Dell Inspiron No Video, No Post, Fans spin

After troublshooting an Inspiron 620 which was not displaying anything on monitor and not posting I decided to remove the motherboard from case and attempt to fire the system up with only power supply, memory, CPU, USB connections to board plugged in. I deliberately left the case power button jack disconnected and used the tip of a screw driver to momentary short the power pins on the board. The system booted straight away. It seems whenever the case power control pushbutton wiring jacket is connected to the motherboard, the system would only spin the fans and not successfully power up. I disconnected the black "loop" wires on the power button jack and it now starts up. Does anyone know what those looped wires are on the jack?