No spark...

Prob a newer orange ecu I bet?

Since it failed with another ECU, maybe the problem was NOT the HEI module....

"Mopar original stuff"
This is a very fine system, generally trouble free.
In it's first iteration, this was a dual ballast system. The one side reduced the power to the ECU, and the other side reduced the power to the coil.
If either side fails, the sparks go away.
However, the power to the Dual-Ballast, takes a torturous path from the battery to get there. So you have to check every connection.
The circuit is from battery to the fusible link, to the Bulkhead connector to the amp-gauge, to the ignition switch, to past the #1 splice, and back under the hood thru that doggone Bulkhead connector again, then to the spade lugs on the resistor, out the resistors to the devices, and finally, the ECU gets grounded to the body, which ground then splits; part goes to the engine block, then out the negative cable back to the battery; and the other part goes to the body-ground cable and from there to the battery

Whereas the Coil gets it's ground, back at the ECU, thru the switching transistor, and from there thru the ECU case, and back to the body ground, lol.

By my count that is about 21 connections or more.
The only one you don't have to worry about is the #1 splice.
The thing is, from the #1 splice the blue wire splits off in at least three different directions. Coming from the Ignition switch it goes to feed the Dual ballast, and the electric choke, and the alternator.
And if your car has A/C I think it went to that system, and if a convertible top, it went there as well. But not to worry, that #1 splice is a welded brute that I have never seen make trouble.
However, if one of those circuits is sucking all the power, well then the coil gets what it gets. So I always keep that in mind.
However, the First and easiest place to go is to check the ECU ground path. That lil nugget has to have a nice clean and tight ground. Last time I checked, oh about 1999, lol, they were screwed onto the PAINTED firewall or apron with a special screw. Chances are after four or five decades, that factory screw is long gone, and has been substituted with whatever the PO found handy. So remove the ECU, clean the case and the mounting surfaces. Then find two STAR-loc-washers that are able to penetrate the paint and reattach the ECU good and tight. If a hole is stripped out STOP!
Either fix it, move the ECU, or use machine bolts and nuts. It's gotta be well grounded. The last thing you want is to be caught 1500 miles from home, with No spark, No tools, and in the rain, at night. You can fix it now or you can fix it later, or you can pay some country-bumpkin Chevy guy to tow it to his shop where he will tell you that your car needs 2 days of diagnostics which you then spend in a flea-bag Motel; to replace everything, cuz you know, what can you do about it.........
Yes I'm exaggerating, but you get the point.

You can prove your ground is no good just be jumpering the ECU case to anything nearby that you know is grounded, like the engine, or the alternator case, or you know...... the battery, lol.
I can tell you that maybe 9 times out of ten, yur gonna find spark rightaway, lol.

Good luck Mr. South Sweden.

It's a single resistor & I've put extra ground wire from the module to the engine, sharp starlock washers & all. I don't get spark fronm the coil.
& the module / ECU looks exactly like this, even with the text & is new:
(no AC & no conv top)
& if you re-read my original post there's a question at the end & I wonder if someone can messure & see if you get the same result?

Ok that is a Second generation 4-pin ECU, and the ballast is for the coil. It works in the exact same wiring harness, so long as the ballast connector has not been modified.
>To test the ballast; simply bypass it with a straight battery voltage to the coil +; It will handle this for testing purposes.
>To test the ECU, simply pull out the coil wire from the D-cap, and near-ground it. Then every time you turn the ignition key to "off", from "run", the Ecu should spark the coil one time.
> to test the pick-up, the reluctor gap ought to be in the range of .008 to .011, but I have seen engines running on anywhere from zero to .030. Then, again pull the center coil tower-wire out of the cap and near ground it. With the key on, and in "crank mode", there should be a stream of sparks jumping the gap.
You can even do this with the distributor out of the engine and laying on the fender, it does not need to be grounded, just spin the driveshaft in the normal direction, and watch for the sparks at the near-grounded coil wire.
> the Pick-Up coil is directional. there are, to my knowledge, at least three different pick-ups, one for CW rotating, one for CCW rotating and one for the early computerized system. Any one of them will spark in either direction, but if the wrong one is installed, the engine will not rev up properly.
The identifiers are the colors of the wires., they come in IIRC, orange, violet, and black. For a SBM you need the Orange one.
They all have the same coil resistance which is just a lil north of 300 ohms, IIRC.
>to check the power supply to the Ballast, take the supply wire off and plug a halogen headlight bulb in there and ground the other side of the bulb back to the battery negative. If the bulb shines brightly and nothing smokes under the dash, then change the ground wire to the engine block, if it still shines bright; then yur good to go. Watch-out!, the Halogen bulb gets very hot very fast and it does not like fingerprints, often burning out prematurely. The point is to not allow the bulb to set your car on fire.

BTW
When you measure the voltage at the coil negative, you have to disconnect the negative wire off the terminal, else it will be connected to the ECU transistor, and read wrong, for purposes of testing the coil.
With the coil out of circuit, the voltage at the negative will be a little lower than at the positive, the difference going to heating the internal transformer. The longer the voltage is applied, the hotter the coil will get and the lower the voltage at the coil negative will read. Eventually the coil-temp will stabilize, and so will the voltage drop.
AND
If you measure the voltage-drop thru the ballast, with the engine running, yur gonna find the voltage going into the resistor, to be whatever the alternator is sending, whereas the output will drop to 8 volts or less over time as the ballast heats up with the load applied. this is normal.
The coil gets full voltage during cranking and whenever the ballast is cold. This gives your cold engine some 60% more spark power to help light it off. But as the engine warms up, it is fine with 8 to nine volts, low-compression engines can get away with even less. I've seen a performance engine running just fine on 7 or even less volts. so don't sweat what you see, unless it's less than about 7 volts, in "run mode", on a hot ballast.

BTW-2
With the firewall-mounted resistor, use only a Mopar designated coil, which has no internal resistor. Do not use an off-Mopar coil, which may have internal resistors. The coils are usually marked something like;
"not for use with an external resistor" or
"use with external resistor"
If it's not marked, you'll have to figure it out. which is not hard. Just pull a few amps thru it and see how low, and how fast, the voltage drops. If it drops below 9 volts, (I'm guessing) then the coil has an internal resistor, doing the job of your firewall-mounted resistor, so either bypass your ballast or get a proper Mopar Coil.
Butum if the voltage-drop remains small, I'm guessing less than a half a volt, then she's ready to use on your Ballast-resistored car.

Moparbaker said:

It's a single resistor & I've put extra ground wire from the module to the engine, sharp starlock washers & all. I don't get spark fronm the coil.
& the module / ECU looks exactly like this, even with the text & is new:
(no AC & no conv top)
& if you re-read my original post there's a question at the end & I wonder if someone can messure & see if you get the same result?

View attachment 1716225609

Click to expand...

New overseas fake transistor ECU. Bad track record, yes "mopar Authorized: also! Skim this.

These are exactly what you need have one left. Need to get more made up

I ohm-measured two not connected modules / "ECU"'s; one original MoPar & one chinese (I think the chinese is called "Standard") & got these results:
Anybody else who's done it too & is bold enough to post it here?

Different ECU;s have different internals so really need to know whats in there.
IE