sputtering

if i let my truck sit without idling for over 3 days, then when i start it it sputters and dies in about 5-10 seconds. temperature does not matter, it happened in february in wyoming and it happened in florida in july.
if truck sits less than 3 days there is almost no sputtering.
if truck sits for a day or so it starts perfectly.
anyway, no matter what the case is if i pass that initial phase it runs and idles perfectly. the only problem is first 5-10 seconds (after truck sat over 3 days) when if i don't step on fuel pedal it is gonna die and sometimes even that (stepping on fuel pedal) does not help.
fuel filter is clean, i drain fuel separator each nite, i add additives in fuel so there is no moisture in fuel. cummins, freighliner, century class, 2001, 843000 miles. there is no fuel leak. could it be sucking air? has to do with time , temperature has nothing to do with it.