I have about 3K miles on a freshly rebuilt engine and recently have started having hot start issues. Starts well in the morning and after the engine is warm, I will need to crank and crank to get started.

During the cranking, I will almost get a start and have some pretty black smoke bellow out from under the hood in the area of the intake manifold...usually after this happens, it will start after a couple of cranks.

I've replaced both the control pressure regulator and the thermal temp sensor with parts from the junkyard and still have the same issue.

any ideas?