1998 Sierra cranks then shuts down
 

My sierra has had the same problem for about 6 months. It will run fine for a month or more, then it will crank and start, then immediately shut down. It recently did it and my check engine light came on, i checked the coed and its an EVAP leak detected code. Dont know if thats causing my problem but sure could use some suggestions!!

What code is it?