PeachParts Mercedes-Benz Forum - View Single Post

Tomguy · #2 06-26-2006, 06:57 PM

You should have ~12v at the cold start valve when trying to start cold - defined as engine temperature below 35°C. This may be higher or lower depending on current draw from the battery at cranking, or alternator running. The thermo-time switch is the main trigger for the cold start valve. It works by sensing water temp, and if it's too cold, its bi-metallic spring (like a thermostat's) snaps closed, engaging the CSV. Hence the "thermo" function. Once closed, the current passing through it heats up windings around the switch. This heat causes the switch to shut off at the right time - hence the "time" function. The colder your coolant is, the longer it will take for these windings to heat up and close the CSV. According to the manual it should be engaged for about 12 seconds at -20°C (and 0 at 35°C and higher). The relay is a cylindrical-shaped relay - not quite sure where it is on the 107 chassis. On the 108/109, I believe it's right behind the D-Jet computer.

These crappy starting conditions can arise from a vacuum leak, misadjusted air speed screw, misadjusted idle mixture, misadjusted throttle plate, or misadjusted throttle position sensor as well as a malfunctioning startup circuit. Also, your EFI trigger points can be crudded up (especially if the vehicle has been sitting a while) and may need a cleaning (DO NOT USE SANDPAPER!)

If you provide me with your email address (PM me if you like) I can send the D-Jet manual. It's meant for 108 and 109 chassis with the specific locations of some relays and whatnot, but you can use it to tune your system to factory specs. Adjusting my linkage, for example, exactly as defined in this manual made my throttle response INCREDIBLE.