If you can get a fuel pressure gauge from a parts store like autozone (they will loan you one for free with a refundable deposit) and hook it to the pressure test port on the fuel rail and observe the pressure when trying to start it,,you should have close to 35 psi, not much lower, or it won't start. If it is lower, then unplug the vacuum hose on the fuel pressure regulator on the fuel rail and see if it goes up, if not, and you can hear the pump, then the pump is not delivering enough pressure because it's not turning fast enough.
Couple of tests you can do as well. If you have a can of starting fluid or spray carb cleaner, you can spray some into the air intake to the engine, and if it runs on that, then you know for sure it's a fuel issue.
One more thing you can try is to take a rubber mallet and smack the bottom of the gas tank while someone is trying to start it, and sometimes it will jar the pump and spin faster and start, BUT, you still should still replace the pump.
Try to get a pump from the dealer if you can, they are more expensive, but most of the ones we see that come on the aftermarket tend to fail way too soon.
Try this out and If you have further questions feel free to reply, if not please click on accept so i receive credit for working with you today. You can always reply back after you accept for any follow up questions, and there is no extra charge :-)