Ran great until we went arctic. It's a lot colder than we normally are around here. I think the glow plugs are working, I've cycled them a few times and it didn't work. Last time it was cold for us that worked to get it to turn over.
It's like it just can't turn over all the way, it kind of strains and suffers but just can't start. Now that you mention it I'm kind of thinking battery. Volts are reading between 6-8 after I cycle it and try and turn it over a few times. Timing was just done and is good. Finally.
I have small fuel pump after my sedimenter that I can hear running.
I’m guessing it is a combo of gelled fuel and a weak battery. Can you get the truck into a warmed garage overnight? If so a space heater under the block for a few hours would certainly help a lot.
Here is how to test your glow plugs.
Have you had a few cold/warm weather cycles with snowfall? I had a similar “strained crank” issue with my tdi a few winters ago. While I searched for answers I tented the rear and put a camp stove under the diesel tank to deal with possible gelling.
I turned the engine over about an hour later - it stained, then launched a cylinder of black ice out of the stock tail pipe like a mortar round. The heat must have melted it just enough... It may be worth checking your tailpipe is clear.