Posted before but wanted to do a concise summary so here's another post. This is the most maddening problem I have faced in 20+ years of brick ownership and I'm hoping somebody will have some new ideas for me. Symptom is intermittent crank but no fire. I walk away and come back in 30 minutes it usually starts right up. If I unplug AMM it usually will begrudingly start in limp mode and get me home. Once there I replug AMM, clear code and then the rest of that day, the next day and maybe up to a week it behaves as if nothing is wrong. I've cycled thru the 2 good AMM's on the shelf, driving each one for several weeks and it acts the exact same with each one so I don't think it is AMM. I also had a hunch aboout the pre-pump so that is brand new (and the sock and hose) but that was not it either. So during the no start period:
1.) both relays in FPRelay are energized and closed
2.) 12vdc at fuse 4 during cranking
3.) 12vdc at both fuel pumps
4.) both pumps are operating or at least sound to be - jumped fuse 4 to 6 just to make sure with no luck
5.) noid light shows impulses being sent to injector 1 (didn't try 2-4 though)
6.)spark gauge on plug 1 in the dash (homemade lite gauge) shows spark during the no start period
7.) can feel squish of fuel in the return hose on the back of the FPReg with 4 and 6 jumped and also if I push the valve on the rail there is a puff of fuel/air coming out
8.) plugs get wet

Buggered up the threads on my fuel pressure gauge so can not measure the actual pressure at the rail but the "signs" are that it is good. So frustrating - all the ingredients are there but no start. I have not considered timing, compression air etc because I can't see these being so intermittent. Any ideas out there? My only idea is that maybe the ECU is altering the "mix" of the ingredients and changing the timing on me but this seems like a long shot due to the intermittent nature. Hoping somebody's got some ideas...
Robb McC