Fried ECM

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Mattax said:
Sounds like you're making some progress.
Start side is also coil side, so when the key is in run and the points are closed then current will be running through the coil.
With an ECU hooked up instead of points, current will flow through the coil when the key is on.
If you unplugged the ECU's pentagram shaped connector, then no current can flow through the coil.

Lets go over the voltage drop testing.
Key off, nothing turned on, door shut so the dome light is off, no current flows.
Checking for voltage simply shows which wires are hot.
Lets say the battery is fully charged and voltage from positive to ground is 12.8 volts.
View attachment 1715398025

Same situation, turn the key on with the ECU disconnected.
View attachment 1715398027
Why are there voltage drops?
Why might there be a little ammeter movement?

Its because the voltage regulator is seeing less than 14 Volts, so its allowing current to flow through the alternator's rotor.
The ammeter movement will be very small because its only around 2 amps. A little more or less depending on which alternator is installed.

The voltage drop illustrated in this example shows resistance in every push type connection that causes a 0.1 Volt drop for every 2 amps.
Think about that.

Voltage drops where current flows through resistance.
Same drawing with arrows showing flow path.
View attachment 1715398030

Increase the current through a resistance and there will be more voltage loss.

The dash ammeter scale goes from 40 amps discharge to 40 amps charging.
Its good enough to see movement in the needle with 4 or 5 amps flowing through.
Notice it is positioned only to show battery charging or discharging, not alternator output.
Click to expand...

Thanks for all your effort, and all this information. I did pick up a NAPA ignition, switch,as I have no faith in the AZ parts that are in there now. Will be checking voltage as I go, at the old switch, and the new one. Also the amp meter has been bypassed. The engine currently runs. I put the Pertronics dist. back in yesterday, just to get the car back into the garage as it died in the road at the bottom of my uphill driveway.
 
67Dart273 said:
You can easily "hot wire" the ignition to see if it will run. One way is to pull the blue field wire off the alternator and run battery power TO it. It should be spliced into the ignition. Another place is to figure a way to jumper power into the ballast where it is jumpered together. That is, two of the 4 ballast terminals should be jumpered together.

So far as losing voltage, the functional path is battery.........starter relay "big stud", fuse link, through the bulkhhead on the big red ammeter wire

Through the ammeter, out the blg black ammeter wire, the welded splice, branch offf to the fuse panel "hot" bus and to the igntion switch.

Through the switch, out on "ignition run" usually dark blue, back out through the bulkead, and at some point branch off and feed the ignition system, the VR, some smog equipment if used, and the alternator field

So the main points to check are the big red and big black going through the bulkhead, the ignition switch and it's connector, and the dark blue feeding back out into the engine bay through the bulkhead
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Thank you Sir.
 
wot440 said:
Thanks for all your effort, and all this information. I did pick up a NAPA ignition, switch,as I have no faith in the AZ parts that are in there now. Will be checking voltage as I go, at the old switch, and the new one. Also the amp meter has been bypassed. The engine currently runs. I put the Pertronics dist. back in yesterday, just to get the car back into the garage as it died in the road at the bottom of my uphill driveway.
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Good chance that bypass is part of, if not all of the problem. Not needed unless there are more mods you haven't mentioned like EFI and electric fans. I'd put it back to stock and then troubleshoot. If there is a bad bulkhead connector, you can always run a parallel wire.
If you troubleshoot the way it is, you'll have to draw it out the way it is. Then you can figure it out. Same methods as Del and I have been describing, but applied to the flow paths on your car.
 
Mattax said:
Good chance that bypass is part of, if not all of the problem. Not needed unless there are more mods you haven't mentioned like EFI and electric fans. I'd put it back to stock and then troubleshoot. If there is a bad bulkhead connector, you can always run a parallel wire.
If you troubleshoot the way it is, you'll have to draw it out the way it is. Then you can figure it out. Same methods as Del and I have been describing, but applied to the flow paths on your car.
Click to expand...

OK thanks.
I did the amp meter(dummy light) bypass as suggested in the C body forum,(basically just removing the two wires from the meter and making them a connection) as they are said to be a weak link and a fire hazard. Easy enough to put back if needed.
I do not have any other mods. No fans, EFI or other.
 
wot440 said:
I did the amp meter(dummy light) bypass as suggested in the C body forum,(basically just removing the two wires from the meter and making them a connection) as they are said to be a weak link and a fire hazard. Easy enough to put back if needed.
I do not have any other mods. No fans, EFI or other.
Click to expand...
OK. It's a straight bypass. There's many versions of this supposed improvement. It leaves you blind but at least there is not some weird routing and hacked wired.
The ammeter is no more fire hazzard than any of the rest of the feed/charging circuit. The current flows through a big shunt plate which the terminal studs are pressed into. If the studs are not loose (which does occassionally happen) the will be no resistance to flow internally. If either stud is loose, don't use it. That's a stiuation where bypassing makes sense.
Do check the connections of both ring terminals. If some wire strands are broken, insulation shows heating, or any other symptom of a poor connection, that needs to be fixed.

wot440 said:
My plan for today is to finish unraveling fifty years of electrical tape and expose every wire and connection in the engine compartment. Then one by one inspect clean and check resistance and voltage for each. Once this is done I will move to the other side of the bulk head connector and do the same.
Click to expand...
With the bulkhead connector removed, the only thing to be learned from voltage reading is that the wire is connected to the battery (or not).
No current is flowing, therefore voltage doesn't drop.
Voltage drops can only be checked when current is flowing thorugh the wire.

Safer to disconnect the battery when removing connectors. If any of the metal terminals touches ground, the battery will try to discharge through it!
Think about how many amps that battery can dump through a wire. There's a fusible link somewhere on wire from the battery to the bulkhead. There's no point in testing accidently!
If you can measure resistance in any circuit run, there's a problem in it. But the ohmeter only sends a small current to make a measurement. So its possible to have voltage drops in circuits even when the ohmeter shows good continuity.
Visual checks are good thing to do. You can see corrosion, broken strands, overheated or chafed insulation, etc. Once you have the bulkhead disconnected you will be able to see the male terminals. And if you want, you can release and push out the female terminals one at a time.

question on the main harness plug on firewall

Lost all power need help


I noticed the starter relay to starter wires are fifty years old and are not in the greatest shape, so those will be replaced but not until the problem is found.
Click to expand...
Should be one wire from the starter relay to the starter. Agree its not related to dying while running.


wot440 said:
Single ballast is what was existing. 68' Newport.
Click to expand...
The ballast should .5 to .7 ohms for Chrysler ECU and a typical stock coil. You had some with 1.5 Ohms ? Could be a problem.
With points check the '68 FSM, I think its about the same.
Pertronix - need to see what Pertonix recommends, prob varies with coil. BUT Pertronix may regulate current to coil, in which case may need to jumper the ballast. @halifaxhops may know that.

Mattax said:
Do you have a spark tester?
Need that and a voltmeter with some aligator clips.
With those you can determine if it is, or is not, an ignition issue or ignition power issue.
Click to expand...
The spark tester plugs into a spark plug wire and the other end on a spark plug. Then you'll know for sure if its ignition related.

Other possibilities
Mattax said:
Timing? RPMs?
Choke not pulling off?
Click to expand...
Choke being the most likely. Although IIRC you posted manual choke.

67Dart273 said:
Maybe a bad ignition switch.............Those should all be dead, key off
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Yes. I'm still not sure this is the correct switch for the model and year.
Before installing the new switch, take the ohmeter and check the output terminals in run, off, and start positions. Make sure they match the wiring for your connector.
Mattax said:
One possibility to look out for on the ignition switch is its for a different year/model.
They shouldn't physically interchange but maybe they can????
From 68 to 69 Abodies the Ignition 2, Accessory, and Start wires connect to different switch terminals.

Why do 68 & 69 dart iginition switches have different # ground plug ins?
[SOLD] - nos mopar ignition switch
Click to expand...
 
Yes petronix needs the ballast jumped and also a electronic coil. Will not work well under 12VDC
 
Not sure. Same as last time. Fired up, sounded strong, then died after a minute. I am going to try an HEI system, as I am all out of ideas and patience with this set up.
 
I would find out why it is shorting them out before you fry HEI modules. Prob something stupid.
 
So anyways I figured it 's time to bring this to date. Ended up buying a new, stock points distributor from rock auto. With no luck tracking down the issue, and no luck with the HEI system. I decided to go back to basic OEM style ignition system. The new dist. came with new cap rotor points and condenser. Installed new spark plug wires and she fired up first try with a small adj. for timing. This is what I installed.
More Information for CARDONE 843816
Next will be to road test, not today as it is raining. Bitter sweet solution, with no real answer to the original question. I'm sure if one of you guy's were here. you've figured it out in short order.
Thanks everyone once again for the support.
 
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Thanks for the update.
Points work fine and with a big block its not that hard to access the distributor.
If you're drag racing, a dual point is an advantage in the upper rpms. Not sure there's much advantage otherwise, even at highway speeds.

Checking the '68 Plymouth shop manual -
all engines used the same ballast resistor, should be 0.5 to 0.6 ohms (part # 2095501).
Two different coils were used.
With automatic transmission, primary resistance should be 1.65 to 1.79 ohms
With manual transmission, primary resistance should be 1.41 to 1.55 ohms

If using a coil with lower resistance, then the higher resistance ballast mentioned earlier in the thread is probably OK.
But if using coils with the resistance in the 1.5 to 1.7 ohm range, try to find a ballast resistor with the recomended .5 to .6 ohms.
 
Another tidbit - that's probably got a late 60s timing curve in it (for Clean Air Package)
If so, then it doesn't need much timing at idle. Plymouth suggested 7.5* at 650 rpm on the std perf. 440 with automatic.
If you try more inital advance, it might ping at either part throttle or full throttle once the engine is fully warmed up. If so, back it down again.
If not, you can try a little more again. But no more than 12-14* at 650 rpm should be needed on a stock engine.
 
Mattax said:
Thanks for the update.
Points work fine and with a big block its not that hard to access the distributor.
If you're drag racing, a dual point is an advantage in the upper rpms. Not sure there's much advantage otherwise, even at highway speeds.

Checking the '68 Plymouth shop manual -
all engines used the same ballast resistor, should be 0.5 to 0.6 ohms (part # 2095501).
Two different coils were used.
With automatic transmission, primary resistance should be 1.65 to 1.79 ohms
With manual transmission, primary resistance should be 1.41 to 1.55 ohms

If using a coil with lower resistance, then the higher resistance ballast mentioned earlier in the thread is probably OK.
But if using coils with the resistance in the 1.5 to 1.7 ohm range, try to find a ballast resistor with the recomended .5 to .6 ohms.
Click to expand...

I will have to look into this to make sure I have the correct match up, and timing.Thank you sir.
 
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Wanted to share what you all been helping with. My 68'. Thanks again for your support.


IMG_20191020_061109.jpg

IMG_20191020_061126.jpg
 
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I guess the first question we need to ask is year, make, and model with photos to go along with it.
 
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