Black smoke on start-up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevychic · 01-22-2004, 04:06 AM

Hey all,

For the last 3 weeks my truck has been blowing black smoke when I start it. It's just when I start it and not while idling or driving. I adjusted the carb over the weekend and I know I have it adjusted correctly. It was running a little rich before. I just changed the plugs today to have a somewhat fresh start with the newly adjusted carb.

It doesn't matter how warm the engine is, in fact, when it's cold, I don't notice any black smoke. But it doesn't happen ALL the time. Maybe 80% of the times I start it when it's warm.
Also when it does have black smoke, it's really stinky. It doesn't smell rich. It smells like something else is going on. The smell is kind of hard to explain. I guess the closest I can come is it smells like old burning grease. Not quite as bad as hot differential fluid but kind of similar...I think??

Another thing that might be worth noting is I have oil that comes out of the filler hole. I've replaced the PCV valve and checked the new one to make sure it was good and checked the breather hose for obstructions but all is clear.

Overall, it drives really good and has been very reliable lately. I just want to catch this problem before it gets worse and leaves me stranded someday....

Any clues?

Mike76251 · 01-22-2004, 04:27 AM

Too me,
That is your choke coming on.
You know............making the mixture rich (or too rich?)
You might try to back off the choke a little and see if it helps.
If it is running a little rich; that's better than running lean.

Moloko · 01-22-2004, 11:53 AM

Yeah, but running very rich can be very bad. Thats why I have to rebuild my Chevelle engine. I took the pistons out yesterday, or rather they fell out, since the cylinder walls were so washed with gas.

Prerunner1982 · 01-22-2004, 01:28 PM

ok, heather and myself discussed this last night.. whats with the oil coming out of the breather and pcv? i am having the same problem. and have replaced the pcv..... breather clogged maybe?

**swervin ervin** · 01-22-2004, 02:31 PM

The oil coming out of the breather is a sign of worn rings most of the time. It's called blow by. Does it blow oil out or just build up over a period of time? Does it smoke out of the valve cover breather?

Prerunner1982 · 01-22-2004, 02:46 PM

as far as mine, it appears to blow oil as it covers everything on both sides.. and yes it comes out the breather...

chevychic · 01-22-2004, 02:59 PM

mine blows oil too. Mainly on the side with the filler hole. I can't keep anything on that side of my engine compartment clean because of it.
I have a bit of seepage out of the breather hole that appears to be build up, but its blowing out of the filler hole.

*1FaastC10* · 01-22-2004, 06:02 PM

if you've literally got oil blowing out of the valve cover openings, to the point of oil all over everything on that side of the engine, it may be time to start saving for a new engine, or rebuild the one you have. do any of your mechanic buddies have an air compressor that you have access to? if so, get ahold of a leakdown tester, and run a leakdown test. that will tell you the quality of the ring seal. my guess is, its not healthy. it still may be healthy enough to run, and get you where you need to go reliably, just make sure to keep an eye on your oil level.

oh yeah, if you do decide to do any major work to the engine, please take lots of pics. there's nothing sexier than a woman grease covered and elbow deep in an engine.

01-22-2004, 04:06 AM	#1
chevychic Registered User Join Date: Oct 2002 Location: Chanhassen, MN Posts: 1,061	Black smoke on start-up Hey all, For the last 3 weeks my truck has been blowing black smoke when I start it. It's just when I start it and not while idling or driving. I adjusted the carb over the weekend and I know I have it adjusted correctly. It was running a little rich before. I just changed the plugs today to have a somewhat fresh start with the newly adjusted carb. It doesn't matter how warm the engine is, in fact, when it's cold, I don't notice any black smoke. But it doesn't happen ALL the time. Maybe 80% of the times I start it when it's warm. Also when it does have black smoke, it's really stinky. It doesn't smell rich. It smells like something else is going on. The smell is kind of hard to explain. I guess the closest I can come is it smells like old burning grease. Not quite as bad as hot differential fluid but kind of similar...I think?? Another thing that might be worth noting is I have oil that comes out of the filler hole. I've replaced the PCV valve and checked the new one to make sure it was good and checked the breather hose for obstructions but all is clear. Overall, it drives really good and has been very reliable lately. I just want to catch this problem before it gets worse and leaves me stranded someday.... Any clues? __________________ *ChevyChic* 86 Chevy K-10 If I can't be a good example, then I'll just have to be a horrible warning. "You're braver than you believe, and stronger than you seem, and smarter than you think" - Christopher Robin

01-22-2004, 11:53 AM	#3
Moloko Hoarding Rusty Objects Join Date: Aug 2002 Location: Slatington, PA Posts: 267	Yeah, but running very rich can be very bad. Thats why I have to rebuild my Chevelle engine. I took the pistons out yesterday, or rather they fell out, since the cylinder walls were so washed with gas. __________________ 1985 Chevrolet K20 Silverado 1994 GMC Yukon Follow me on Youtube! - http://www.youtube.com/user/FuelInjectionSucks

01-22-2004, 01:28 PM	#4
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	ok, heather and myself discussed this last night.. whats with the oil coming out of the breather and pcv? i am having the same problem. and have replaced the pcv..... breather clogged maybe? __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

01-22-2004, 02:31 PM	#5
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	The oil coming out of the breather is a sign of worn rings most of the time. It's called blow by. Does it blow oil out or just build up over a period of time? Does it smoke out of the valve cover breather? __________________ Mike 1985 Chevy C-10

01-22-2004, 02:46 PM	#6
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	as far as mine, it appears to blow oil as it covers everything on both sides.. and yes it comes out the breather... __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

01-22-2004, 04:27 AM	#2
Mike76251 Senior Member Join Date: Mar 2003 Posts: 2,499	Too me, That is your choke coming on. You know............making the mixture rich (or too rich?) You might try to back off the choke a little and see if it helps. If it is running a little rich; that's better than running lean.

01-22-2004, 02:59 PM	#7
chevychic Registered User Join Date: Oct 2002 Location: Chanhassen, MN Posts: 1,061	mine blows oil too. Mainly on the side with the filler hole. I can't keep anything on that side of my engine compartment clean because of it. I have a bit of seepage out of the breather hole that appears to be build up, but its blowing out of the filler hole. __________________ *ChevyChic* 86 Chevy K-10 If I can't be a good example, then I'll just have to be a horrible warning. "You're braver than you believe, and stronger than you seem, and smarter than you think" - Christopher Robin

01-22-2004, 06:02 PM	#8
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,399	if you've literally got oil blowing out of the valve cover openings, to the point of oil all over everything on that side of the engine, it may be time to start saving for a new engine, or rebuild the one you have. do any of your mechanic buddies have an air compressor that you have access to? if so, get ahold of a leakdown tester, and run a leakdown test. that will tell you the quality of the ring seal. my guess is, its not healthy. it still may be healthy enough to run, and get you where you need to go reliably, just make sure to keep an eye on your oil level. oh yeah, if you do decide to do any major work to the engine, please take lots of pics. there's nothing sexier than a woman grease covered and elbow deep in an engine.



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