Won't start - before that, hesitation while driving

Engine cranks strongly but won't start (doesn't partially "catch" at all). Leading up to this, there was intermittent very brief engine hesitation (like I've experienced when almost out of gas), but car had full tank. One day, it simply died while driving, & wouldn't start again. I suspected fuel starvation, but not certain.

Replaced fuel filter & turned ignition key on (not as far as start position). Fuel pump whirred, like normal. Turned key off, disconnected output line of fuel filter & fuel pressure seemed strong (gas squirted out, not dripped out).

Engine is direct injection, but there's no pressure valve on either fuel rail (nor elsewhere in engine compartment that I can see). So, can't test actual fuel pressure when key in on position, nor tell if there's an air lock.

What are next most likely trouble spots to check or test? Am I safe to assume that fuel pump relay & fuel pump are both working properly if pump whirrs, like it sounds normally? Or, am I barking up the wrong tree entirely?