2003 infiniti has gas but acts like it doesn't & won't start

So it cranks over, but won't start? Probably either a gas or spark (ignition) problem. Listen for the fuel pump to turn on for about 2 seconds with key in on, not start. If you hear nothing, you need to check fuel pressure with a fuel pressure gauge-AutoZone loans this gauge for free. Just hook it up, turn key to on, and read the fuel pressure. Multiport injection engines need high pressure- about 40 or 50 PSI. Check the specs for your Infiniti.
If you have fuel pressure, check for spark at a spark plug wire.