Cold Start Problem

[Tigger55b]

Hard to start on cold morning. I have tested the "Cold Start Valve" and it works when I put a "hot" wire on it. However it is not activating when the starter is on. There is no current comming to the valve. What is the next component in the flow that would engage the cold start valve? My guess is the engine teperature sensor in the intake. How would one test that sensor? and where would you go from there if it tests ok? Almost forgot,, Its a 1990, 300E. Let me add that I have installed a switch (pushbutton) so that I can manually power the cold start valve while cranking the engine. At 20 degrees F, The engine starts on the first rev if I push the button. I don't want to do this forever, But it beats cranking it over and over and over! Well, I replaced the Temperature sensor. Made no difference, so we can eliminate that. Whats next? Anybody?

[Pili380SL]

I'm certainly no expert tech, but I believe the cold start valve is energized by one of the pins on the fuel pump relay. Some of those pins are only hot when an RPM (cranking) signal is sent by the ignition, but maybe someone can enlighten us on that. You might check for current next time you get it started. The coolant sensors I've tested are measured by resistance at different temperatures, across the pins on the sensor. If it's four pins, measure across diagonal pins. The resisitance should range from about 5600 ohms at 0 degrees C to approx 600 ohms at 80 C. You should probably get a service manual and double check me for your model.