STUMPED! 1988 Merc Inline 6 No trigger to Switchbox Cylinder #4

[chuckb]

Thanks in advance for any responses………

1988 Merc Straight 6. Was lacking power and skipping like a you know what. Determined that it was not getting spark on certain even and odd cylinders. Meaning toasted switch packs. Replaced both switch packs and now had good spark on all but cylinder #4.

I am a -once upon a time- electronics engineer so understanding the ignition troubleshooting guides is no problem. Read the inputs to the switchboxes and #4 was not getting the necessary >1 VDC signal. Lifted the input and still no signal. Swapped #4 and #6 inputs and the problem moved along with it. This proved that there was possibly a problem with the trigger assembly. Also ruled out coils, bad wires, etc. Everything (except trigger #4) measured out correctly per the CDI guide.

http://www.cdielectronics.com/cdi-a...r=115&search_sender=partApplicationSearchForm

Ok. So I finally changed out the trigger and still no #4. Swapped out the stator and still no trigger on #4! Only thing in the chain that’s remaining is the flywheel but I highly doubt that failed. Checked all the magnets and they are in place and secure.

Any ideas as to what’s going on here? My grandkids will be happy to get back on the lake.

Happy 4[SUP]th[/SUP]……………

 

[fastjeff]

Are you sure it's getting spark? (You might have water getting in there and shorting out the plug, which resembles a no-spark condition.) Hard to believe only # 4 won't spark.

Jeff

 

[chuckb]

Are you sure it's getting spark? (You might have water getting in there and shorting out the plug, which resembles a no-spark condition.) Hard to believe only # 4 won't spark.

Jeff

Jeff, all the plugs are out. My problem is no trigger signal at power pack cylinder #4 input. Its not a plug, coil, wires, compression, fuel issue.