1994 S10 4.3 CPI Cranks But Won't Start — 0 Fuel Pressure After New Fuel Pump

(1994 S10 4.3L V6 CPI Pickup)

I'm pretty sure this is a fuel-related issue. The truck started with a rough idle that would surge and almost stall. Over time it got worse and would die if it idled too long at stop signs or red lights. Eventually, it would only stay running if I kept my foot on the gas. Every time it stalled, it required a long crank to restart, and it would often start and immediately die unless I gave it throttle.

Now it won't start at all—just cranks. I suspected the fuel pump because there is absolutely no fuel pressure at the Schrader valve on the rail. I replaced the fuel pump, but nothing changed. The fuel filter is new, the relay tested good, the fuel pump wiring has power, and I can hear the pump prime. The pump also appears to be moving fuel.

The fuel pressure regulator is under the intake plenum, but since I have zero pressure at the rail, I'm not sure it's the cause. I didn't find any fuel leaks under the truck. One odd thing is that I can smell a slight fuel odor while cranking.

Any ideas on what could cause zero fuel pressure at the rail despite a new pump, good relay, and power to the pump?