i had noise on the crank sensor which would cause the scan tool to read a rpm signal but would not pulse injectors or the coils at times,about every 10 starts or so.
the noise was only during cranking mode,runnung signal was clean,after investigation the starter was the cause of the noise

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Got any captures of the starter system while cranking?  Just out of curiosity.

i have to dig in my files but i think i had some across the pos cable and ground they were noisy also if i find them i will post them

Thanks