05 Duramax
 

i have a 05 duramax if i park up hill i loose my prime the engine will run for a few seconds then it dies. and i have to prime it up and it's ok. if i park it on level ground or with the front of the truck pointing down it will crank fine any ideas ? some one told me that it was my fuel filter im using a fram right now, fixing to use napa's supposed to be like a wix need help thanks