6.6 help

I'm working on a 05 c4500. It has less than 60k miles on it. Unfortunately it had to have the fuel line that runs from the tank replaced due to having a hole. It also formed a draw on the batteries that led to the alternator being bad. The batteries are less than 6 months old and have been tested. It currently won't start on its own. All filters have been changed. It starts with a spray of silicone only. Even if it's been running a while. No codes at all nor lights. I added a little pressure to the tank and still no luck. I push and push the primer while its running and it never gets solid. Could anyone point me in a good direction? Thanks