Cold Start Valve test '74 914 2.0
 

I removed the CSV and tested it today by connecting the gas line and the electrical plug, putting the CSV in a glass jar, and cranking the starter. The ambient temperature here is 90 degrees F.

The CSV didn't leak with the fuel pressure at 30 PSI, but it also didn't spray when the starter was being cranked. My understanding is the valve is supposed to spray for 10 seconds when the temperature is -4 degrees F or lower, and stop spraying when engine temperature reaches 130 degrees F. So I was expecting the valve would spray some but it didn't. Perhaps that's expected and the CSV does not spray unless you start the car when the ambient temperature is below -4 degrees F?

No idea where the 130F figure came from. The CSV only opens when the temperature is below a certain point, I think around 30F. Anything warmer than that in any way means the valve doesn't open. It will only ever open while the starter is cranking, as well.

So any time you're not starting the car, or any time the temperature is above around 30F, the CSV stays closed.

--DD

Thanks Dave, got it. Considering where I live, the CSV will never open. The testing demonstrated that the valve doesn't leak under normal fuel pressure. I'll re-install it with new gaskets and call it good.

BTW, the 130 F figure came from Harold T. Glenn's Volkswagen Type 3/Type 4 Fuel Injection Guide in the 914/4 Tech Notebook.

I figured that where and when I drive that the CSV would never be active or needed. I bypassed it so that I dont ever have to worry about dumping fuel in when not needed.

The line to the CSV seems like a great place to attach an on-board fuel pressure gauge. Where have other folks have installed fuel pressure gauges in the engine compartment?

That's where mine is!

--DD

The '74 has the 311 906 161 C thermoswitch (not a thermo-time switch). Actuating temperature from my D-Jet parts page:

311 906 161 C : -6 to -14 deg. C / 21 to 7 deg. F

The cold start system is designed so that the CSV will be actuated only during cranking, and only when the temperature of the thermoswitch is below the setpoint above. The thermoswitch and the CSV operate independently from the ECU.

https://members.rennlist.com/pbanders/DJetParts.htm