Car does not start when temp below freezing
 

With the recent freezing weather in NY my 1991 LS 400 does not start. At about 35%+ it does. I switched Fuel pump relay back and forth and they both start when its "warmer" I used gas treatment, changed dirty air filter, even cleaned relay port and relay with DEOXITD5 spray. Nothing has changed. Is it my fuel pump that's bad OR freezing up?
Otherwise car runs like a baby.