Where I live right now we have very cold January's. Today it hit -40 Celsius. I have a 1995 Buick Le Sabre 3800 3.8L V6. I had the car plugged in for a hour today and it wouldn't start. I also tried to boost it as well with another battery and no go. I last tried a battery charger for a hour and nothing. What happens is the car will crank very slowly and then hiccup and cough and almost start then the ignition clicks. I was thinking it could be the Fuel Pressure Regulator?
This is probably electrical. First check the coolant to make sure it is not freezing, which causes catastrophic engine failure & check the coolant level. If coolant has entered the combustion chamber the engine may not turn over. Check the engine oil to see if it is inundated with water/etc. If the coolant and oil are okay the battery, battery cables and/or starter need testing. Voltage drop testing with a multimeter is recommended. If you cannot perform electrical testing you can remove the starter and battery and have them bench tested at your local parts store. You can visually inspect the battery cables and grounds. Clean up any corrosion and reestablish a good connection, including the engine ground.
Mechanical damage to the engine is also possible along with a few other remote items.