03 cummins won't start
 

I'm havin some problems with my 03 and I just got it but when it gets really cold like -10 then I don't think I'm building fuel pressure because I've got a fass 150 lift pump on it but it won't fire when I crank it so I cracked the injector line to see if the rail had pressure and at first it didn't at all and then all of a sudden it built it up and the truck fired up. So I don't know if it is the cp3 or the regulator on the cp3 or the fuel rail pressure. Because its always been a little slower to start. And I've also got a crazy Larry bully dog chip on it and it doesn't seem like it's fueling as much as it should because there is no smoke and I don't want smoke but I know it should with that hot chip on it, what do you guys think? I pretty sure it's not the lift pump because its new and I've had to bleed it a couple times and it has great pressure. Help!

OK, start over.
Will the truck start at all warm or cold? Plugged in?
When you put the FASS on did you delete the original fuel filter canister with the fuel heater? If so then your fuel could be gelling prior to the CP3 when its -10 degrees. The canister has a fuel heater that activates with your intake heater grid and while you "wait to start" in colder weather it heats the fuel from the canister to the CP3.
If you live in shuch a cold climate you should consider running a coolant line to your FASS unit and you can also run a glow plug in one of the ports at the fuel pump that will cycle with your grid heater relay thus warming the fuel at the FASS, but that wont do much good if the FASS is mounted on the frame rail.