How many pins are supposed to be hot in the fuel pump connector 1990 bronco II?

one, But it will not be "hot" just because the key is on, The ECM comtrols it, So it will only be hot for A second when the key is turned on then again after motor is running. If you are trying to test the power supply, You need help, use A test light disconnect the connector, Have someone crank the motor while you test the terminals, only crank for A couple of seconds at A time, You don't want to burn the starter up.