Do I need a new Thermo time switch(TTS)?
 

I gave my car a tune-up and it lead to a cold start problem (see thread here).

I disconnected the yellow wire to the Thermo Time Switch and now my cold starting issue is gone. It starts right up and is happy as can be.


From what I understand about the TTS, what I am doing now that the wire is no longer connected is that the CSV is sending extra fuel to the engine. Now that the TTS never tells the CSV to stop I'm driving around with a six cylinder car using seven fuel injectors.

I want to get my car sorted- will replacing the CSV allow me to reconnect the yellow wire and get my car back in top shape?

TIA

Edit: This is for a 1980 911sc

Interesting read: http://forums.pelicanparts.com/porsche-928-technical-forum/589524-thermo-time-switch-questions.html

Sounds like it only engages during startup. If your issue is only during this period... I'd replace it.

the yellow wire is the power to the CSV and the TTS. the yellow wire is the heater portion of the TTS. it is there so that if you do a prolonged start it will not flood the engine. with the yellow wire removed from the TTS, the CSV will ONLY come on while crankiing, but it will come on everytime, even when hot. that could mean too much fuel when hot and make it hard to start or foul a plug.

sounds like the heater element in the TTS may be shorted or have less resistance than the CSV.

to anaswer your question i would say no .. the CSV is doing what it is told to do ( see above ). A new one will do what it is told to do also .. :)

Nice write up by T77. That has to give you comfort your cold start switch is at least kinda sorta working and you are not pissing all kinds of gas through your system non-stop.

I did once pull out the Cold start valve only a few inches (left it connected and pointed at a rag. Rigged a video camera on a tripod and turned the key for a second. OMG that thing lets loose a fuel spray. I don't think the car could even run at cruising speed let alone idle if left to spray full time.

Maybe it could be used as a fuel supplement when we all NO2 our CIS cars. :-)

or maybe to dump a little extra fuel into the exhaust of my 930 to get more flames. my luck the car would be in flames.

[QUOTE=T77911S;7503965]the yellow wire .......it is there so that if you do a prolonged start it will not flood the engine. QUOTE]

Micro hijack question for T77911S or anyone who knows:

CIS cold starting on bitter cold day vs 80 degree day. Let's say one long five second crank.

Will the TT switch cut off the CSV before the starter is disengaged if the ambient temp is warmer?

Another way to ask is was there a duration range engineered into the TT switch that will only let it spray for a second for cold start on a 80 F day and maybe three seconds on a 50 F day?

I have understood it to be spraying all the time when cold if the starter is engaged unless a 120 F day. Cut off temp is somewhere near 100F or close.

I am asking as The 70's Jaguar XJ12 models have a Lucas D-Jet (licensed from Bosch) system that the TT switch tapers off the duration. Gave me fits trying to trouble shoot if a touch warm. BTW - the problem was simply a loose connection on the injectors. Can you imagine that on an old English car?

Bob,
The TTS is a simple switch on the 911 version.
Just like a thermostat. On or off only.

Thanks

Thermotime switch.........
 

Disconnecting the yellow wire from the TTS disables the heater (TTS). A good TTS operates at 113 deg and below. Unless you are in Death Valley, you might not need it sometimes. Remove the TTS and bench test it for its operation. Test and confirm. Stay away from guess-work to get to the bottom of your problem. Have you checked the fuel pressures, air leaks, and ignition timing?

Have you inspected and checked if the CSV is leaking or not? Have you double checked the ignition timing using an inductive timing light? Even a bad TTS which hardly go bad does not make sense to me regarding your troubleshooting. There are too many unanswered questions or information needed to be addressed. I intentionally refrained from your posts and watched from the sideline. But can't bear to see you struggle to diagnose the problem/s.

I really like to you to succeed and like to assist you but I have no clear idea or direction of your tests if any. Keep us posted.

Tony

you know i was going to bring up the point of how long it will run the CSV and suggest that if tony piped in HE would know. it would also depend on how cold it is.

what has always intrigued me about CIS is the engineering that must have gone into it. cold starts, hot starts, extreme cold. one adjustment and it sets the mixture for the entire RPM range and starting.
if it takes too long for these cars to crank, there is something wrong. fuel pressures, ignition, AIR LEAKS, mixture adjustment and even engine related issues.
my 77 with 120k+ with VERY bad rings AND valve guides still started right up.

Tts.......
 

Ty,

Unless the TTS is stuck CLOSED or grounded would the CSV operate above the operating temperature of the TTS (113 deg. and below). The CSV valve circuit is grounded via the TTS and if the circuit is open (no ground) the CSV would remain disabled. So instead of assuming to many things, we need to test and confirm the condition of the TTS and CSV.

Tony

Fair post Tony.

I strongly suggest the timing double check but a CSV leak test is secondary from my viewpoint. However, you may have clearer thoughts on why this should be done.

The test of the TT switch on the non heater side terminal is to make sure it grounds when cold and that 12-ish volts are at the wire when cranking.

12V travel through the heater wire at the same time as through the CSV power wire. Correct? So that is an easy test.

How would the yellow wire terminal be tested? Couldn't you test the ground side with the yellow wire attached to the heater terminal to see if it breaks ground as soon as cranking starts?

I agree that he should not spring for a switch until basic due diligence is performed.

Edit: Sorry timing overlap