need help bad truck not starting

[Mike sr]

I have a 03 expedition that won't start has no codes was told starter alternator and battery was good replaced pcm and interior Fuze box still won't start but will start n run once jumped by the starter please help love this truck very sentimental to me motor n Trans runs great

 

[Trainmaster]

Solenoid or battery clamps or cables. Check for fusable links. Then troubleshoot ignition switch and any relays associated with the starting switch.

 

[Vincent Vega]

When I had a similar problem, it ended up being a corroded cable between the battery and the starter. Back then, I never cleaned my battery, so corrosion migrated from the battery connection along that wire until eventually it stopped conducting altogether (I clean my battery at every oil change now). Also, the Exp has several ground wires which sometimes get corroded or damaged, so check those. Other than that, do what @Trainmaster suggested, and/or re-verify the alternator is ok.

 

[Motorcity muscle]

"Once jumped by the starter" will assume means when 12 volts is put to the starter directly. If all good when running then, has to be positive battery cable from battery to the starter, as suggested above. Check for crank signal from key switch to starter solonoid.