Almost have this truck 100% ready for plowing snow this winter and with it already starting I need some last minute help with bouncing a few ideas off you guys.

I have black smoke coming out of the tailpipe and seemingly low power.

I have replaced the rotor, cap, plug wires, and plugs and attempted to clean everything on the outside of the carb.

Could this be my choke not pulling off? The truck seems to not smoke black at first, then after 10 min starts emitting a little bit of black smoke into the exhaust.

 

Anyone? Bueller?

 

Black smoke is a symptom of a too rich mixture so it could be a choke problem or a mixture problem. Just look down the throat to see if the choke is opening fully once it is warmed up. How is the power when cold?

 

My brother's 87 360 was doing that. It's got pollution control on it, and not sure if that's part of it, but there are flaps in the fresh air intakes that are vacuum controlled. We weren't sure if we could just unplug the vacuum hoses and they would stay open, so left them alone and popped the air filter cover on upside down so more fresh air can get to it. That seemed to solve the problem. It gained more HP and more MPG. That was up in higher altitude, when we got back to florida, we had to put the cover back on right cause it was getting too much air.

Just a thought if nothing else seems to work. Might at least get you through this winter.

 

check your air cleaner

 

Since you say it's OK until it warms up I'd give it a 99.99% probability that your choke isn't pulling all the way off when it's warmed up. A dirty air filter will contribute to the problem.


As to the flapper inside the snorkel, they will stay open if you disconnect the vacuum lines. The little cannister on the outside of the snorkel is a thermostat which holds the door open until the temperature drops below 50 degrees, then it will allow vacuum to close the flap. There is a temp sensor/vacuum switch inside the air filter that cuts the vacuum to the door once the air temp inside the air cleaner housing reaches 100 degrees then the door opens allowing outside air through the snorkel again.

 

OK so I checked the choke and it is opening correctly.
Im still getting black smoke out of the tail pipe though.

I went ahead and turned the idle screw in a little to help it idle slightly faster so it wont keep dieing off.

Here is what I seem to have now.

It runs fine at idle ( after adjusting the idle speed )
It runs fine under slow load. ( both in and out of gear )

It does NOT run smoothly under heavy load. ( when I goose it while its in gear, its fine in neutral or park )

I am now thinking this may be a timing issue or a carb issue.

IDEAS?

 

Maybe its a diesel lol

 

Yeah well its definitely not a diesel, lol.

So I have a new theory on my issue.

My carb vent tube hose had gas (liquid) coming out of it.

1+1 in my mind says, black smoke + lack of power under load + gas coming out of vent tube = stuck float or needle valve?

I'm going to work on the truck tomorrow morning I'll post my findings.

 

OK news....

I checked the timing this morning and I appears to be close to 13ish maybe more like 14 degrees BTDC.

Now I AM getting a backfire through the carb under load.

Still wants to stumble, backfires, and bogs out if I floor it.

Should I retard the timing closer to the 10 degree mark on the timing?

Thanks.