Diesel wont start

Try draining and blowing out the fuel lines and cleaning the injector inlets.

Use a multimeter to track down where and why the lift pump isn't getting the proper voltage. Maybe a loose connection or wire. Or a corroded connection or relay.

Contacted my diesel expert, and he agrees, we need a whole lot more information. What temperatures? Is it plugged in? Have the injectors been replaced?

My first though was there's a problem with the intake air heater but my buddy says that is very unlikely. He has rebuilt a lot of smashed trucks. All Dodges as that's all he likes, and mostly diesels. He said the two most likely things to suspect are the injectors and the injector pump. The injectors can get a little spec of dirt stuck inside. Don't know if that's accurate but apparently he has had good luck after replacing them. He didn't say what the problem is with the pumps. I don't know why temperature would have such a big affect unless there just isn't enough fuel getting in to fire properly.

First, I would have the air heaters checked to be sure they are working.

Is the check engine light on?

Roy