'75 450SLC wont idle
 

I received a gift of a '75 450SLC that I drove from Arizona to New Jersey recently. It ran fine for a couple of weeks then it died on the road. It was/is running rich and wont idle without keeping the gas pedal down. I have replaced the Cold Start Valve, but it still continues to spray fuel long after the engine is started. I did find that the 104degree temp switch was cracked and put it back together (super glue). I have changed the fuel filter and I am getting fuel. Does anyone know what sensor switches might be causing the CSV to continually spray fuel? any help would be appreciated. The car is in great shape otherwise and was great to drive across country.

The cold start valve continually spraying fuel is the effect. The cause is probably the thermo time switch which senses coolant temperature and is located near the cold start valve. On some models the thermo time switch operates the cold start valve directly whereas on others it is via a relay. If yours has the relay this would be another possible cause. To verify that your problem is definitely being caused by the cold start valve continually spraying and to confirm that the valve is not the cause, you can simply unplug the electrical connector. This should stop the valve spraying and allow the engine to run properly. Likewise, unplugging the thermo time switch should also stop the problem unless the relay, if fitted, is the cause. Another common problem caused by the thermo time switch is difficult cold starting (due to the cold start valve not being energised for a short time when cranking). I replaced the thermo time switch on my 350SLC some years back due to this problem.