the full 12.6 VDC battery voltage (key switch bypasses ballast). Of course with a modern ignition (no ballast), you should see close to alternator output (~14 VDC) at coil+ when running. My old Mopars have a relay providing IGN power, so no worries with drops across the key switch. I installed a relay/fuse box from a ~1999 Jeep (black box in Avatar).
 
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