1971 S cold start soleniod question

[Gearbox]

I have a cold start valve ontop of the fuel filter that was wired to a button on the dash. I understand that this should be wired to the cold start thermostat some where on the engine. Any one know where this switch is located and a simple wiring diagram. I have all the manuals and master wiring diagram and it appears to elude me. Thanks Allan

[Eric911S]

Hello: I would keep it on the dash. When the thermostat that activates the cold start valve fails it will keep dumping fuel in the throttle bodies or the above them depending on the year. When you start it up and you get a backfire then up in smoke it goes. If left on the dash you can give a count of 6 holding the button then release then it should start in cold weather. Less if hotter weather. It is up to you. Hope this helps. Thanks Eric

[Gearbox]

Thanks Eric, Had the car for about 18 years and finally doing a full resto. Was thinking about returning this only non original feature back to original. But the original owner (Porsche Mechanic) had installed it but I never had to use it. But the push button looks very period and was installed very well. So I'll take your advice, thanks Allan

[Jeff Higgins]

There really is no cold start "thermostat" per se on these cars. That lead goes down to the "thermo-time" switch located on the little oval breather cover next to the MFI pump. There is a hot lead from the thermo-time switch down to the switched "+" side of the starter solenoid. Hit the key to send juice to the starter and it simultaneously sends it to that switch, which routes it to the solenoid on the filter console. After a few seconds, when the switch heats up, it shuts that current off. It does actually work pretty darn good when in good repair. The thermo-time switch is prone to failure, but they are available (if not expensive) if you really want to go back to fully original. All of these wires, by the way, kind of dissapear into the harness, so they are probably still there. You cannot mess up on the connections to the thermo-time switch, either, because the spade connectors are two different sizes. Hopefully some one didn't cut them off.

[Gearbox]

Thanks Jeff, looking at the factory manual and was unable to find it. Guess I'll pull it out and test it to see if it works then decide whether to hook it up again. But at least, if I leave it on the dash, I would wire it up much better than what it is now. Thanks Allan