Is yours equipped with an 'inertia' switch? The underhood labels should say ,if so. Location may be in trunk or under pass kick panel. Sharp smack with small rubber mallet , to make sure it's completely 'tripped' , then push in firmly till you hear a very deliberate click and it stays in .(that's all from memory from an old taurus I had and those wonderful times it wouldn't start) If I'm on the wrong track , hopefully someone else will chime in!