manicmechanic007

Double check #5 in the OP
Use jumper cables to verify a good ground source when testing voltage at the tank connector
Use the same cables to power up the pump and see what happens. See if it runs then or has fuel pressure

F150Torqued

Thank you for your thoughts on it @manicmechanic007, That aligns with my thinking AND @needsmoarturbo 's prior post as included in the documentation he provided - that the 75% Fuel Pump Duty Cycle reading --- "indicates the FPDM is reporting some circuit concern between FPDM and Pump". (( COULD be a Murphy's Law situation of my old 280,000 mile Fuel Pump failed - then I got a poor plug connection when I installed the new pump.)) My personal problem is the level of difficulty getting to that connection ( It's an age related thing that you young guys don't have the capacity to understand!!! LOL). I am going to go get my pocket storage o-scope on the fuel pump pins of the FPDM connector (with it plugged in) and cycle the ignition. ---- I don't even have a helper to do that while I'm under there!!!!! I will report back next steps to detail what I find.

F150Torqued

I would like to THANK all that chimed in and helped me keep my sanity and stay focused toward the solution. It __WAS__ "Murphy's Law" almost exactly as described in the previous post. It WAS a poor electrical connection in a harness plug --- but on the FPDM instead of the Fuel Pump on top of the tank. The 'take away' from this, 'confirms the prudence of my standard operating procedure. [ ALWAYS trust the OBDII Test Equipment data and balance that with the struggle required to "understand" what it is telling us -- with the urge to throw parts at a problem to lessen the time or physical repair effort.

RECAP: Original Symptom: Sudden development -- Cranked, but No Start.
The actual initial failure - Fuel Pump failed. OBDII (Torque Pro) produced only codes :Lean on both banks. Fuel Rail Pressure was Zero, Fuel Pump Duty Cycle reading 75%. This was always a VERY accurate report.

Original diagnosis was correct. OEM Fuel Pump failed (or possibly FPDM, - a known common issue) I succumbed to the above mentioned URGE - and replaced FPDM [[ but (MURPHY INTERVENED) and I failed to get good connection on FPDM connector ]] The symptom staying the same convinced me it was the Fuel Pump (which it WAS !!!!). But thanks to MURPHY, the symptom would have stayed the same anyway with the poor connection on the FPDM causing it to not activate the fuel pump anyway!

Of course, changing the fuel pump didn't change the symptom --- and MY reluctance to remove the spare tire again - or "heaven forbid" the fuel tank - obscured vision resulting in MY changing the Fuel Pump Relay on the Central Fues Box!!! Uhggg. Of course the symptom stayed the same because that NO the inertia switch had a damn thing to do with the problem..

Credits to @needsmoarturbo information "Fuel Pump Duty Cycle 75%" is a diagnostic indication of circuit concern between FPDM and Fuel Pump - confirmed by the documents provided by needsmoarturbo.

Credits to @manicmechanic007 for directing my attention back to #5 in the Original Post - which has proven to be location of the problem.

Relying on more detailed diagnostics / Further diagnostics - pin pricking harness wiring / the o-scope on "+" and "--" (Isolated from Truck ground) on the Fuel Pump output pins of FPDM, indicated NO voltage to fuel pump when Key is turned On. The PCM signal FMC (enable signal) was not making connection to the FPDM The aged/brittle plastic snap clip is broken. the fix was the wire ties shown in the photo.

Thanks again to everyone. Now to crawl back under the damn thing and get the spare tire winched back up there. It's an AGE thing !!!!!!

needsmoarturbo

Congrats on figuring it out. I have heard similar tales before of the connector gasket rolling up or otherwise causing the connector to not snap on tight.
hopefully solving these type of problems will at least help the mental acuity 👍

getterdun

Thanks guys. I really learned a lot from your posts. And I'm glad to hear it was solved and what the fix was.