Heater core change - truck cranks but wont start
 

I have a 1999 F150 5.4L XLT and after a long but uneventful heater core swap my truck wont start. it cranks but wont run.
Things I've checked:
fuel pump fuse - good
fuel pump relay - clicking
inertia cut off switch - down or up no difference in fuel pressure
i put a fuel pressure gauge on the fuel rail and fuel doesn't bleed out when i press the release button. Ive tried this with the inertia switch in both positions. i have tried it while cranking and just a few seconds after turning the key to the on position. There is no pressure reading at any time. the fuel pump supposedly was changed in 2015 when i had to have the tank re-lined/epoxy coated due to corrosion. the truck sat for 4 years with a blown engine but i had it and the tank rebuilt at the same time. i didnt do the work so im not sure if the pump was replaced. I am looking for any other areas of the truck that could stop the flow of fuel or a way to know for sure that the pump just went out. Everything was working before the heater core swap. I have been all over that dash multiple times looking for plugs i may have missed but found nothing disconnected in the dash or kick panels. for reference the battery was completely disconnected the entire time the heater core was being replaced.

Is there a place inside the cab where i can find the fuel pump wire on its way back to the pump (not interrupted by any circuit)? just making sure i didn't pinch or cut a wire when the dash was being manipulated for the heater core repair.

Apart from checking the pump itself I am out of ideas.

Thanks for any help.

Check the fuel filter?

Did you actually check at the inertia switch with a voltmeter to see if there is battery power getting passed back to the pump during the initial priming cycle? Basic troubleshooting step....

After my post i thought about how i saw no difference between the inertial switch being up or down and decided to extract it and do a visual on it and noticed that the plug was disconnected and tucked behind a thick wire cluster making it look tight and factory. I plugged it back on and the engine fires right up. sorry for the false alarm but hopefully this will help others.

oh and one side note for anyone in the future, the blower motor plug exactly fits this blue unused plug (easily within reach) in the kick panel. i usually expect the plugs to be different shapes so this cant happen...but now i know.

Good news. You learn something new every day. :)

You might want to check your shifter cable, the cable outer housing can crack easily when bent, look where it connects to the shifter lever on the steering column and follow it down to find the break.

If you read the OP's posts fully, you'd see he already solved it.