Thermo-time switch on carbureted 911T?

[gsnow]

Hello all,
I just finished an engine drop and addressed some oil leaks around the triangle of death. In the process, was going through and comparing what I have on my original engine (1970 911T - Zenith carbs), to the Porsche PET, and I am stumped. It seems that I have the Thermo-time switch (sensor with 2 contacts threaded into the side of the breather cover). From what I can tell, there should not be a TTS on carbureted cars, only the E and S which are injected. Any thoughts as to why I would have this on my car? The PET also references an oil pressure switch which I don't appear to have. If the TTS was not original, that means at some point someone must have upgraded or modified the harness, breather cover, etc., and since this is only for injected cars, what could it be used for? Any input would be appreciated!

[edmayo]

Without researching this,,,,I think at one time Porsche did use a temperature switch to spray fuel thru the aircleaner tubes. After many back fires I believe this was discontinued and dealers advised to remove same. Jon B.?? Jim B. Gled Help here !

[AKAMick]

Like this? 70T, mine too, also has the air cleaner spray system,

[gled49]

If the wiring looks original to the tts, then it is. I’m with Ed, air filter housing cold start P circuits were installed on carb engines but found to be unnecessary because of accelerator pump circuits in carbs and they caused many fires. If you want it to look original, leave the parts and defeat the function. The parts would include tts, wiring, cold start valve (probably mounted to the carb base on a bracket), hoses to the valve and to the spray tubes in the air filter housing. Gordon

[AKAMick]

My 70T has the system, but it was defeated by unplugging the cold start valve behind the left bank Zenith carbs,

[gsnow]

My 70T has the system, but it was defeated by unplugging the cold start valve behind the left bank Zenith carbs,

Thanks guys. Everything on mine looks original (and I'm finding that most of the car is as well), so I will assume that is what I have. And yes the picture is exactly what I have. I don't know what the cold start valve behind the left carbs look like. Anyone have a picture of that? I did notice a bracket bolted to the back of the left carb with nothing attached to it (the bracket looks original, not like a rigged up piece), so maybe that was where the cold start valve was attached.... Thanks again for the help, this was my first post!

[gsnow]

There is a small hose running along the back of the air cleaner assembly, that I have never been able to figure out what it goes to. Could this be what the cold start valve was intended to feed fuel into? (trying to attach a picture from the parts diagram, not sure if it worked). It is part #18 on the PET diagram, shown as a 465mm hose at 4.5mm ID.

[AKAMick]

That hose feeds both spray tubes in each bank inside the air cleaner assembly, three holes are in each tube, one is directed into each throat, the left side air cleaner T fitting is fed from the cold start valve, which itself is supplied fuel by a reducing T fitting after the inline filter in the main fuel line to the hard fuel line that feeds the Zeniths. It took me awhile to understand this system as my engine came disassembled, my cold start valve had been defeated by disconnecting, as the wiring was wrapped in tape and tucked back into the main harness, but the system was intact and complete. The system reminded me a lot of a primer system for a small lawnmower engine, LOL!