Cold Start Valve
 

Hi All

My 124 with 102 engine just underwent a head gasket job. Now I find that it doesn't start so readily in the mornings. I believe that my cold start valve is triggered by the coolant temp sensor (its new, single pin type). I read that the fuel pump relay triggers the valve under 35 C. Is it just between the valve and the relay or is the ECU involved? I checked the valve with a multimeter and it checks out OK. I cracked the fuel line in and there was fuel.

Can someone help me understand how this works?

Regards

I think it's controlled by the ECU.

The way to check it is to remove the valve and hook it back up, pointing it into a jar. Pull the coil wire and have someone crank the engine. At summer temps you would only see a tiny puff of fuel if you see any at all.

Hi Chuck

Found out the problem. Mechanics interchanged the coolant temperature sensors for ECU and gauge. I changed both sensors for new ones but the ECU sensor was bad out of the box. The mulitmeter reading was all over the shop including being open at room temp. I replaced the old one which was OK to begin with and solved the cold start as well as wavering idle. So we can't trust all that comes out of a nice new box!

Regards

Nice Wrench!