our lincoln navigator kicks over just for a few seconds with a starter fluid sprayed in air in take.Do you know why it won't continue running?

Yeah, don't do that starter fluid stuff, it won't run like that anyway. However, there is a theft light that should not be flashing in or on the dash, if it is while cranking, it will have to be diagnosed further at a ford dealership, also if you don't see the light flashing listen for the fuel pump by just turning the key on and not cranking the engine over, there should be a fairly quite whirring noise for a couple seconds coming from the fuel tank, if not it will need a fuel pressure test, to verify correct fuel pressure. Depending on year there will also be an "inertia switch" which may have been tripped if the switch tripped its in the pass kick panel by your feet. Bottom line, Ford has the correct equipment to solve your issue, not the aftermarket.