Coil Voltage question

[LowBikeMike]

Yes, remove distributor cap, put test spark plug in end of coil wire while other end is still attached to coil, ground test plug. Key on, all primary ignition wiring hooked up. Hold soldering gun or electric engraving tool close to distributor pickup coil, pull trigger. Spark plug will fire rapidly if all is in order.

 

[LowBikeMike]

I'm very much aware of how the reluctor/pickup coil operates in conjunction with the ECU. The strength of the induced trigger pulse, if too great, will damage the ECU's timing network that turns off the coil's current....you've been lucky thus far by not ruining the ECU with this method.....just thought you might like to know....
BOB RENTON

I'll politely disagree.

 

[Geoff 2]

Are you saying the magnetic field of a soldering iron/engraving tool will induce a small voltage in the p/up coil? That is the only way I could that working.

 

[Kern Dog]

No, the coil will not burn up if you run 12V directly to it. It may shorten the life of it but if the thing dies within minutes, it was going to fail soon anyways.
Exaggerating about stuff like this serves no purpose.
I have this exact same issue as the OP.
The car never stalled out from this, it just would randomly have a crank-crank-crank and no spark condition.
I too have the Mopar Performance electronic ignition kit in my red '70 Charger.
Each time I start by changing the ECU. Most of the time, that results in success. Other times I had to replace the coil. I kept the parts I pulled off and tested on other cars later and they worked fine so I still don't know what was actually to blame.
I don't have this problem on Jigsaw. It has a modified stock electronic 400 distributor in the 383. I have suspected that the MP distributor is to blame so I bought a new setup from a member here that includes a factory style distributor. To hell with that crappy MP unit.

 

[HALIFAXHOPS]

Not exactly sure what the soldering iron is supposed to do. The reluctor and pick up coil assembly coil assembly generate a negative going pulse, refined by the electronic components in the ECU to turn OFF the coil's switching transistor in the coil primary creating the spark. Do you mean soldering gun?? A soldering gun is a one turn secondary winding to the soldering tip causing it to get hot by high current and 0.01 AC volts. If you were aware of how the ECU operates, you would understand......trigger pulses turn the switching transistor OFF, creating the spark and then turning the transistor ON to recharge the coil's primary winding for the next spark event.....it's really not a mystery.....the ballast resistor LIMITS the coil's primary winding current and voltage to prevent overheating and limits the current the ECU's switching must handle during the turn on time......
BOB RENTON

So is the ecu you running a Mopar performance kit one? Usually says "authorized" or "replaces" on them on a side sticker. They have a really high fail rate if so. Also, can be the pickup coil when it gets hot and opens. Bob nailed it how a ECU works.

 

[RJRENTON]

I'll politely disagree.

Do know of or have you actually measured the voltage at the soldering gun tip or know what is the maximum voltage generated by the reluctor/pick up coil is or what the maximum voltage trigger voltage the ECU can withstand without damage?? There are several diodes and small transistors in the ECU's reluctor pulse shaping/dwell timing network that could be damaged by too high (accidently) induced pulse voltage by the method posed.....just because you've been previously successful does not mean, without knowing what the applied voltage to the reluctor sensing network is, OR what that maximum voltage is, that you've not damaged the ECU, making it prone to a future failure? Would you install crankshaft or rod bearings without measuring the clearances compared to maximum allowable? I would assume not.....the same philosophy applies.....just addtional points to ponder.....
BOB RENTON

 

[Mbrew]

I've had a very frustrating intermittent starting issue with my 360 powered '78 Magnum ever since I bought it nearly 2 years ago. It will crank with not even a hiccup some times, then after several to as many as 5 or 6 attempts at cranking, decide to fire up. I went through a period last month where it was usually starting on the first turn of the key, and I thought maybe the problem was fixed. Then at a cruise when I went to leave, it wouldn't start and after a half hour of me and some people there at the cruise helping out, it finally decided to fire up. It gets fuel, it just seems like it isn't getting spark when in the cranking position of the ignition.
Otherwise runs perfectly, I just need it to start!
All the lean burn stuff was removed prior to my ownership and has a Mopar electronic ignition, orange ECU box etc.
It doesn't help I'm not very good with electrical issues, so I've been chasing this issue since last year, replacing the ECU, ballast resistor, cleaning up the ground on the ECU etc.
The other day my friend brought over his multimeter and did some checks. One thing that caught his attention was he was only reading 5.5 v going into the coil. I checked with another guy I know who is knowledgeable on electrical and he said it should be 12 v.
Is that correct, and if so, what would cause the voltage to be low? The guy who is good with electrical troubleshooting said a weak battery or bad voltage regulator can cause that problem. Does the voltage regulator even tie in with the voltage to the coil?

Sounds like the ignition box needs replacing .
Ive had that condition too , would start just as i released the key.