which temp sensor...
 

Which temp sensor is responsible for telling the cold start valve if it is it is cold enough to activate the cold start valve or not? At what temp does the cold start valve begin to add extra fuel?
Car is a 1986 W201 190E 2.3-16v

For the M103 at least, the rear-most temp sensor with two prongs supplies temperature information to the engine management systems.

The single prong one supplies info to the temp guage in the car.
The triple prong determines when the auxiallary fan is on.

I don't know if the above applies to the 16v, but I hope that is a start. :)

1986 2.3 16v Engine temp. sensor. Tells the CFI control module to activate the cold start valve when the engine is cold.

http://i179.photobucket.com/albums/w...tempsensor.jpg

the meaning of cold in this instance is 30f or colder.

Does the temp sensor close or open to tell the cold start valve to activate?
ie. if it is above 30 degrees f will the sensor be open or closed?
Thanks

It's not a switch, it's a sensor that changes its resistance based on temperature. The brain uses the resulting reading to determine how long to fire the CSV.

Ok, sounds fine. At what resistance does the cold start valve firat operate (30 degrees) and it is more or less resistance when the cold start is activating? I am trying to test the sensor and the operation of the CSV.

Sorry, I don't have any info on your car. You might try a search, the sensor is probably similar across cars of that vintage.