Thanks for everyone's input. Can't get out to the truck tonight but will tomorrow.
I am also thinking lack of fuel pressure to the rail.
As for the fan, I've seen posts where people say it won;t start, but it seems there's always been a seperate underlying issue. The truck has started and hasn;t started so not sure if the fan would make a difference, but if it doesn't start in the am, I'll try unplugging the fan. I believe there's a connection under rad cradle. If someone could point me in the right direction for location, that would help.
As for gelling, fuel is entering the filter housing and the truck has started without ether in -20 C so I can't see gelling being a problem. And if it only started with ether last night (-15 C), again, if the fuel was gelled, how would it get through the system for the truck to run? Just thinking out loud.
My understanding is the CP3 is a 2 stage pump...first stage boost to approx 200 PSI and second to whatever the ECM is telling the FCA to do based on readings from the FPS (fuel pressure sensor) on the rail. (I've yet to look at the link provided as just got in, but will this eve. Thank you for the link!)
I will get the truck running and then unplug the FCA as suggested and see how it runs. And yes, starts with ether and then runs, so eventually the rail is getting the minimum 5,000 PSI require. If I have that right...I hear 4,000 and I hear 5,000 and I believe that's output from the CP3, but it does seem during cranking that it's not getting fuel. Does not want to fire at all. And when it does start, it's within 3-5 seconds, which I think is acceptable given the temps.
As for cycling grid heater, that doesn't seem to be the problem. Sometimes it starts; sometimes not. I do know they are working properly though as they both are receiving 12V when cycling, both have continuity and the intake tube gets quite warm.
Batteries are 2 months old. Keeping them charged during the night and the engine turns over at over 150 rpm. No issues with cranking over.
Will update tomorrow and thank you so much for the suggestions!