What causes this?

[Firetodd]

So I have had some problems with not being able to start my car. I have no spark from the plug wires. Previously, I had found a bad 12v feed to the coil that seemed to fix the problem, but it again has no spark.

Here is my car: 67 Charger with a 383hp, mostly stock. It had a Mopar Orange box with corresponding distributor. I worked with Ron to put a Firecore ready to run unit in and it ran very well for a couple months. Then I started have issues. I pulled the Firecore unit and put the old Mopar set up on and it fired right up. So I thought maybe I either had a bad Firecore unit or installed it wrong (a likely possibility).

I then pulled the Mopar unit and re-installed the Firecore unit. I walked to the ignition switch and it fired up immediately! It ran great! I took it for a 10 mile drive and everything was great. I checked the voltage at the coil and it showed a wildly fluctuating voltage. I took a video: http://youtu.be/gTAx8APJ_6w

So I know that the Firecore unit works fine, but I have a gremlin. That brings me to this morning. I talked with Ron and he suggested a few things to check. I went out and it again won't start. No spark after it ran great yesterday. I tried grounding the voltage regulator to the block, no spark. I tried running a hot wire from the battery to the coil, no spark. I tried swapping the coil discharge wire to the distributor with a spare I have, no spark.

With the car not running, and the key in the run position, I have 12 volts at the coil. Attempting to start, with the key in the start position, I have 9.5 volts at the coil. I have no spark. I have also swapped coils to known working units. Today, I ordered a new electronic voltage regulator from Year One. What am I missing?

[Ghoste]

Shouldn't that be the other way around, 9.5 in run and 12 at start?

[Firetodd]

Not sure Ghost, but I was thinking that the voltage was dropping while running the starter.

[john108]

Thinking about the voltage:  There are 2 wires coming from the ignition switch (IGN1 and IGN2).  They go to opposite sides of the Ballast resistor.  If they are reversed, I think that would affect the voltage readings.

[Dino]

I had similar issues which turned out to be a bad Firecore distributor.  I chased that gremlin for a while but Ron came through and solved it.   
9.5V cranking sounds about right.  That's around what I get as well at the coil.  The two ignition wires that run to the ballast are hooked together for the rtr unit. 

[fy469rtse]

There's one common thing interrupting path of wiring ,
I would pull plugs at bulk head and check connections there , bad contact , high resistance
Have a good look at all connections there , some thing bad  loose connection  ?
Bad ballast resistor,
There's a break or bad connection there some where,  sorry it's going to take test your patience to find it

[Firetodd]

I will check the bulkhead connections and clean each wire and put some dialectic grease on them one by one. I can't wait for the new voltage regulator to get here, as I will be upgrading to an electronic VR (maybe that will help).

I am wondering if I don't have two problems. Maybe the Firecore unit has an intermittent issue AND I have a bad VR. It still escapes me how if I have power to the coil and the distributor, a known working coil, and good plug wires that I should have at least a spark.

[moparnation74]

You have the RTR firecore unit correct?  Is it properly grounded?

VR is an easy replacement before moving forward, I agree.

Maybe the ecu unit in the distributor is faulty.  Did you test the spark plugs for fire?
I am sure the rotor is turning when you spin the motor, correct?
It is rare for a coil to go bad but can happen.

[Firetodd]

I replaced the voltage regulator today, but as suspected, still no spark. So I pulled the Firecore distributor and put the Mopar Orange ecu and distributor back in. It fired right up! The voltage at the coil stays steady at 6.5 volts as I am now using the ballast resistor. So I think I did have an issue with the voltage regulator.

Now I just need to figure out the issue with the Firecore unit. Crazy thing is it worked for several months. Perhaps the bad voltage regulator damaged the Firecore unit or the Firecore unit damaged the VR?