Serial ports do not provide power, the pins are, in order:
1: DCD or Data Carrier Detect
2: RX or Receive
3: TX or Transmit
4: DTR or Data Terminal Ready
5: Signal Ground
6: DSR or Data Set Ready
7: RTS or Request To Send
8: CTS or Clear To Send
9: RI or Ring Indicator
None of those pins provide power to a device. The GND pin is to share a ground between signal levels so that the RS232 chip can detect the same levels as the device (called a ground reference).
You will need to
Improve your question[
^] and add details about the device and how you connect to it, perhaps it requires one of the other pins to go low, like DTR or CTS before it will send data.