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post #1 of (permalink) Old 12-22-2002, 12:32 PM
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Pulled an Oil Covered Spark Plug = ?

I've been having problem's with my CJ backfiring. I have a chevy 350 in there, and I noticed that one of the header tubes was glowing red. I pulled the plug by that tube and it was wet covered in oil. I did not start this engine in about 3 weeks. I pulled one plug next to it and it was white and dry.

So what's the diagnosis? What do I do now?

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post #2 of (permalink) Old 12-22-2002, 01:22 PM
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Re: Pulled an Oil Covered Spark Plug = ?

is it wet oil? or just black?

oil in there is a bad sign, do a compression check to see what type of ring seal you have, if it reads low ad a squirt of oil and check it again and see if it increases.

if its not oily and just black it may be an intermittantly firing plug and its just fouled.

Id do the compression test first though

if you dont own a guage, you can try and borrow one, but they sell for $25-$100 autozone, Napa, Sears, I think even Walmart has them

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post #3 of (permalink) Old 12-22-2002, 03:29 PM
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Re: Pulled an Oil Covered Spark Plug = ?

It was wet and oily not just black. I borrowed a compression tester, I just haven't done it yet. I rubbed the end in my fingers and it left a few drops of oil.
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post #4 of (permalink) Old 12-22-2002, 03:38 PM
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Re: Pulled an Oil Covered Spark Plug = ?

1. IMHO the exaust valve's burnt.
2. Gasses on the power stroke are forced into the exhaust manifold.
3. There they ignite and heat up the maniforld.
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post #5 of (permalink) Old 12-22-2002, 05:36 PM
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Re: Pulled an Oil Covered Spark Plug = ?

Could be just the plug itself was defective - or the plug

Not firing for awhile will collect oil on it, and gum from
unburned fuel.
Try putting a new plug in it, and check or replace the plug
Since the rest of the cylinder is full of that crud, the
new plug may foul out too, maybe even several times until
the cylinder burns itself clean.

The red exhaust manifold is probably from just the unburned
fuel from that cylinder - the fuel passed on through the
cylinder into the exhaust manifold, then got ignited by the
hot gasses from the other cylinders.

A compression check right now will probably not be very
accurate, as all the crud built up inside will raise the
compression a little (it takes up space,) and the rings
probably aren't seated very well anymore because the unburned
fuel washed the oil off the rings, lowering compression.
You may want to check it, but don't condemn the engine just

Get that cylinder firing again for a few miles, then check
compression again. Hopefully you'll be pleasantly surprised
that it's fine.
Even if the compression is 0, that cylinder will still fire
enough to clean itself up so you can get a real reading.

Rebuilders make tons of $$$ due to misdiagnosis, they love
bad plug wires just for that reason.

If you put a new plug in and it starts firing, but then you
hear it foul again, misfiring - try the old tow truck driver's
trick - essentially the same thing as the county fair "spark
Simply pull the plug wire out of the cap about 1/4" and hold
it there a moment, creating an extra gap. You'll hear that
plug start firing again.
Keep doing that until that cylinder can run on it's own.
It takes a few minutes to burn off all the crud.

Let us know how it comes out - on this thread.
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post #6 of (permalink) Old 12-22-2002, 06:16 PM
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Re: Pulled an Oil Covered Spark Plug = ?

OK, I'll get a hold of new plugs and wires. Won't be soon, though, I do all of my work outside in my driveway, and the temps won't be this warm again for a while. I'll dig up this thread and give an update.

Thanks for the help
post #7 of (permalink) Old 12-23-2002, 01:39 AM
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Re: Pulled an Oil Covered Spark Plug = ?

Hmmm......I hadn't considered what RRich had to say. Makes sense. One other posiblilty for why the plug is fouling with oil: bad valve seals. Had this problem on a 1990 Olds Cutlass Calais with the 2.5L. After my wife scattered the engine, I rebuilt it and had a guy do the head. I sold it to my father, and it's burned a little oil in #1 ever since (#2 was the problem when the engine blew...ever seen a piston so badly cracked that it came out of the top of the engine when the head was pulled? all I can say is freaky!) It turned out the guy who did the head missed a seal. Not saying that is your problem, but something else to check.
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