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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: Dave W on April 25, 2019, 04:38:10 pm

Title: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: Dave W on April 25, 2019, 04:38:10 pm

I have a 1978 chevy c10 2wd 305 2brl
It was sitting for a few years before I got it.
I changed the whole fuel system tank to carb
Got it running it seemed fine.
Now it starts fine when cold, if I shut it off after 5min
and try to restart it, forget it barely runs (rough) and black smoke
Comes from tail pipe.
Wasn't doing it before.
Any ideas??
Thank you in advance

Title: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: Dave W on April 25, 2019, 05:24:10 pm

I have a 78 2wd c10 v8 305 2brl. it sat for a few years before I got it.
I changed the whole fuel system tank to carb
Got it running, and it seemed fine.
Now it starts fine cold, it I shut it off after 5 minutes, and restart it
It barely runs and pours black smoke out the tailpipe.
Any ideas??
Thank you!!

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: bd on April 25, 2019, 11:11:28 pm

Did you replace the carburetor or overhaul it?  There could be some fine debris caught in the inlet seat that prevents proper sealing of the needle or the float level may be high.

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: Dave W on April 26, 2019, 04:29:37 am

Replaced it

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: Dave W on April 26, 2019, 06:35:24 am

Yes, the carburetor is new replaced.
Seemed fine a week ago.
Not sure if the choke is staying closed,
or something like that.
Any thoughts?

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: bd on April 26, 2019, 08:59:10 am

If you think it's the choke, remove the air cleaner when the symptoms arise and look to see whether the choke is open or closed.

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: JohnnyPopper on April 26, 2019, 03:45:27 pm

"it starts fine when it's cold"

What happens when you "don't" shut it down after 5 minutes? Does it reach operating temperature.

Pretty sure the choke is the culprit.

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: Dave W on April 27, 2019, 10:21:30 am

It stays running ok.
The choke seems open a 1/8 of the way, never half or fully open.

Title: Re: BLACK SMOKE AFTER WARM UP 1978 2wd chevy c10 V8 305 2brl
Post by: JohnnyPopper on April 29, 2019, 03:52:41 pm

Bet you burn tons of gasoline!

Need to fix your choke man.... It's easier than looks.

Do a search on this site, lots of threads  for manual, heat riser, and electric chokes.