My car is not starting?

My car is not starting. The first time I tried was on yesterday morning, around 9 am--it was very cold (about 20 degrees Fahrenheit), so I chalked it up to a cold morning. Today is warmer, (about 45+ with sun) and it still will not start. When I try the ignition, it will only make sounds like the engine is trying to catch, and the faster I pump gas into it, the faster the sounds come, but there is no regular "running engine sound". When I let go of the keys, there is only silence.