2000 F150 with a 5.4, 4wd, and automatic.

so far weve replaced the starter (was under warranty) firewall relay (had 200k miles on it) cleaned the battery cables, and checked the battery voltage (was a little on the weak side, but was ok. something like 10.9v cranking)

in the morning when the truck is cold, it will start without fail. but after running around town for awhile and making 2-3-4 stops, it may or may not start. theres a "click" but thats it.

tried starting in park or neutral, and its the same thing. just a click.
tried rolling the truck back and forth a couple feet in neutral, and then tried starting in P/N, and again, just a click.

sometime when its starting youll hear the click, but then as you hold the key, it will start cranking half second later. or it will click and then instantly start cranking.

the CEL is on and has 3 error codes last time i checked it. cylinder misfire on plug 1 and 7 (2 cracked heads.... oh boy) and bank 1 too lean.


at this point im running out of ideas as to what would keep it from cranking.

 

Get the battery load tested. Replace the 2 misfiring plugs (and cops if just the plugs doesn't fix it) and look for a vacuum leak or exhaust leak on the passenger side before the O2 sensor.