Any great cummins diesel guys on here?

hi guys
i have a problem with my 2004.5 325HP dodge ram
Problem is when it is below 50 degrees outside this truck cranks and cranks sometimes it starts but most times it wont,
i have a DRB3 scanner and have checked the following
1. no codes
2. fuel pressure from lift pump 23psi to 30psi while cranking
3.
CP3 pump pressure
1200 psi while cranking
6500 to 6700 while running

4. intake heater is working
5 block heater working
6. no blow by, no smoke when running or starting,no fuel in oil
7 fuel filter changed 800 miles ago and had same problem before changing filter

The truck runs great after getting it started, can drive 5 miles and shut it off for 6 hours it will start with in 3-5 seconds of cranking over
SO this issue is after it sits for 8-12 hours and when its 50 degrees or colder outside,
parts replaced so far are CP3 PUMP,CROSSOVER TUBES,FILTER.
drove it 150 one way A FEW WEEKS AGO AND THE INTAKE HEATER LIGHT CAME ON IN DASH no CHECK ENGINE LITE ON
Code was P 1222 undefined code but youtube says its Excessive fuel return ??
im at a loss here some are saying bad injectors? Really dont want to guess and throw $2800 worth of injectors in this thing
if i plug truck in and batteries are charged it will start after a 5 to 15 seconds of cranking.

any ideas???
thanks for any help