Archived Truck won't start, possibly temperature related

[Bernie]

History
-2003 truck, HO, auto, stock except for air intake and filter
-About 196k miles
-I have had it about 110k of those miles. No major repairs (except wear parts in the drive line and suspension)
-I rarely plug it in, as it rarely get super cold (below zero)
-Recently it did drop to about 14 below for a couple of nights. Forgot the first night, and it wouldn't start. Remember the second night, and no problems.

-Wed to Thursday, truck was at the airport in the teens. Started no problem.
-Filled the tank, drove home. It was about twenty over night, so I didn't plug it in.
-No problem with the drive home, and it was a major station, so I doubt the fuel was old or bad.
-Friday, truck would not start. Again, about 20 degrees. Plugged it in, and a few hours later it started.
-I left it plugged in, but apparently the GFI tripped at some point. It won't start again.
-For all of these no starts, it cranks fine. Not a voltage problem.

Analysis
-I have verified plenty of oil, good voltage, grid heater is working, and block heater is working (unless GFI trips)

Question
-Why all of the sudden has my truck developed a dislake of barely cold weather. It used to start fine down to zero, and only needed to be plugged in when it was sub zero. Why, with 20 degree nights and 30 degree days, has it become a problem?
-Why, when it dropped to zero during the time it was at the airport, did it start then and not now?

 

[JFought]

if you have weak batteries the starter wont turn motor over fast enough, to get a min fuel rail pressure to fire the injectors.

(one of many different things possible)

 

[Bernie]

I have had the starter turn slower (on colder nights that it wasn't plugged in) and still start, so I doubt that is the case. I have new batteries to go in anyway (current ones are original to the truck in 2003!), so I will be doing that this week anyway.

 

[p-Bar]

The 03 has the cannister mounted fuel pump has that ever been replaced with the intake? With that many miles I assume it's been replaced

 

[Bernie]

Update: After two hours plugged in, it starts!

No, I have not replaced the lift pump. I have a spare just in case, but to date in the last 110k miles I have not needed it.

I guess at this point, I need to focus on which components will work properly when warm, but will not work when cold. Suggestions?

 

[Missouri Mule]

Bernie, take a fuel pressure test. I have read threads about 12 valves doing this and as I recall it turned out to be the lift pump.

 

[Hoefler]

Worn injectors will also cause a hard start no start condition as well. They won't atomize the fuel fine enough to fire off when it gets very cold.