No spark from L67 3800 V6

[sdryluth]

I swapped an L67 3800 from a 2000 Pontiac Bonneville SSEI into a 1984 Mazda RX7. It's fitted to a manual transmission, no air conditioning, no egr, and no evap so I trimmed down the Bonneville engine wiring harness to only have the minimum wires required for engine control, and I am running a random 6 fuse 6 relay box I got from ebay.

I got everything all hooked up and ready to go, but it wouldn't start. Some diagnosing has revealed that there is no spark on any cylinder. It is my understanding that on cranking the ICM is in full control of spark stuff, and in fact it should have spark at cranking even with no PCM at all because the PCM doesn't take over spark until its running.

My initial guess was it was just an issue with my wiring work, so I pulled up this diagram of the wires going into the ICM connector.

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I verified we have power on pin P, and ground on pin K and M. I only have a one lead scope so I couldn't scope out both the crank 18x and crank sync signals on pins G and H at the same time, but individually they look at least reasonable. I can see the sync signal has three progressively larger windows and the 18x signal looks like a bunch of mostly even blips up and down very quickly.

I figured that with these things it should be capable of getting spark, right? So I swapped in a known good ICM and set of coils packs assuming mine were bad. It didn't fix the issue, still no spark.

Any ideas on what I am missing here?

[Vbb1994]

Vats?

[fst100]

does everything else work, such as fuel pump priming? what happens when you try and turn to run, does it crank at all?

[sdryluth]

I think VATS on these things just cuts fuel, but I am not totally sure on that. In theory it is disabled as well.

The fuel pump primes with key on and I hear the injectors click. It cranks, it just never actually produces any spark. On VCM Scanner I can see the MAF reading change when cranking and the tach reads correctly which I think means the ICM must be sending the 3x and 18x signals back to the ECM?

[SiriusC1024]

Are you sure it's getting a 3x sync pulse from the CKP (wire H)? Not the 3x ref signal sent out by the ICM (wire D). That ref signal is generated by the ICM itself.

ICM disables spark if there is no sync at startup.

[fst100]

just curious, did you replace or remove the harmonic balancer to replace the crank sensor?

[sdryluth]

Well I found out that the "known good" ICM that I swapped in was also bad. Put in a new unit from the parts store and its running nicely now.