what would cause my 91 first gen 4.3 vortec to start hard in summer and start great in the winter. It does start though in the winter when i go out to start it it starts right up with no hesitation but in the summer it is just the opposite

 

Possible EVAP system problem. Gas expands in the tank in the summer creating more pressure in the tank. could be a venting problem or bad gas cap. Don't really know of any other type of issue that would cause that.