Been fighting this for a while now. I'm doing a tune for a friend. Its an 03 Silverado rcsb 5.3, it has headers, ss3600 stall and an Isky 212/212 cam 112 lsa. Now I've tuned MULTIPLE cammed LS engines but never had this issue before. Basically when you try to start it up it just cranks and cranks but doesn't fire, then just let off and try again and most of the time it'll fire, it doesn't do it every time though. Once it fires up it runs fine. We've tried cycling the key before starting thinking mabe it was bleeding fuel pressure off but its not. I sure wouldn't think with a cam that small I'd need to do any crank/start adjustments in the tune... I'm not around my pc right now so I cant upload my tune, but I will as soon as I get home tonight. Any ideas?