Thanks Thomas. That looks much more comprehensive than just testing for continuity. I'll try to get it done this afternoon.

Andy

Tony, Thomas, as the TTS is easy to get to and the CSV is not, I just now tested the TTS individually using the below procedure from the discussion at the link that Thomas provided.

I tested a number of times, and even put the TTS in the freezer for about 10 minutes before several of the tests to ensure it was well below 113F.

The test light goes on in test #1, but it does not go on at all during test #2.

Is there any other bench test I should do on the TTS, or is this conclusive that it's not functioning?

Andy

http://forums.pelicanparts.com/uploa...1723670919.jpg

Andy

Then it seems to be bad ...even when it's already a newer electronic version, it has to pass test #2...

https://forums.pelicanparts.com/porsche-911-technical-forum/594010-thermo-time-switch-1978-sc-3-0-a-3.html#post12303246

New ones are pretty expensive...

You can also check if the CSV works by similating a working TTS by connecting W cable (bigger diameter) to ground while engine runs. If the valve is wirking additional fuel will be sprayed which makes mixture uberrich and engine will start to surge or, if it's way too rich, it will stall.

Thomas

Thanks Thomas, I'll order a new one.

Andy

As I mentioned before, make the crosscheck with the CSV, just to be sure that the CSV is working too. It may be clogged due being not operated a long time...
Here's the circuit in the car, W is not properly shown unfortunately..

http://forums.pelicanparts.com/uploa...1728945833.jpg

To operate the CSV the W cable needs to grounded, e.g. to the engine case.

Thanks Thomas, I didn't see yout CSV comment earlier.

OK, I'll ground the W cable, no problem. My car is an '81, I can just look in the pop-off valve for fuel spray during cranking?

Yes. Also possible with ignition on, disconnected security switch (to run the fuel pump) and sitting engine ... Never tried. Don't know if you can see something because of the 'spider' in the lower section of the airbox if it's present on your car.

Thomas

Thanks Thomas, I grounded the W cable but I did not see any spray under the toilet seat during cranking, all I could see was the stationary"hat" that's mounted above the pop-off valve.

I did smell fuel though, I think for the first time since I've messing around with this issue. Maybe that's a good sign?

Anyway, I'm not sure I should try to remove the pop-off valve so as to see through its mounting hole down to the spider (if my car has a spider). I would guess I'd have to take the airbox off to remove the pop-off valve?

Andy,

You can not see the fuel spray of the CSV inside the airbox for your SC unless you are SUPERMAN with an X-Ray vision. Try it and keep us posted. BTW, use test #2 procedure to test and evaluate your TTS.

Tony

Lol. I tried. Clearly no superman here! :-)

It was a nice thought but I could not see anything but the top hat over the pop-off valve.

Do you have a way to confirm CSV function with it in place on the engine?

Andy

Andy,

You have to remove the CSV from the motor and bench test it. Send your TTS & CSV to me and I could do the test and evaluation for you.

Tony

Thanks Tony that is very kind! But are you saying that the TTS test I did in comment #62 above is not conclusive that the TTS is bad?

Comment #62: https://forums.pelicanparts.com/12339073-post62.html

Andy

Hi Tony, the reason I asked you whether the (comment #62) TTS tests I did were conclusive was because I had already ordered a new TTS.

For additional info, I also checked my 45* C/9.5 s TTS's resistance against the <104* F values in the image below, and they were way out of whack.

Terminal G to ground was a little high at 46 ohms, however both the terminal W to ground and also the resistance between the two terminals was hopelessly off the chart, at >20M ohms each.

So, essentially no continuity.

http://forums.pelicanparts.com/uploa...1723594493.jpg

Andy

Also in preparation for doing a smoke/leak test I've cut away most of the very crispy and ancient sound mat that was laying on top of my engine.

Such an improvement already, now I can see back there!

Now I'm eyeing the never-functioning, never-used, very much in the way, A/C system...

Andy

Having gone through removing the CSV on my 1978SC I can give a tip on removing it. After several false starts I found the easiest way was to remove the heater ventilator and all the brackets in that area supporting cables and fuel hoses, particularly the one that partially covers the CSV. I had a cloth at the back in case I dropped anything and used a mirror to see what I was doing.

Roy

Andy,

The plugs to WUR, AAR, CSV, & AFS are identical except for the color and wires connected. It is held in place by a spring. Use the WUR for practice removal and get a feel how the plug/s comes off. Then try the AFS. Wiggle side ways with a slight pull to get it off.

Tony

Andy,

the resistance table to test the TTS is applicable the old electromechanic version of the TTS! The fully electronic version cannot tested in that way! It requires a bench test being wired & powered as it is in the car too. Unfortunately I cannot tell how to differ between both versions. They have a stamp of the production date, but also I cannot tell you when Bosch/Porsche moved to the new version. The Bosch pdf about the TTS is from 2017, so supposingly this is the time they changed...

Concerning the easier access of the backside (precisely front side of the engine with the power train) you can do a partial engine drop:
https://www.pelicanparts.com/techarticles/911_partial_engine_drop/911_partial_engine_drop.htm
https://www-elfertreff-de.translate.goog/showthread.php?t=22855&_x_tr_sch=http&_x_tr_sl=de& _x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

I recommend to also use two threaded rods to put instead both engine mounting screws left and right of engine backside. The threaded rods with tinyer diameter than the original screws. They prevent engine from falling down if the car lifter fails.

Go get the book from our host:
https://www.pelicanparts.com/More_Info/BK131569AP.htm
Also I heavily recommend the Haynes Manual for the 911 from 1963-1989:
https://haynes.com/en-us/porsche/911/1965-1989
Both won't help much in troubleshooting CIS, but they contain lots of information about the 911 and how it is constructed and what you can do on it.
Also the Bentley manual is highly recommended - even it's still got some faults:
Porsche Repair Manual: 911 SC Coupe, Targa, and Cabriolet: 1978-1983 Â*-Â* Bentley Publishers - Repair Manuals and Automotive Books

Thomas

Thanks Roy, that is very helpful.

Thanks Thomas, we bought the car around 2012, the TTS that I tested was in there when we bought it. I think it is old-style electromechanical, it looks like the TTS in the first photo below.

The second photo below is the new TTS that I ordered from Pelican, it looks quite different from the old TTS that's in my car.

My old TTS looks like this photo (except it's not cut apart)

https://cimg5.ibsrv.net/gimg/rennlis...390e7c884.jpeg

Photo of new TTS that I ordered from Pelican, photo is from Pelican website.

https://cdn1.pelicanparts.com/catalo...117-01-OEM.jpg

TY Tony, will do.

Andy