Ford 7.3L Power Stroke (1999-2003) :: Crank No Start Sometimes - Stutter / Stalls And Slow Acceleration

I have 2001 F250 7.3L 261k miles.

Over the last few months, I have noticed that my truck is taking longer & longer to start after sitting for a long time (i.e. every morning, after work, etc.) When the problem first started (3-4 months ago) it would crank for 2 seconds & nothing so I would turn it off, let the "wait to start" light go off again (depending on outside temp 10-20 seconds) & then it would crank & usually fire right over like it was new. That seemed to happen only in the morning when it was 70 degrees or colder outside but no problem after work when it was 80+ degrees.

As the weather has gotten colder, it has gotten progressively worse. A couple of weeks ago, it was in the 40s in the morning & it took a solid 8 or 9 minutes of cranking for a few seconds, then trying again before it started. Once it started it did "chuga chug" a couple of times before it smoothed out. Last week when it was 16 degrees in the morning, it wouldn't start at all. I tried for a solid 15 minutes before I gave up.

I will say that as it has gotten worse over the last couple of months, I have noticed that it's cranking w/o firing but I will hear it fire once or twice per crank before it will fire up & run. Once it starts, it runs like a champ. No studders, stalls, slow acceleration, etc. Pulls like it always has. The weirdest part about it is that once it starts & runs for 30-60 seconds, I can shut it off & it'll fire right up every time. If I get it up to full operating temperature, I can go back & start it right up 2 or 3 hours later w/o a problem.

I did notice my oil cooler is leaking pretty badly (that will be fixed this weekend) & my valley has fluid in it but it's hard to tell if it's diesel, oil or a combination of the two because my truck is setup to run on WMO (waste motor oil). I have dual tanks so the OEM tank is diesel & the auxillary tank is WMO. I have 2 mechanical fuel pressure gauges on my fuel bowl, 1 pre & 1 post fuel filter as well as an aftermarket Walbro fuel pump. The fuel pressure when running on WMO has always bounced a little bit between (65-75 psi) but the fuel pressure on diesel has always held solid at 75 psi until recently when I have noticed that it flutters a very small amount between 73-75 psi.

I have verified that the GP Relay works & was leaning towards a glow plug problem but considering it was having troubles at 70 degrees ambient temperature, I'm hesitant to think that's the true problem. I think that might just be adding to the problem. I live in the south so my truck doesn't have a block heater but I'm going to add one this weekend when I replace the oil cooler gaskets & o-rings.

I'm also going to pick up a new Android tablet today (replace my broken one) so I can use the Torque Pro app to monitor ICP, HPOP & InjPW. Finally, I had a DP Tuner chip on it & to remove that as the possible cause, I removed it & the same symptoms continued.