Fuel pump would be my guess, but make sure it's getting voltage as you crank the engine before you throw parts at it.

 

You've got to start with the simple things. Check for spark. Get a spark tester, pull a coil and check while cranking. If that's good, remove a connector from one of the injectors and hook it to a digital volt meter. You should see the injector voltage pulses as the engine is cranked.

 

Hello, I recently purchased a 2008 Ford F-150 5.4 3 valve. The guy I got it from had already cut the cats off it prior to me buying it. It cranks over find and it has started a few times. I changed the fuel pump, the fuel pump driver, filter and all fuses are good. I'm not getting any spark. My anti theft light blinks and when I turn it over it goes out while cranking. I haven't replaced the cats yet so the exhaust is pretty much disconnected from the intake. I unplugged the wires from the sensor and I probed them while cranking and no power there. I need help bad... Thank you.