You have to know what system you have . If you have Common Rail injection Cummins , that you should have in 05 , never crack a fuel supply lines at the injector; or any where past the high pressure pump; , fuel pressure there is high enough to penetrate the skin and KILL you.
The older systems (ISB with VP-44 pump in particular 98-03) often required bleeding air out of the injector tubes, the lower pressure involved makes them less dangerous,. But the Common rail engines the injectors are electronically fired and will clear air out of the system eventually.
If you are still having problems the lift pump may be failing, not providing the fuel flow required to purge the air out of the system.
Cycle the key on without cranking the engine , wait for the lift pump cycle to stop ( 20 -25 sec ) repeat 3 times. On the 4th key cycle bump the starter about 2seconds of engine cranking then repeat 3 key on cycles. Then attempt to start. No more than 30 seconds of cranking to avoid overheating the starter. If the engine fails to start, wait 10 mins for the starter to cool and the batteries to recover and repeat the whole process.
If in 3 repeats of this the engine still will not fire. The lift pump will need to be checked out, sometimes they will run ( you should be able to hear the pump if you're beside the engine during the 20 second run time ) but not pump any fuel .
BTW; Welcome to iRV2, sorry your having problems.
EDIT: Depending on how the fuel lines are routed , the primary filter may be between the tank and the lift pump, the lift pump may not be capable of sucking the air out of that filter housing. Drop and fill the primary filter. Once the lift pump has a prime , it should have no trouble filling the secondary filter and purging the air, using the key cycle method.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.