[cmonref]

The switch on the front side (the side AWAY from the rear bumper) of the airflow sensor detects whether the sensor is at rest (no airflow, engine not running) or has been raised by airflow (engine running.) If the sensor is at rest, the switch prevents the fuel pump from operating. If the wires are unplugged, they see an open circuit, keeping the fuel pump from running.

With the plug still in place and the wires pulled from the plug, if the wires are connected, the fuel pump will run.

All of this happens AFTER the engine starts. During start, power is provided to the fuel pump thru a "starting" circuit in the fuel pump relay. After start, power to the fuel pump goes thru the "run" circuit in the fuel pump relay. If the relay does not "see" the engine running (airflow pushing the sensor up, switch closed to connect the two wires), it will release -- and the fuel pump stops.

The purpose of the "run" circuit is to prevent the pump from operating if a fuel line breaks -- such as in an accident or just by dumb luck. If the engine is not running, who needs fuel?