I've been trying for a few days to figure out what's causing this. I've replaced:

Fuel Filter
Fuel Pump
Fuel Pump Relay

I can get it to start but 30 seconds in (sometimes not even that long) the engine cuts out. No sputterting or weird noises. It just dies. I haven't noticed any vacuum leaks. I'm really banging my head on a brick wall on this one. Help!