[old_master]

Key on, engine off, fuel pump running, fuel pressure must be 60psi to 66psi. After the pump shuts off, pressure must remain above 55psi for 3 to 5 minutes. GM does not publish any "engine running" fuel pressure specs, (there are far too many variables involved).

As far as fuel pressure increasing on accelleration: perfectly normal. The fuel comes from the pump somewhere in the neighborhood of 75 to 80psi. It flows past the injectors and up to the fuel pressure regulator. The regulator is inside the plenum and uses a spring loaded diaphragm to regulate fuel pressure. They are adjusted to regulate fuel pressure anywhere from 60psi to 66psi. When fuel pressure overcomes the spring pressure, the excess fuel and pressure are returned to the fuel tank. The regulator has a port that is exposed to the pressure inside the plenum. When the engine is off, the port is exposed to atmospheric pressure and fuel pressure is at its highest, 60psi to 66psi. When the engine is running, vacuum in the plenum pulls against the back side of the diaphragm and slightly compresses the spring in the regulator and fuel pressure decreases. As engine load is increased, vacuum in the plenum decreases and the fuel pressure increases, back up to the 60psi to 66psi range.

If a shot of carb cleaner, (never use starting fluid), in the throttle body gets it started and running, that's a classic symptom of low fuel pressure. 3 fuel pumps in a year is a problem! The most likely cause is a poor ground for the fuel pump causing high resistance which will burn the fuel pump motor prematurely. The fuel pump grounds to the frame rail near the tank and should show less than 5 ohms resistance from the fuel pump connector to ground. Check the fuel pump connector carefully for burnt contacts or melted plastic. Most replacement fuel pumps come with a new connector and pigtail with heavier gauge wires that must be soldered to the original vehicle harness, don't use the crimp connectors that come with the fuel pump. Poor connections will cause low fuel pressure, along with premature pump failure.

The deal with the AC quitting and then the engine, might indicate an ignition switch problem. The ignition switch feeds several different circuits simultaneously and high resistance there could be causing all of your problems. Just something to check. It might help to connect the fuel pressure gauge and drive the vehicle until it acts up, that way you can see what fuel pressure does, and if that's the cause of the stall. Keep us posted.