I tried many ways to plug it but what is weird is that the wire's colours of my connector doesn't look like an ATX so, I attached an image of an Compaq connector (apparently what I have because the colours are the same and the pin 8 is inexistent). When the power supply is connected to the motherboard, I use the green (+5V AUX) and the white wire (PS/ON) to start the power supply. When it's not connected to the motherboard, I put a jumper wire from a brown wire (+3.3V) to the grey wire (0V AUX) and when I connect the green wire with the white one the power supply starts for a seconds and stops (With and without a load from a red wire (+5V) to a black wire (0V)).
All videos and tutorials I saw are with ATX connectors and it seems so easy... This article Use a Compaq 200 Watt Power Supply (PSU) as a second power source | Experts Exchange is the closest I found to my connector but still not the same because on the pictures I can see a purple wire and I don't have this wire.
My power supply is a PDP116P from compaq...
