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Are you ready for a real weird one? Random NO spark from a MP electronic ignition system despite numerous parts swapped around...

I am going back to the beginning Greg. I don't have the time to read through 21 pages of comments to see if this has been mentioned or not. My new to me 64 Polara has Mopar electronic ignition on it and I am experiencing a similar no start condition like you. You can jumper the coil + terminal from the battery + and it will start. The voltage drop while cranking goes down to 10.9 and 10.8 at the ECU. I am wondering what the minimum voltage is for the ECU's. I need to do a little testing. Does it have spark after a battery charge when the surface voltage is around 13v. or so? Could I provide an external 12 v power source for the ECU and the car would start? This theory is all about the starter draw pulling the battery down below the minimum operating voltage of the ECU. @Dave6T4 mentioned that he replaced his old starter with a new style Nippon Denso and not only did it spin over faster, the car started easier. Like he said
"I think the old starter was pulling so much power, there was not much left for ignition system." I think he might be onto something. I might try the battery charge test first just to see what happens. If low voltage is the issue, a stronger battery sure could help. So could a news starter. Even a different ECU that isn't as picky about minimum voltage may fix the issue. I may end up going back to a plain old single point distributor with a Pertronix in it.
I've also had a mini-starter go bad after a few years and it would drain the battery and cause starting issues. I finally took it to my ace mechanic who is excellent at tracing electrical issues and he traced it to a short in the starter. Replaced that starter with another mini starter and its been fine ever since.
 
I rarely get simple problems to post about. I get the weird ones that test my skills and patience.
This car:

View attachment 1633388

Has a 440 based 493 with mostly aftermarket stuff on it. It was a 318 model so when I did my first 440 swap to it in 2001, I converted it to the then popular Mopar Performance electronic conversion kit. The distributors they used for this were physically similar to the stock electronic distributors from the outside but had Mallory internals scaled down to fit a Chrysler housing. Smaller advance weights, lighter springs and generally not that great. They get spark scatter, unstable timing and can cause erratic idle issues. I worked though most of that so this one performs okay.
Here is the ongoing issue that I've encountered several times since around 2012, giver or take:
It could be a cold start or a warm restart....I get no spark. None. I touched nothing, I moved nothing, it just started and ran normally moments or days earlier and now it spins and won't fire. Sometimes I've changed the ECM and it starts fine immediately afterwards so I blamed the ECM since we all know the spotty reliability of the Orange box...

View attachment 1633389

Once I was at the Sacramento Autorama on display and it was the day to take our cars and leave. No spark, no tools, no spare parts. I twisted connections, wiggled wires and cussed a lot. Nothing helped. About an hour of screwing around, then I sat inside and tried again and BOOM, it fired up like normal.

Weeks afterward, a car club member offered to help me rewire the engine side to avoid future NO start issues. It started fine before he worked his magic. Afterwards I had the NO spark again along with some funky headlight door reactions. (That I figured out some 10 years later when I installed the CrackedBack headlight relays!) I gave up and ordered a new harness from Evans.

Randomly over the years, it has happened, almost every time here at home, thank the Lord for that at least. I've tried bypassing the ignition switch with a spare one attached from under the dash. No change, still NO spark.
I've tried Ether/Starting fluid with mixed results. Sometimes it fires up immediately but I wonder if that was just how the damned thing is....maybe the ether spray made no difference and it was going to start when it was ready no matter what.

In 2017 I wanted to weigh the car and I had to get home (In my work truck) in time to get the Charger to the scales. One time it stalled without reason at an intersection and after trying a new coil then ECM, it fired up. The next day, It stalled in my driveway and putting the previous coil back in allowed it to start.
Yeah...It has been musical chairs with parts.
A couple of weeks ago I was tinkering with the A/C and pulled the low pressure switch. The car stalled and shut off. NO spark again. Why? What the heck does the low pressure switch have to do with the ignition wiring? I swapped in another ECM and it started up.

It feels as if I'm on the receiving end of some voodoo curse, like some "force" is watching me and selecting specific parts to conk out and stall the car, then just allowing it to start up again. Yeah, I know that is impossible, it just seems really strange.

I've adjusted the distributor air gap as per the FSM and other publications. .008 set with a brass feeler gage.
************************************************************************************************************************
EDIT:
Sometimes it will feel like it wants to start as I turn the key back to LOCK.
Thanks--sounds a lot like the issue that just started for me. Your headlight door comment also caught my attention--last week for no apparent reason the doors stopped working. I rarely drive at night so I was not too concerned. I just lowered them manually and figured I'd get to it when I get to it. I didn't think it was anything other than a coincidence when this issue started a day or two later!
 
@Kern Dog - since your install of the new battery, would you call your electrical no spark issue at the ECU now solved or is the electrical system still showing signs of non-ideal behaviour?
 
Since I changed the battery, I have been swamped with other things here to do.
Rich and I have been working on rebuilding the engines in these cars...

IMG_9295.JPG


Dart blue 1.jpg


360 A24.jpeg


360 A25 A.jpeg


I've been working with my nephew building a Go Cart...

3 2 25B.JPG


3 2 25C.JPG


Of course this place needs maintenance too....

5 24 2.JPG


5 24 3.JPG


The car has started consistently though since I moved the battery back up front and switched to this Lithium one.
 
Sorry, Mike. I missed this one from you.

I am going back to the beginning Greg. I don't have the time to read through 21 pages of comments to see if this has been mentioned or not. My new to me 64 Polara has Mopar electronic ignition on it and I am experiencing a similar no start condition like you. You can jumper the coil + terminal from the battery + and it will start. The voltage drop while cranking goes down to 10.9 and 10.8 at the ECU. I am wondering what the minimum voltage is for the ECU's. I need to do a little testing. Does it have spark after a battery charge when the surface voltage is around 13v. or so? Could I provide an external 12 v power source for the ECU and the car would start? This theory is all about the starter draw pulling the battery down below the minimum operating voltage of the ECU. @Dave6T4 mentioned that he replaced his old starter with a new style Nippon Denso and not only did it spin over faster, the car started easier. Like he said
"I think the old starter was pulling so much power, there was not much left for ignition system." I think he might be onto something. I might try the battery charge test first just to see what happens. If low voltage is the issue, a stronger battery sure could help. So could a news starter. Even a different ECU that isn't as picky about minimum voltage may fix the issue. I may end up going back to a plain old single point distributor with a Pertronix in it.

That condition of where the low battery voltage possibly leading to ECU/Spark issues may be a real thing. The battery could be just charged enough to start the car but not have enough reserve if the carburetor were dry. If it started within 15 seconds, the battery would still be pulling a lot of juice to be recharged and I wonder if that somehow exposed a weak link in the ignition system.
I am just operating on theory though. I'd need someone more skilled with ignition systems than ME to feel more confident about it.
 
@Kern Dog - since your install of the new battery, would you call your electrical no spark issue at the ECU now solved or is the electrical system still showing signs of non-ideal behaviour?
A few days ago, I checked voltage of the battery. It was 13.06.
The car has consistently started and ran normally ever since I replaced the 5 port plug at the ECM. The battery holds a charge and does not seem to drop off like the NAPA battery did. It drops off just sitting on the shelf here.
It is nice to have this problem behind me.
What did I learn by this?
Well, I've heard for years that a majority of electrical problems are due to poor grounds.
In this case, it seems like the ECM plug has had an inadequate connection to the ECMs themselves which may or may not have led to failures of the ballast resistor or the ECMs themselves.

Old plug:

11 24 12.JPG


New plug:

11 24 10.JPG


Notice how the terminals look wobbled out on the old plug. The rubber boot fit snug around the plastic on the ECM but the brass terminals may not have had adequate contact.

1753344931614.jpeg


Looking at the schematic below....

1753344993413.jpeg


#1 terminal goes to the ballast resistor.
#2 goes to coil negative.
#3 is unused.
#4 and 5 go to the distributor.

Look again. Number 1 to the ballast resistor is deformed. # 4 to the distributor is too.

1753344931614.jpeg


It is reliable now though!
 
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A few days ago, I checked voltage of the battery. It was 13.06.
The car has consistently started and ran normally ever since I replaced the 5 port plug at the ECM. The battery holds a charge and does not seem to drop off like the NAPA battery did. It drops off just sitting on the shelf here.
It is nice to have this problem behind me.
What did I learn by this?
Well, I've heard for years that a majority of electrical problems are due to poor grounds.
In this case, it seems like the ECM plug has had an inadequate connection to the ECMs themselves which may or may not have led to failures of the ballast resistor or the ECMs themselves.

Old plug:

View attachment 1889746

New plug:

View attachment 1889744

Notice how the terminals look wobbled out on the old plug. The rubber boot fit snug around the plastic on the ECM but the brass terminals may not have had adequate contact.

View attachment 1889747

Looking at the schematic below....

View attachment 1889748

#1 terminal goes to the ballast resistor.
#2 goes to coil negative.
#3 is unused.
#4 and 5 go to the distributor.

Look again. Number 1 to the ballast resistor is deformed. # 4 to the distributor is too.

View attachment 1889747

It is reliable now though!
Follow-ups to problems (especially weird ones) are always cool, thanks Greg!
Those terminals do look a little worn in your pic. Sometimes the connection between the wire and terminal goes bad too, which you can't see because it's inside the rubber. It may show continuity on the ohh-meter but not be having good enough coitus to to carry power through the connection reliably. And shame on me but I didn't read back through all the posts, and I apologize if this is a stupid question but do you screw the boot on as well? That keeps things from moving.
 
after reading this tome, and after all the trials and errors you went through KD, one other suggestion if i may.
please get rid of those "bolt on" temporary battery cable terminal ends.
after almost 60+ years of screwing around with vehicles, those things have caused more problems than they are worth ! i would hate to see you needing to chase more bugaboos.............
not trying to be an ***.
just my lifetime real world experience with those damned things.
your mileage will vary.
:drinks:
 
I agree to a point but it isn't humid here. The terminals stay dry for the most part.
 
That was more than corrosion. I think that was from attaching and removing it so many times over the years. The terminals in the plug were wobbled out.
I repainted the engine bay twice, relocated the ECM a couple of times and tried a few different ECMs over the years.
This is just a guess but I think all the on and off, the twisting and pulling may have simply loosened the terminals enough to not make proper contact.
Who knows for certain. I do know that the new plug fits nicely and that the No-Spark issues seem to be gone.
Thanks for chiming in.
 
Post #20 and Post #30 way way back in the beginning

Both mention that ECU Plug and female connectors

Also a dab of Dielectric Grease on each pin would have gone a long long way


Peace , fingers crossed
 
Post #20 and Post #30 way way back in the beginning

Both mention that ECU Plug and female connectors

Also a dab of Dielectric Grease on each pin would have gone a long long way


Peace , fingers crossed
Yes, I did look at the old plug and by itself, it looked fine. When compared to one that had never been used, it was apparent that the female terminals were not as tight.
 
I've had new cables cause a problem, bad connection as made at the terminal to the wire.
 
If the ECU connector was expanded female terminals, this will likely result in a poor, high-resistance connection.
And this can result in building up an oxidation level due to the higher heat. As the layer of oxidation builds
eventually there will be no connection for electricity to flow through...

Just my $0.02... :thumbsup:
 
That makes sense to me.
Given my rudimentary understanding of electrical things, that is what I figured as well.
 
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