Carcinogen
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I had electrical issue that was intermittent. Found wire corrosion on the inside, outer insulator looked good but inside was brown with spots of green corrosion.
Are you ready for a real weird one? Random NO spark from a MP electronic ignition system despite numerous parts swapped around...
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Here is an interesting nugget of info:
This is the text included in the Rick Ehrenberg electronic distributor he sells on ebay. It comes with this ECM and ballast:
Now, Rick is a strong proponent for OEM type stuff based on the engineering but he does seem a bit fanatical about some things.
I don't know the Ohm ratings of any of the coils I've used.
Here is a thought....what IF he was right and I had a coil with resistance rated too low?? What if that caused temporary disruption of the ECM??
I have always used the ballast with everything except the FBO box but never paid attention to the coil resistance numbers.
Did I accelerate the risk of failure to the ECMs as a result of that?
This is the text included in the Rick Ehrenberg electronic distributor he sells on ebay. It comes with this ECM and ballast:
Now, Rick is a strong proponent for OEM type stuff based on the engineering but he does seem a bit fanatical about some things.
I don't know the Ohm ratings of any of the coils I've used.
Here is a thought....what IF he was right and I had a coil with resistance rated too low?? What if that caused temporary disruption of the ECM??
I have always used the ballast with everything except the FBO box but never paid attention to the coil resistance numbers.
Did I accelerate the risk of failure to the ECMs as a result of that?
definitely worth considering.
You just recently installed the Rick E distributor and blue ECM with matching ballast resistor, correct?
You just recently installed the Rick E distributor and blue ECM with matching ballast resistor, correct?
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Not yet. I have it right here:
The car started running again with the same setup it had before the most recent No spark event. My thought is that the existing Mopar Performance distributor may or may not be to blame or a contributing factor in this. To use this new distributor, I'd need to limit the total advance it allows to somewhere around 14-16 degrees to maintain my current tune. FBO does sell these plates:
If I were to start over, there are plenty of choices I could pursue. Since I already have this, I might go ahead and use it.
Ok I didn’t read with a detail on every reply, just a quick pass over the thread… just two things to say from my point of view… first:
The yellow wire on that diagram is not correct for pre 75 or 76 cars. On earlier cars the wire arriving there is brown coming from ign switch as IGN2 signal being the ballast bypass. On 75 or 76 (can’t recall) the ballast bypass comes from starter relay, saving one wire coming out from cab. The starter relay on these are diff with an extra prong to feed the ballast while cranking, labeled BAL:
SECOND. It seems nobody has suggested to measure or check the dist pickup coil conditions. It must read anything between 150-900 ohms (althought tipically 250-300 on all those I have checked). This same reading must be read on dist plug AND the ECU plug. Why I say this?, because you can get the correct reading at dist plug but a bad contact on the engine harness side of same plug, so thesignak not reaching to the ECU.
Once I had a similar experience, until found in my desesperation that shacking/moving the dist plug got to start the engine again… what I did in place? (I was on a parking mall at night)
-Clean contacts on both ends.
-Expanded/contracted (depending if male or female) the terminals at plugs to get back some pressure on contacts.
Maybe a month later decided also to replace the pickup coil, not because the coil was really damaged, but just because the wires running to plug could be maybe broken at the plug end? They are WAY thinner than the engine harness side, easy to get break, specially with heat engine, thin wire cover and the weakness between wires a the rubber plug transition.
The pickup coil is cheap and I didn’t want to splice a new plug on pigtail to get an ugly splice there so went for a new unit.
Not saying is that what is happening on this case, but sharing my experience on a similar issue.
Later on, also began to get Chrome MP ECU failures… twice in 3 years until went for the A688 FBO box (fail again in just 4 months), and finished with the Rev-N-Nator with a couple of weeks experience with the HiRev7500 box and couple more with an orange MP box meanwhile the Rev-N-Nator was being released and shipped to me. But that’s maybe a diff story.
The HiRev7500 is planned to be my spare at trunk. But a friend on mine also got it and failed in a year or so.
The yellow wire on that diagram is not correct for pre 75 or 76 cars. On earlier cars the wire arriving there is brown coming from ign switch as IGN2 signal being the ballast bypass. On 75 or 76 (can’t recall) the ballast bypass comes from starter relay, saving one wire coming out from cab. The starter relay on these are diff with an extra prong to feed the ballast while cranking, labeled BAL:
SECOND. It seems nobody has suggested to measure or check the dist pickup coil conditions. It must read anything between 150-900 ohms (althought tipically 250-300 on all those I have checked). This same reading must be read on dist plug AND the ECU plug. Why I say this?, because you can get the correct reading at dist plug but a bad contact on the engine harness side of same plug, so thesignak not reaching to the ECU.
Once I had a similar experience, until found in my desesperation that shacking/moving the dist plug got to start the engine again… what I did in place? (I was on a parking mall at night)
-Clean contacts on both ends.
-Expanded/contracted (depending if male or female) the terminals at plugs to get back some pressure on contacts.
Maybe a month later decided also to replace the pickup coil, not because the coil was really damaged, but just because the wires running to plug could be maybe broken at the plug end? They are WAY thinner than the engine harness side, easy to get break, specially with heat engine, thin wire cover and the weakness between wires a the rubber plug transition.
The pickup coil is cheap and I didn’t want to splice a new plug on pigtail to get an ugly splice there so went for a new unit.
Not saying is that what is happening on this case, but sharing my experience on a similar issue.
Later on, also began to get Chrome MP ECU failures… twice in 3 years until went for the A688 FBO box (fail again in just 4 months), and finished with the Rev-N-Nator with a couple of weeks experience with the HiRev7500 box and couple more with an orange MP box meanwhile the Rev-N-Nator was being released and shipped to me. But that’s maybe a diff story.
The HiRev7500 is planned to be my spare at trunk. But a friend on mine also got it and failed in a year or so.
Last edited:
Geoff 2
Well-Known Member
Semiconductors in the ECU can suffer from something called thermal runaway; basically, they overheat & their electrical characteristics change. They can return to 'normal' when they cool down.
If an ign coil is used with a low pri resistance, say 0.5ohms, then the power transistor in the ECU could overheat from the higher current it is passing.
Could this be the problem? Possibly. This is why it is soooooooooo important that the ign coil primary resistance is matched to the ECU or module being used.
If an ign coil is used with a low pri resistance, say 0.5ohms, then the power transistor in the ECU could overheat from the higher current it is passing.
Could this be the problem? Possibly. This is why it is soooooooooo important that the ign coil primary resistance is matched to the ECU or module being used.
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Most of my life I have probably stumbled my way through, somehow averting disaster and mayhem due to some guardian force.....
The phrase "Did I get lucky?" is one of my favorites. The answer may very well be YES in many situations.
The phrase "Did I get lucky?" is one of my favorites. The answer may very well be YES in many situations.
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Impossible.
if you have doubts about coil resistances measurement.
And a reference chart I found around… pretty sure more available searching
And a reference chart I found around… pretty sure more available searching
Mopar Miki
Active Member
meter leads when crossed should zero out no matter what the setting is, ie ohms or volts. This is sop when using a meter. If the display does not zero the the meter is cheap and should not be trusted or you have a good meter with bad leads.
I do not see where the pickup was checked with an ohm meter after a no sparks situation. Voltage checks? As the distributor turns it makes and brakes the continuity which can be readily seen by the ohm meter.
That ignition box from that guy yu all love is a cheap china knockoff, real boxes have a real transistor which requires an transistor insulator plate which is missing in the picture. Real switching transistors have a base, emitter and collector....look it up
I do not see where the pickup was checked with an ohm meter after a no sparks situation. Voltage checks? As the distributor turns it makes and brakes the continuity which can be readily seen by the ohm meter.
That ignition box from that guy yu all love is a cheap china knockoff, real boxes have a real transistor which requires an transistor insulator plate which is missing in the picture. Real switching transistors have a base, emitter and collector....look it up
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Thanks, Nacho!
Couple more thoughts.. the chrome accel coils have been extremely durable, and flexible with BRs and ecus, in my testing.
You had mentioned tach .. disconnect it, it can ground out the - signal.
We discussed pu coil resistance in the 6pk thread.
Kiwi nailed the usual suspect problem, connections. I would go in and squish them together. The under column ign, bulkhead, ecu connector. With as many times the ecu has been replaced.. those wimpy bullet / pin pin connectors spread out.
And one more I wasn't going to mention, you said soldered connections.. they can grow resistance within.. there are no soldered connections from factory for that reason.. solder joints are used in low amperage electronics. And even those fail.
Did you get a 9v yet
You had mentioned tach .. disconnect it, it can ground out the - signal.
We discussed pu coil resistance in the 6pk thread.
Kiwi nailed the usual suspect problem, connections. I would go in and squish them together. The under column ign, bulkhead, ecu connector. With as many times the ecu has been replaced.. those wimpy bullet / pin pin connectors spread out.
And one more I wasn't going to mention, you said soldered connections.. they can grow resistance within.. there are no soldered connections from factory for that reason.. solder joints are used in low amperage electronics. And even those fail.
Did you get a 9v yet
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Looking at the wiring diagram here on page 4 the ECU power is coming from the hot side of the coil? This will give an erratic signal. I think you should try a clean power source.
I had a similar problem with a Holly sniper, I ran power directly from the battery to the ECU with a shielded wire and the problem dissapeared.
I had a similar problem with a Holly sniper, I ran power directly from the battery to the ECU with a shielded wire and the problem dissapeared.
even if it's not the issue, I like this. Why don't more of us connect the ECU like this?
do you have a link for the Mancini ECU? It's rev limiting? What ballast resistor ohm rating do you use with that setup?
Bee1971
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The ECU Blue/Yellow gets its power off the Ignition 1 Run Side of the Ballast Resistor - Full 12V - 14V
After 138 posts I'm still with kiwi post #2 you most likely have a bad wire/connection. If you haven't changed distributors maybe the pickup. My Satellite has had MP electronic ignition since mid 80's an 20k miles never reset the gap on pickup. Same oem ballast and coil except a 2 years with a Accel super coil. One thing is the starter relay for manual trans tab to housing ground a good, a little solder maybe to be sure. Didn't to make this so long.
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Since this issue was a random one, it may take awhile to know if cleaning the terminals had any effect. I'd sometimes go months between episodes of this. That is one of the reasons why it has been hard for me to fix....I'd swap a coil or ECU and it would start, then be fine for awhile.
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