What exactly is the problem on the car?
The cold valve only works at certain temperatures and for a few second.
To test it you can simulate a resistance on the coolant temperature sensor plug (10 kohms). You can measure the voltage on the plug of the start valve. Should be at least 10v for 5sec during start. If you just want to test valve and not the whole system you can apply 12v and check if it opens by spraying fuel into a container.
Just be careful so you don't start a fire.
The proper procedure is to simulate the resistance with ohm decade or some resistors, but these are hard to find sometimes.