99 f150 4x4 4.6l turn key on to "on" position, fuel pump comes on, and stays on, engine will turn over but will not start as long as that pump is running. sometimes the pump will turn on and off intermittantly (you can also hear relays clicking on and off), and you can get it to start if the pump stops. i have replaced fuel pump, filter, pressure regulator, relays in power dist. box, visually checked wiring under power dist. box, checked fuses, checked wiring to tank/pump visually inspected vac. lines. The ford dealer checked fuel pressure and said that it was fine, but it was above freezing and all of my problems are when its below 0 deg. truck runs fine when it's warm. i'm ready to jump it off a cliff (if it would start i probably would.) any help would be greatly appreciated.