[47silver]

if you raise the arm and the injectors spray you have good pressure. If when the car is warm it runs good then i dont think that the cold start valve is leaking or it would cause you to run very rich.
On my 1975 when the key is in the crank position (turning over the starter), 12vdc is applied to the cold start valve + side. The negative side goes to the thermo-time switch which is located on the back left side of the engine. The TTS allows current to flow to ground when the engine is cold and opens the circuit when the engine is warm.

To trouble-shoot:
1. Remove the plug from the cold start valve. Very difficult to get too and a royal pain. If you remove the boot it is a bit easier.
2. Use a meter, have someone crank the engine you should have 12volt to ground on one of the terminals. if so that is good if not then you have a wiring issue. I had the same problem and traced it to a bad connection at the starter solenoid.
3. If you have power you have to test the valve. You can remove the wire on the thermal time switch and put it to ground. when you crank the key, look inside the air box and you should see (75 air box) or hear it on the later ones with the manifold arrangments.
if you dont hear or see a spray then the solenoid on the valve is bad.
if you see a spray then i would say your thermal time switch is bad.