2002 Duramax won't fire
 

02 duramax cranks but won't fire.
I left it sit overnight and fired right up in the a.m.
haven't had the problem again but have been told everything from fuel pump to injectors to key/computer not communicating...
NOTE- never had this issue before-has been a good running truck-use it to tow RV.
It smokes when sits and idles-has been for a while just haven't got $$ all together to get injectors replaced.
leaving on trip in a week-would like to solve before then

smoking while idling is usually an injector situation. does it have trouble starting when warm but starts when it cools down? any codes?