I am wondering if on a 2001 ford fl50 has
had a fuel filter change and won't fully start
but will start if you use starting fluid in the
carbarator what else can be wrong and will
the truck stay running if I start it that way
You say it has had a fuel filter change? Can you hear the fuel pump working as you turn the key to the on position before engaging the starter? Isn't your ford fuel injected?
This sounds like the fuel pump may need replacing. Have the fuel pressure checked out, and no, you would be left high and dry somewhere if you turn it off, and eventually it won't start at all.