I would have a fuel pressure gauge handy as well. You should see 4-7 psi min. you should NO air.My thinking at the moment is this.
1. Failing fuel pump. It does work some tho cause I put my finger over the suction side and pumped the lever a few times and got some suction. Not sure of why I can`t suck fuel out of a pail even with the damned electric pump. That`s just weird
Barring some act of god, I's say the LP is no good. If it won't suck even from a pail unless the line you have from the pump to the pail is bad.
2. Leaking fuel filter. When I think about it, the problem got a lot worse after replacing the FF a few weeks ago. Also it took a LONG time to get the truck going after the filter change. Then I had a no start the next day. I've felt fuel at the bottom seam but there's been fuel everywhere in the last few days.
3. Various pin holes in the supply line. I found one hole that was under a zip tie that was holding a return line to a supply line. Also fond some a clean area of fuel line along the frame rail. Nothings clean on this truck. Don`t know if there was a leak or not but I cut the line as close to the tank as I could get. Lots of old dirt where I cut so no fuel leaking in that area or above.
Common spot for these unseen to the naked eye is on the fuel line pickup right where it bends to the tank.
4. Possible problem with the pickup tube, that one I`m not so sure about though since when it`s running it runs with very little air then without warning there`s huge air and stall then no start.
5. My disintegrated cab mounts make the cab crush part of the pick up tube soft line. Don`t know if this is possible but the no starts have been mostly when parked with the pass side up on a snowbank. Surging has been most common when making turns, both conditions that make the cab move around.
Sounds like you know where to look.
Hope that helps.