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

[Kern Dog]

I rarely get simple problems to post about. I get the weird ones that test my skills and patience.
This car:

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...

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.
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EDIT:
Sometimes it will feel like it wants to start as I turn the key back to LOCK.

 

[kiwigtx]

I think you might have some funky connections in the bulkhead connector.

These faults are all over the place and if you are swapping parts around and get random faults with different parts swapped....that leaves the one thing that is staic.....the wiring loom itself. You might want to try and disconnect the three bulkhead connectors and spray some contact cleaner at the terminals, and maybe wipe a smear of di-electric grease on each male spade.....see how that goes.

I realise that one connector is for the wipers only, but why not check everything.

Also, has anyone funked with the wiring loom between the bulkhead connector and the ignition switch connectors??? I mean crimping on line-taps for stereo power etc? They can be a source of unreliability.....just like those precious acorn nuts that American Electricians are so fond of.

 

[Kern Dog]

I'm fortunate to have a stash of spare parts to test but I want to know how to target the specific problem, not just throw parts at it.
Today during the NO spark, I had power to the positive side of the coil. At one point, both the positive and negative lit up the test light.
No power to the distributor plug.
I pulled the plug off the ECM. See the schematic below:

The wire that they label as "Unused" is green with a red tracer. I do have that and no, no power seems to go to it but....It traces back to terminal L on the middle bulkhead plug on the firewall, then inside to the horn relay. That wire is supposed to dead end but Evans wiring ran it from the ECM plug to the bulkhead connector. That seems wrong. The horn relay should go to the horns, right???

The reason I mention the green wire is because I wondered if somehow the horn relay was back feeding trace voltage to the ECM somehow. I reached under the dash and unplugged it, still NO spark.

Today, I was filling the A/C system with Freon/refrigerant and was almost done when the car stalled and would not start. Yes, again, NO spark. I did the usual test light and ECM swap with no changes. 90 minutes later I sprayed ether down the carb and BOOM, it started.

 

[Kern Dog]

I appreciate all input. I'm not as skilled with these things as some other aspects of these cars.

I think you might have some funky connections in the bulkhead connector.

I bypassed the ammeter in 2015 and added fusible links. The bulkhead connectors were cleaned then but could maybe use some more attention.

These faults are all over the place and if you are swapping parts around and get random faults with different parts swapped....that leaves the one thing that is static.....the wiring loom itself. You might want to try and disconnect the three bulkhead connectors and spray some contact cleaner at the terminals, and maybe wipe a smear of di-electric grease on each male spade.....see how that goes.

I realise that one connector is for the wipers only, but why not check everything.

The wiring on the inside was totally stock and unmodified when I got the car. It is in surprisingly good condition. I did melt a few wires in 2019 when I accidently connected a ground wire to the fuse panel. I've since repaired it and have had no trouble with the repairs. This NO start issue happened before that and since.

Also, has anyone funked with the wiring loom between the bulkhead connector and the ignition switch connectors??? I mean crimping on line-taps for stereo power etc? They can be a source of unreliability.....just like those precious acorn nuts that American Electricians are so fond of.

I don't know much but I don't crimp anymore, I solder and shrink wrap. There are no quickie electrical connections anywhere inside.

 

[1 Wild R/T]

It continues to amaze me how many people experience repeated failures of the MP/Chrysler Electronic Ignition & yet insist on still using it.... Throw that thing away before it strands you in BFE....

 

[turbine68rt]

I think you might have some funky connections in the bulkhead connector.

I was thinking the same thing since chasing a random stalling issue for over a year. Ran perfect then suddenly felt like you just turned the key off. Turned out to be one connection in the main engine harness. Heavier gauge black wire that went to the battery side of the alternator. Replaced the female connector, block, and main harness and not one issue since then.

 

[Kern Dog]

It continues to amaze me how many people experience repeated failures of the MP/Chrysler Electronic Ignition & yet insist on still using it.... Throw that thing away before it strands you in BFE....

The stock system in my 75 Power Wagon is reliable, so is the one in Jigsaw but both of them have original Mopar built distributors, not aftermarket replicas. This is why I've wondered if the guts in mine here are just ****. I have swapped distributors and had it not fire, then get pissed off and walk away...only to come back in a few minutes and have it start just fine.
I'd embrace an MSD system if I could hide that huge ugly control box. I'd want vacuum advance too. I know that there isn't any power to be gained from ignition but reliability sure would be good.
I'm trying to recall what parts are in place that have been here from 2001 when I converted to electronic ignition.
I've changed every electrical part except the distributor, so to speak. I have pulled this one (During a NO spark episode) to use another, then just to confirm it is bad before tossing it ... I tried it again and it worked.
The same thing has happened with other components. I have had a Chrome ECM for maybe 10-12 years...

The other day during the A/C stuff, after it stalled, I swapped in another ECM and it started.
It is really weird for the car to run fine, sit a few minutes then get no spark upon a restart.
It also is strange to have it sit after a NO start and then just fire up as if nothing was wrong 5 minutes prior without making any more changes.
I could understand a situation where electrical parts got hot and needed to cool down but what about those cold starts after sitting for weeks?
This is really strange.
Sure, I could just keep replacing parts but I want to know what is really causing this. When I change a part and it starts, I thing that it was THAT part to blame but THAT part seems to work in the other cars.

 

[kiwigtx]

Throw that thing away before it strands you in BFE....

The only place you can get to without a map.

 

[kiwigtx]

The stock system in my 75 Power Wagon is reliable, so is the one in Jigsaw but both of them have original Mopar built distributors, not aftermarket replicas. This is why I've wondered if the guts in mine here are just ****. I have swapped distributors and had it not fire, then get pissed off and walk away...only to come back in a few minutes and have it start just fine.
I'd embrace an MSD system if I could hide that huge ugly control box. I'd want vacuum advance too. I know that there isn't any power to be gained from ignition but reliability sure would be good.
I'm trying to recall what parts are in place that have been here from 2001 when I converted to electronic ignition.
I've changed every electrical part except the distributor, so to speak. I have pulled this one (During a NO spark episode) to use another, then just to confirm it is bad before tossing it ... I tried it again and it worked.
The same thing has happened with other components. I have had a Chrome ECM for maybe 10-12 years...

View attachment 1633411

The other day during the A/C stuff, after it stalled, I swapped in another ECM and it started.
It is really weird for the car to run fine, sit a few minutes then get no spark upon a restart.
It also is strange to have it sit after a NO start and then just fire up as if nothing was wrong 5 minutes prior without making any more changes.
I could understand a situation where electrical parts got hot and needed to cool down but what about those cold starts after sitting for weeks?
This is really strange.
Sure, I could just keep replacing parts but I want to know what is really causing this. When I change a part and it starts, I thing that it was THAT part to blame but THAT part seems to work in the other cars.

What resistance is the ballast resistor - while you are running a chrome box?

Also, have you checked if the chrome box is hot to the touch when the engine cuts out?

 

[Kern Dog]

I have not checked the BR resistance. I have had a few different ones over the years. This one was shipped with the MSD Blaster 2 coil I had for awhile. I do not know the resistance of any of them. I did have this happen once....

The ECM has never been unusually hot to the touch, nor has the potting compound in the back ever melted out.

 

[Kern Dog]

SIX hundred bucks ??? Plus, that is an LA spec vacuum can. B/RB vacuum cans are on the other side.

 

[kiwigtx]

I have not checked the BR resistance. I have had a few different ones over the years. This one was shipped with the MSD Blaster 2 coil I had for awhile. I do not know the resistance of any of them. I'll admit, I don't remember how to do that. I did have this happen once....
View attachment 1633413

The ECM has never been unusually hot to the touch, nor has the potting compound in the back ever melted out.

That resistor looks poked. (that's Kiwi for broken)

 

[kiwigtx]

View attachment 1633414

SIX hundred bucks ???

That's cheap.....when you see how much an OE clutch switch is for a '70 car.

 

[HEMIB]

Try running a black gnd wire directly from the battery negative to a clean part of the ECU case where the unit screws to the firewall make sure the connection point is clean

 

[Kern Dog]

You mean run a wire all the way back here?

I have a ground on the ECM standoff bracket....

It attaches to the rearmost intake bolt. I've even grounded it to other points on the firewall.
Aside from everything else, what I am wondering is....what can work fine then suddenly NOT work, then work again without touching it?
That seems like a riddle, I know. I mention it because that scenario has occurred.
I've always been able to get it started eventually. It has never failed me on a road trip. I do carry spare parts with me.

 

[451Mopar]

You could try "Two battery" troubleshooting.
Disconnect the coil and ECU from the cars power and connect another battery positive to just the ignition ECU, coil (use ballast resistor if you want), and the negative to the engine block and ECU. Then use the original battery to crank the engine and see if the car starts/runs.

If it starts / runs the ignition is not the problem. Start looking at power to the ignition, and anything connected to ignition power like the alternator field power, or regulator, or electric choke and such. Also, check voltage from block the battery negative on the battery cranking the car. Ideally there should be no voltage when cranking, but this is load checking the ground cable and connections for resistance

If it won't start then problem is in the ignition

 

[HEMIB]

Could be intermittant engine to frame ground i am attempting to rule out 1 wire at a time there is only a few it has to be 1 if you have changed the distributor ,coil & resistor there must be something else when it wont start have you tried the coil lead to gnd to see if it flashing

 

[Kern Dog]

You could try "Two battery" troubleshooting.
Disconnect the coil and ECU from the cars power and connect another battery positive to just the ignition ECU, coil (use ballast resistor if you want), and the negative to the engine block and ECU. Then use the original battery to crank the engine and see if the car starts/runs.

This an interesting idea. Running power to the coil is easy but what about the ECU? It is a 5 pin plug that uses 4 of the pins. Would I need to modify a plug cut from a spare harness?

If it starts / runs the ignition is not the problem. Start looking at power to the ignition, and anything connected to ignition power like the alternator field power, or regulator, or electric choke and such. Also, check voltage from block the battery negative on the battery cranking the car. Ideally there should be no voltage when cranking, but this is load checking the ground cable and connections for resistance

If it won't start then problem is in the ignition

I forgot to mention....Sometimes during the NO spark, it feels like the engine wants to fire as I rotate the key back to lock. This is why I unplugged the stock one and tried another ignition switch harness....with no change.

Could be intermittant engine to frame ground i am attempting to rule out 1 wire at a time there is only a few it has to be 1 if you have changed the distributor ,coil & resistor there must be something else when it wont start have you tried the coil lead to gnd to see if it flashing

I don't think that is it. I have the engine block grounded to the core support, to the firewall too. The battery negative cable goes forward from the trunk mounted battery forward and to the engine block as well.

 

[HEMIB]

The 2 battery is a good system for fault finding your second battery Gnd still connects to GND then disconnect the Yellow & blue from the resistor & tape up connect a wire from the battery positive to an on /off switch then connect to where you removed the blue wire from you may gey away with not using the yellow as the battery is only powering the ECU you will not get the voltage drop you would normally get when powering the ECU from the main starter battery ,i had a similrt problem where the car would not start when hot when i left the car then returned it would start because it was easier to crank & the battery voltage was higher ,i found the ECU did not operate correctly when the start voltage dropped to less than 10.8 volts when cranking if i jumped it with a fully charged battery it would start first kick.Has it ever stopped once running or is the problem only when trying to start .

 

[threewood]

Good ground at the ecu?
Ecu plug in good shape, female connections tight?