Wrong. No oxygen is left so it can’t burn. It exits the exhaust as unburnt fuel exactly as you stated in your original comment.

Extra fuel in a diesel cycle is used as coolant just like in any of the gas cycles. Gas is see through when it vaporizes, diesel isn’t. A turboed gas engine rolls coal too but it only smells bad if it lacks emissions systems.

I hate rolling coal but running rich is used to protect an engine under high power output conditions. Mostly in forced induction setups. Extra fuel lowers cylinder and exhaust temperatures because it vaporizes without combusting, pulling heat out of the air fuel mixture during the compression stroke. Leaning out too much is death to an engine.