Re: 99 F150 fuel pump suddenly quit.
two more things (still waiting to find a wiring diagram!!!!!)
the "theft" lamp in cluster lights up sometimes when cranking. (can't remember if that is normal or indicates the source of my issue with lack of power to fuel pump possibly related to anti-theft stuff) I just read up on PATS and that's normal...
Number 20 fuse (5A) in under-dash fuse panel has no power. owners guide states it is for audio, GEM and PCM modules. however, the radio/tape unit works without that fuse having power. w/o diagram I need to know where it gets power.
also, I swapped diodes in the under-hood fuse/relay panel, between the PCM and A/C clutch circuits. still no power to fuel pump.
If this isn't the best forum to be posting these technical questions, will someone PLEASE let me know where I can get in-depth info into the fuel pump system THEORY OF OPERATION as I'm still flying prettty blind.
oh, and I borrowed a scan tool. no fault codes are stored.
Looks like I hadn't mentioned THE ENGINE RUNS IF I SPRAY B12 INTO THE INTAKE, SO NO ISSUES WITH IGNITION.