Mopar ecm issues. Why wont they work?

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AJ,
Agree the transistor is merely an electronic switch version of the points. If you touch the coil neg terminal on a running engine, you will get a tingle you can do without....About 200-300v of EMF from the collapsing mag field of the coil.

So I am wondering if the trans case, usually the Collector on that type of trans, is connected to the coil neg, which would make the case 'hot' electrically, engine running.
 
pishta said:
Ditch and go Mallory. Ill pass up a 6AL box at a swap meet for $20 (Nah, Ill flip that SOB faster than a slap shot). Mallory may not be the highest performing but they are rock solid reliable.
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Pertonix III is even better when used as directed to the letter! JMO!
 
69moredoor said:
View attachment 1715891640 Thanks hops. will read that. To add confusion (before I read it). I played parts swap with the 79 d100
Two of the new ecus worked fine (did t try the third)
The hood one from the d100 (318)—older unit made in maylsia (see pic) worked in the aspen!
Retried the new ones and yup. Work in the d100 but not the aspen. So…new units work in 79 318
Old units only work in the 80 slant
how’s that for confusing
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Sounds like they are all good? Connection issue maybe?
 
halifaxhops said:
Sounds like they are all good? Connection issue maybe?
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my Milwaukee ratchet looked at me and said “cmon man not again, how many times we gonna swap pull swap pull”

I’ll follow that video and double check the grounding (even though I tried with a dedicated grounding wire)
 
Inspect the plug really well, does not take much to make a poor connection either. I will get crap about this but noticed some boxes the contact pins are just a bit smaller. To bad your not closer I would check them on the tester.
 
5 pin vs 4 pin? Just spit balling. Hoppy has testers to check them.
 
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Ok. Had a morning cup and ran out there after watching the videos
Video one tested just like the vid when unbolted
Took one of the “in the 79 good new units”
Sanded the backside of the ecm in case there was a clear coating
Took jumper wires
Used self tapping screws next to the bolt holes with one jumper wire in the bolt hole
A jumper wire from one screw to battery
Ran video two test. Grounded

fired her up and …nope. Dang it
Checked plug connector. With key forward the two left wires are hot
Left black and blue
 
Yeah, I've had to pinch the terminals in the plug on occasion so they grabbed the pin tighter.
 
What I'd do.........scare up a new replacement module connector pigtail. You can find them, NAPA, online, you'll have to look. Get some alligator clip leads. "Rig" and layout a whole test system. It's only 4 wires plus ground. Wire it all up "hot wire" and test it that way. Do not use a ballast. Don't leave the coil/ system powered up longer than you need to to test. And, I've done this will clip leads only, no connector
 
You need a coil, the ECU and the distributor

Lay it out on the bench. Follow the diagram. Find the two distributor pickup terminals on the ECU. Hook them to the distributor

Hook the ECU case to battery NEG

Coil does NOT need grounded

Distributor does NOT need grounded.

Hook coil + to the power lead terminal on the ECU. Get a clip lead hooked there and let dangle. This is your battery "hot" when you are ready

Hook something from coil "case" to a probe for testing spark.

Hook up your power clip lead. Twist the distributor shaft while holding the test probe near the coil tower. The thing should make sparks

If not, unhook distributor. Take first one, then the other pickup clip leads, and "tap tap" ground them at the battery connection. Coil should make 1 spark each time you do so.

If not, try another coil. If that does not fix it replace the ECU

IF you hook it all up and it WORKS, then there is something AFU in the car harness. SUSPECT a bad ECU connector OR a bad DISTRIBUTOR connector
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This is all you need to test the basics of the ignition. You can easily test the ballast separate. A battery, the ECU, distributor and a coil, and of course some test leads

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Below, the basic diagram for a 4 pin ECU

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Below, the wire for testing spark. I use my 12V test light. No, LOL the spark won't blow up the bulb

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Below, the ground connection. ALL you need is one wire from batt NEG to the ECU case

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Below, the two distributor connections. In the car these are polarity sensitive, but for testing does not matter

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Below, the coil NEG connection

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Below, battery PLUS connection, one wire to this terminal of ECU and jumpered over to + side of coil


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Below, all hooked up and ready to test (except for battery ground). Should produce sparks at least 3/8" and typically 1/2" long

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Below, distributor "one wire" test. I have removed the other distributor wire for simplicity. Take the bare connector end or this clip lead (the yellow) and with everything hooked up, ground it repeatedly. Each grounding should result in a spark (In this photo you need to hook up the ECU ground wire, I left it off for the photo)

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To try and unconfuse the last photo^^

1...What I am tapping with the yellow wire is the distributor "bare" terminal to the battery NEG. This should generate one spark "snap" each time. The unconnected terminal in the box CW from the yellow wire is the second dist. terminal, and not used in this test
2....The box shell must be grounded to battery NEG which I have left disconnected
3....Box top left terminal is 5th terminal and not used
4...Top right terminal GREEN wire goes to coil NEG
5...Box far right terminal RED goes to coil PLUS and to battery PLUS
7...Yellow clip on left coil is coil NEG that clip goes to the test lamp which is only used here as a test probe for spark at coil
 
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Great ideas. Here is anither one when the car is running start wiggling connections and see f it dies, same with the wiring, if so connection/wiring issue.
 
If you want me to check the boxes on the tester just send them to me and the rides. I really think you have some thing else going on and are getting tunnel vision on the ecu's If you have some dielectric compound use it on the plugs also.
 
69moredoor said:
…yeah I checked ..insulation Intact

pic

View attachment 1715892274
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Get a trailer harness terminal cleaner, then after shining up those, roll 'em tighter with mini needle-nose & tiny screwdriver. I can only imagine two reasons it would not run in the car, but start the truck.
1) The terminals are more snug in the tk, & the new ECU pins are undersized, thus only making contact in the tk.
2) The low-voltage limit for operation is higher in the new ECUs, & the cranking voltage is lower in the car than the tk., check them both.
3) Even if the new ECUs are for a 5-pin system w/a dual-ballast, it should start & run in a 4-pin car.
 
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