So two years ago I fixed a hot start problem by changing the nipple cup seals and all the injector top seals.
They were pretty beat, but the big failure was the #6 injector seal. I also took out the HPOP and changed the STC o-ring at the same time (the STC was upgraded to the good kind before I bought the truck)
I figured I had it taken right care of because it has started and ran great for about 40k miles since then, with a good deal of idle time (service truck).
So a few weeks ago I developed a slow cold start issue, followed shortly by a slow hot start, and soon after that a slow cold start only and no hot start. Having been down this road before I knew what was likely broken, ICP pressure slow to build on cranking, but in spec when running.
I took a gamble on it and took off the drivers side oil rail today (hoping to be able to use it tomorrow for work) and found the #6 seal in rough shape, and the #4 seal a little beat up, they all seemed a bit stiff, even though I used Bosch seals the first time.
The nipple cups all appear to be in great shape still (viton gaskets) practically no movment on them, and no sign of oil spray or broken seals.
So what is causing the injector seals to get torn up in under 50k miles? Worn nipple cup? Worn injector cup or snap ring?
Anyone dealt with this as a chronic problem? It sprung up rather suddenly from delayed starts to no starts, but the hot weather keeping the oil warm probably doesn't help.
I will note that the first time I found no real problems on the passenger side other than stiff seals, so I'm going to just do this side for now and see what develops, hopefully the issue is resolved, at least for another 2 years.