I have a 1989 dodge d350 dually with a 4 spd manual and a v8 360 and when I first start the truck it fires right up with no problem, even if it 90 degrees outside but if I run it and it gets warm and shut it down and go to restart it again it takes longer to start and pushing on the gas help it start quicker too. What would be causing this?

 

Check you fuel pressure first, If that checks out look at the idle motor. It may not be pushing the throttle enough when it's hot.