Not the GPR or GLOW PLUGS

[stock]

I have been noticing harder starts lately first thing in the morning. I have checked the GPR and it;s good. I have checked the glow plugs and there within spec. The only thing I have not checked is the fuel heater. Do you think that at -5c (27f) this could be the problem.. I checked the voltage going into the fuel heater and it looks good. How do you check the element though?? Do you take off the fuel filter and check from the in side?? Any one know??

[ridiculously_necessary]

doutn the fuel heater is the issue. how fast does the starter crank?

[stock]

The starter seems to turn over fine. I read that if both batteries are not fully funcional that you may not be getting good glow plug heat. Once the truck has it's intial start in the morning it starts fine all day long, even if it goes to work at 0900 and gets started at 5:00pm it still starts good, it's onlt the morning that i have problems.