My 1985 vette starts up cold good and no smoke but after warm up it don't want to crank when it does it has black gray smoke for a min what's wrong

Check for vacuum leak .and check pcv

Could be vapor lock, but lost likely a timing issue. Perhaps a valve out of adjustment. Hard to tell without actually hearing and seeing. Does sound like a timing issue. Are there any codes in unit?

Your will need a road test with a professional scan tool
& record & look at data

IF ---you never do any Preventative Maintenance & few folks
do,anything at all,then problems are coming your way

Flashing MIL Lamp-- is a Class A-- Exhaust Converter Ruining
Cylinder Misfire

Runs Rough,Black Smoke --BUT--you keep using it & only
now, think maybe something is wrong !!

That car has lots wrong,that needs work,way too much to
write a book on it here, for you

Your Fuel Trim must be sky high

No fuel control & lots of misfire counts

The 14 years from 1997 to now, the converter is worn out,
but you have lots to do before replacing that

Starts good cold, because your in open loop & the fuel is
controlled by the PCM

Once it warms up & goes into closed loop,you have no
fuel control

replace your anarobic valve then do a diesel compression check of each cylinder

Hmmm...maybe piston ring failure, valve seal failure, rich air/fuel mixture or maybe a head gasket (however that is normally white smoke due to coolant burning instead of oil). If it's so dark that it's almost blue then I can tell you that somehow oil is getting into the cylinder and burning alongside the air and fuel. Your best case scenario is that the engine is running rich (Rich:Too much fuel, Lean:Too much air) and the smoke is a dark grey to black color. CAUSES OF SMOKE

Absolutely not, the automatic choke is defective. Replace that and it should be fine. It will need to be adjusted when cold to fully closed position. Check vacuum lines as vacum pulls the choke back when engine is started.

fuel injectors or glow plugs

If it finally starts after a lot of cranking, I'd have a look at the glow plugs. If they've not been changed since the truck was built, they've probably come to the end of their life.

Is it gray, bluish gray, or white? White smoke, during warm weather, indicates that you have a head gasket out and it's vaporizing water, it will look much like it does when you first start it on a cold day. Bluish gray indicates burning oil, which could be bad valve seating, severe engine wear on your piston rings and oil is blowing past them into the combustion chamber. Grey smoke is probably water as well, though it could be contaminated with oil, or the vehicle could be running too rich, getting too much gasoline. But typically this is more of a black smoke than gray.

hello. Thanks for choosing fixya! I would begin by getting this baby scanned. I agree with you that there are some carb. issues, such as gumming which could be cleared up with a couple of bottles of Seafoam, from your local auto parts store. Good luck with it. Regards, Joe