You might need to purchase a bigger battery with more cold cranking amps. Below zero weather will probably require a battery with 800 or more cold cranking amps.
There are several reasons why a Crown Victoria will not start. One reason could be a dead battery. Another reason is that the spark plugs and plug wires may need to be changed.
Dead battery, jammed starter rotor arm - it it's manual, put it in gear and then rock the car back and forth to un-stick the rotor arm. If it's the battery, main lights will be dim or not work.
I had the same problem in an old Chevrolet, and it turned out to be a short in the battery. Check it out.
If the alternator is bad the car will still start. You just need a fully charged battery. Once running then you can check the charge rate from the battery with a volt meter.
It would be helpful if you can explain the " won't start " Does the engine turn? If it turns does not fire? Was it running before?
if it tries to start with out a keu when you hook up the jumper cables, you have a bad starter solenoid.
Battery could be dead. Check that with a volt meter.
try adjusting the ignition timing .
check and replace rotor in ingnition distrib.and check spark modulator
Does your underhood light come on ? or if the key is in the ignition with the drivers door open , do you hear the door chime ? If not , it sounds like a bad battery cable connection or a dead battery
Same thing happend to my truck. Change your distributor cap and rotor. Sparkplugs wont hurt, they're cheap. But its your cap and rotor.
Battery is most likely dead.