If I let my truck sit for a couple of days and then start it. It fires right up then dies after runing for about 3 sec Then it takes a good bit of cranking to get it started again. It acts like its out of fuel.
I cant figure it out

 

Air leak in the fuel line check your fuel filter also.

 

Mine did that it turns out i was leaking fuel at the shrader valve. You might want to check that and all of your lines.