intermittent no spark on any cylinders

Car and system:
bmw e30 325i 6 cyl 1989
Aftermarket ECU, wasted spark and sequential fuel.
3 channel ignitor module (7 pins: ground, 3 inputs from ECU & 3 outputs to coil)
Wasted spark system (4 pins: common +ve pin & 3 inputs from ignitor)
60-2 crank sesnor reluctor, single tooth hall cam sensor
ECU does not produce codes like an OEM one but I can log and watch various sensors.

Major Symptoms:
Engine stalls and wont restart, cranks fine. First time it wouldn’t start for a day. AT that time all I could test was that there was no spark on any cylinders as didn’t know how test anything else back then
Last time it wouldn’t restart for about a minute didn’t have a test light with me and by the time I got one it started fine.
The problem is very very intermittent and hard to replicate to test properly.

Minor Symptoms:
Engine stalls/cutouts periodically but will restart fine straight away

Have watched this video and now do have a test light and multimeter (no scope though) just waiting for the no spark while cranking to occur to do some proper checks with the fault present

I watched this video, at the end it says the control should have battery voltage not just the common feed. Is this correct? I only get battery voltage on 2 of the 4 pins with ignition on using a multimeter. Though test light does light up on all 4.


My testing with incandesce test light when the cranking but no spark issue is NOT present
- When cranking the 12V feed pin showed continuous light , the 3 controls pulse but extremely subtly not like the Subaru video (engine was in flood clear mode). its not distinctly different like the video says it should be but it stills runs when it displays this behaviour
- When idling I had a test light on the common feed to coil and the engine stalled (test light went out) and went back on about 1 or 2 seconds after the engine stopped. Engine was able to be restarted straight away. Does this suggest intermittently the 12V feed to coil is bad? Haven’t been lucky enough to verify this again.

Ignitor has been replaced, I know don’t be a parts guy but hadn’t heard of ScannerDanner back then  it did run trouble free for 2 months after replacing it.

logging with ECU shows that sensors all look normal, and there is a good crank signal

any advice would be great as im more of a mechanical guy, but slowly trying to understand

Do you have a scope available?
When you have loss of spark is there also a loss of injector pulse?

Unfortunately I don't have scope. The injectors still pulse

one question i have is that with ignition on (not cranking or running) should i get constant battery voltage on each of the 4 pins going to the coil? what does it mean if i dont?

oddly enough i only seem to be able to get it on 2 of 4 pins, the +12V feed and one of the control wires to the coil. i dont know if i'm doing it wrong (ive been probing the back of the connector pin, everything is plugged in) but it doesn't make sense that the control wires are different. note that this was the case when the issue was not present.

i can confirm the +12V ignition switch feed is intermittently dropping out. everything else on the circuit functions as per normal. whats the best way to tackle just trace back?

would i be looking for a bad connection or wire rather than a short?