Think I found the " Miss "

Lockman

Appreciate and Admire other' s Knowledge
:unsure: I pulled all of my 1K mile spark plugs ( AC R45TSX's ) . All look pretty good white / light tan , Except for # 6 . its slightly flack , black soot. I ordered NGK 6630 UR4's , per Earl Brown's reccomendations. Any way , I'll do a compression check , but I'm pretty sure that it's gonna be Ok? I did notice what I think is a " weak " Spark at & 6 . Coil pak resistance , At he towers , is within spec. ? I've read that does not mean much because that could change under load ?
Any Idea's would be appreciated.
 

Lockman

Appreciate and Admire other' s Knowledge
Thanks Chuck, I don't think so..... But I have another used one, so I'll take this one out , look it over real good, and let you know.
thanks for somethin' to look for.
 

Jerryl

Tall Chinese Guy
Yes, its typically #6, the hardest one to get to in every way! I call it the b**** cylinder, because it is! Lol
 

Jerryl

Tall Chinese Guy
.30 ......The TSM says .60 ! :eek: , but I always follow what I read from you guys.
Try this if the plug is fuel fouled.

Measure ignition wire resistance, and verify the crimps at the connectors.

Close the gap to 0.025"
Swap the plug wires at the coil between #6 and opposite tower. See the the issue follows the original #6 tower.

Make sure voltage is >13.5 running, and measure/test voltage drop at the ignition module feed wires.
 

Lockman

Appreciate and Admire other' s Knowledge
Ok Jerryl, the plug is sooty, flaky black. Not really fuel fouled, more like incomplete burn ? The wires are newer MD? from Kirbins I believe.
I'll check for resistance , tonite.
 

Lockman

Appreciate and Admire other' s Knowledge
Hello there Earl Brown, Jerryl, & Chuck ,
I checked around the towers of the coil pack, & the thing looks new ! I 've got NGK 6630 UR4 's going in tonight. I've also got 1 K MSD 8.5 wires in there , When I check resistance on. # 6 wire, it's the longest , & has a resistance of .12 ohms . The other's are around .10. I'm doing a compression check tonight, while I've got the old plug's out.
I also have A new AC Delco CCCI D552 , GM #12353801 that's made in China ?
Should I swap out my original unit with this & keep it as a spare ?
Are the UR4's hot enough for my unique DD. My Buick Engine is in my Jeep :cool:?
 
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Anthony P

sharing knowledge with those who care to listen
Hi Richie, I wish GM never published that coilpak resistance value range for indication of OK - good to go. As Chuck noted, coilpak & ign module can behave differently when hot and can certainly behave differently under load. Also, odd spark conditions exhibit if there is something amiss with the charging system (battery & alternator) whereas system voltage is less. bench testing known good coilpaks and ign modules at 12.6 VDC using just a battery and Casper's tester would have you believe all coilpaks were defective. However, adding a charger to raise the voltage to 14.1 VDC, the coilpaks all tested perfectly.

I covered this scenario in this thread: help interpreting electric arc variations using Casper's C3I to test coilpaks & ignition modules

that Casper's tester is invaluable. John has it currently on sale for 11 more days...maybe something nice to add to your toolbox. it's the only way to test these things. CCCI Ignition Simulator

On the coilpak, cylinders 3 and 6 are together. it's a waste-spark system. but you noted that #3, like the others looked fine. only #6 was running rich or was fouled. so that should eliminate any issues with the coilpak & ign module.

Years ago, Mr. Clark flowed intake manifolds.interesting numbers

for the hot air's, on a stock intake, it was #4 that flowed 14 - 19 percent less than the others. #6 flowed the same as #2; and were +- 4cfm to #1, #3 and #5. So I don't think it's an air volume (or lack thereof) causing #6 rich fouling.

a compression test is OK but a leak down test would tell more. these folks already covered it...

Compression test PSI

Help with compression test #’s and spark plug reading

if you don't like the harborfreight leak down tester, there are plenty of others on Summit, Amazon, etc. I use the total seal version.

You may find after all this diagnosing and testing that #6 just runs that way. And the suggestions from Jerryl and Earl and Chuck are your key.
 
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No disintegrations

Well-Known Member
Ok Jerryl, the plug is sooty, flaky black. Not really fuel fouled, more like incomplete burn ? The wires are newer MD? from Kirbins I believe.
I'll check for resistance , tonite.
Rich would be dark brown. After that pig rich will be sooty black. Shiny black or greasy indicates oil burning. I do think sometimes very minor oil burning can manifest as sooty black on the plug.
You could also move that fuel injector to a different spot and see if the problem follows it.
 

Lockman

Appreciate and Admire other' s Knowledge
Thanks for the reply. Just did compression check. All 6 were 120 after 4 cranks. Put new NGK UR4's in. Started right up warm it up on a regular drive around , then got into it , 0 to 60. No hesitation & I noticed a difference . Tomorrow , after back and forth to work , I'll pull # 6 and see what it looks like.
 

Lockman

Appreciate and Admire other' s Knowledge
So .......After 50 miles on the new NGK UR4's , gaped at 25 , I pulled # 6 & it reads like the other 5 . And............. the ' Flat Spot ' I was noticing @ around 2500 RPM , going from 2nd to 3rd , seems to be gone :cool:
I really think that closed gap & hotter plug has made a big difference. Who Knew ???? Well, Jerryl did , Many Thanks .
 

Anthony P

sharing knowledge with those who care to listen
good to hear Richie. yes, Jerryl is a true asset to this forum. with all the ideas tossed around, I too was wondering about a "fat" injector like No disintegrations noted above. And I thought of the possibility of oil seepage past the intake valve seal. good to be aware of all these possibilities - smart to begin with simple stuff like you did.
 
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