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I pulled my heads for bent valves but found cyl 3 to have major carbon buildup. Much more than any other cyl. Got it running yesterday. Vue uses coil pack for each bank. They cost $40 or so. Should I change the coil just cuz? How do I know if 1 cyl has weak spark? Something was going on in cyl 3. Cyl 3 is on right. Springs are removed. I was trying to show major crud on exh valves.
To me, looks like cylinder 3 is blowing oil; meaning it is getting past the piston rings.
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Is this Opel V6 an all aluminum alloy engine . . . ?
Iron block. Alum heads. MLS gaskets. Cyl walls looked fine. Seems to run ok now. With new valves and cleaned head of course. How long will it run “ok” before oil fouling might be noticeable? If that cyl does have ring issues?
Did you replace valve seals? Maybe that’s what was leaking.
Checking the spark plug should give a read on current oil burning.
I agree.
Besides which OK4450 and I have both been posting here for many years and I’ve come to consider him the most knowledgeable engine guy who ever posted to a forum. I’ve learned a great deal from him.
Compare each of the spark plug’s visible spark. If number 3 is redder, or not as bright as the other’s, that’s a clue. My guess, this isn’t a weak spark problem. But easy enough to do the visible spark test.
@the_same_mountainbike, you’re too kind. I just finished a glass of Pecan Moonshine and feel a tad embarassed even after consuming that.
Back to the jug I guess… ;–)
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motor has run for 30 min total? i drove it up/down the block. smooth and quiet due to all new exhaust. tabs expired in april. been sitting in garage since feb. need to run down to dmv. than maybe drive it a bit. you have to pull intake to reach coil packs. it uses the 3+ coil pack on top of plugs. very annoying to do a plug change.
It seems like it would still be pretty easy to do a visible spark test on that configuration, once you get access to that part in the photo above. Once you remove it from the installed plugs, you could just install 3 spare plugs into it, figure out a way to ground the part of the plugs that need grounding, while a helper cranks the engine. You’d see sparks on all three plug tips occurring at slightly different times as the engine cranks wouldn’t you? Makes it easy to compare them to each other too, for spark quality.
Odds are the spark is not weak. It’s a matter of weak combustion in the chamber due to lowered compression.
LOL, I understand you can run diesels on that stuff… 
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It’s definitely not like the regular shine which is smooth as silk. A local guy once in a blue moon churns some of this stuff out in very small quantities. It sure eases the back pain while sitting in a chair at the PC.
i go to an english website devoted to vauxhall/omega cars which use this series motor. most all agree that ring issues are very rare. is a ring a ring? will a compression ring fail on 1 piston and the oil control ring also fail? yes rings do break. or wear. thats life. would my new headgaskets help the compression issue if there is one? suppose i could do a compression test now. after i just pulled the heads.
Not on old, high mileage, and/or neglected or abused engines.
Yes. Oil rings are not designed to withstand the pressures of the combustion process. Only the compression rings are. Oil rings are simply to wipe off excess oil.
Nope, not if the rings and/or cylinders are shot.
If you can figure out how to do a compression test without the heads, please post the protocol. It’d definitely be a new one on me.
the_same-mountainbike is dead-on with all points.
There’s only one thing I can add and it’s something I’ve seen a few times. You can have great compression (say 190 PSI) and still have that cylinder blowing oil past the rings. The 2 compression rings are fine; it’s the oil control (or wiper) ring that is the problem. The majority of engines I’ve been into almost always had oil control ring issues. Those are the ones that take a bit of chiseling with a screwdriver to get the rings out of the piston groove.
Subarus were exceptionally prone to this.
When the piston is on the downstroke the oil wiper ring is supposed to scrape the oil off. The rings often seize for whatever reason (overheating, lack of oil changes, etc, etc) and they do not “breathe” so to speak. This means a lot of oil is left on the cylinder bore and it works its way into the combustion chamber.