You will need an ohm meter to check compressor pins. The pins form a triangle with the common pin usually on top. Measure ohms from that pin to the other two pins. The pin with higher ohms is the start pin, the other one, the run pin. The new start device pins should be labeled. Just make sure the run capacitor, if you have one, is wired between the run and start pins.

I assume you are using a universal start device, the original factory device will just plug in the right way, impossible to plug it in wrong. If you want to use this, follow the proceedure below.
The two pins with the highest resistance will be the run and start pins and the one left over will be the common. Measure the resistance from this pin to each of the other pins. The highest resistance will be the start pin, the lowest the run pin. The wires on the start device will be labeled s for start and r for run, and c for common. The run capacitor must be wired between the run and start pins.
When you plug the refrigerator in and the compressor starts but then stops, unplug it real fast as you made a mistake and the start winding will burn up.