What oil? Synthetic helps alot in the cold. I can leave him unplugged it will start just fine if its 0 out. When I had reg oil in it even at like 30 degrees it would crank over slow and then lope and chug. Synthetic is so much nicer. When was your last oil change

 

i would change fuel filter, if you have any moisture in system fuel will gel, also try some fuel treatment and i bet your prob goes away. and im not a powerstroke guy but some trucks have 2 filters.

 

The only filter is in the bowl. Never hurts to change it, and a little power service in the fuel helps

 

I was just going by the idiot light and when it would go off i would try to start.It would start rough. I learned the glow plugs cycle for 2 minutes,so turn the key on and wait 2 minutes then try to start. This has worked so much better.The light is just a reminder and goes off while the plugs are still trying to warm cylinder.In very very cold I will cycle the key twice before even trying to start.This and syntetic oil have made a huge difference in cold weather starts.

 

i had similar problem with mine. i changed the glow plug realy and now it fires right up. plugged in or not

 

like kyle said it could be something with the oil, if the eng doesnt sense oil press. it will shut down

 

Just to be clear...

The 7.3 has no idea what the low pressure oil pressure is... There is a pressure sensor in the HPO Res that is a on off switch... Unplug it and the truck will still run fine.

The truck will die if there is no High Pressure Oil Pressure, but the OP issue is nothing more then a cold diesel with one or more Glow Plug related issues...