The engine coolant temp sensor provides feedback to the ECU.

The ECU richens the mixture on a cold engine to assist startup.

If it's screwed (no pun intended), you will have difficulty starting coz the mixture will be too lean.

To test the sensor, pull the connector off and use a multimeter (set to test resistance) on the diagonally opposite pins.

You should approximately get the following resistance values corresponding to the temp just for your info :

6000 ohm - 0deg Celcius
3000 ohm - 20deg C
1300 ohm - 40deg
600 ohm - 60deg
300 ohm - 80deg
200ohm - 100deg

The pin assignments are :

1 Distributor ignition temp sensor
2 CFI temp sensor
3 Engine ground at intake manifold for distributor ignition system
4 CFI control module ground

At this point in time, you should check the resistance since the engine doesn't start and is cold. You should get a value "big" value corresponding to the ambient temp in your area.

Mine checks out at around 2000 ohms and it's very warm/humid where I live (around 30deg).

Hope it helps.