I have a 2005 Mercury Sable - it's is hard to start; I to check turning the key on and off and eventually it starts. The lights, radio all come on when I try to start it. I have a new battery
You mentioned that you turn the key on and off and that is essentially priming the fuel system. Have the fuel pressure tested, might be a weak fuel pump or faulty fuel pressure regulator. When was the last time you replaced the fuel filter. I change mine every 30-50K.
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