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914World.com _ 914World Garage _ Name this sensor

Posted by: Rand May 22 2006, 03:13 PM

Under plenum, passenger side. Is this a temperature sensor? What exactly is it called?

I have searched the Haynes, Brad Anders stuff, etc., and have never been able to find much information on this puppy.

I think I need to test it... Hot or cold, I cannot detect a difference in performance or running quality with it connected or disconnected. My car runs great with or without it. Obviously it's not as critical as the CHT or the intake air temp sensor in the top of the plenum. What exactly does it do?

How do I test it? Short or resistance across the terminals? To ground? What values are normal?

Any info or testing tips would be appreciated.

Attached image(s)

Posted by: lapuwali May 22 2006, 03:28 PM

That's the thermo-time switch, which grounds the connection if the temp is below a set point (90dF, I think) for the first N seconds (8-10). It's energized through the cold-start injector, which is only powered while the engine is cranking. So, while cranking, if the engine is cold enough, for the first few seconds only, the cold-start injector will open.

Posted by: Rand May 22 2006, 03:34 PM

Thanks James. So if my cold start injector is gone, this is useless?

Posted by: lapuwali May 22 2006, 03:35 PM

Yes. It's not used for anything else.

Posted by: Rand May 22 2006, 04:00 PM

Thanks. Ok, I'll test it and put it in my spare parts collection in case I run across someone who needs one someday.

Posted by: bd1308 May 22 2006, 06:49 PM

I thought it only was activated when it was below 40˚F

b

Posted by: Dave_Darling May 22 2006, 06:54 PM

There are TTSes (actually a misnomer, the "time" function didn't get added until later) that have different "set-points". Most seem to be in the 40 degree F range. Colder than that, and the sensor will short its single connector to its threads. (Those would normally be grounded through the manifold to the crankcase.) This provides a ground for the Cold-Start Valve (CSV). Without a ground, the CSV will never open so it won't squirt fuel into the manifold.

Power to the CSV is provided by the yellow wire that also goes to the starter. Without power, the CSV will also not open.

So the CSV can only open if two things are true at the same time: If is is below ~40dF, and also if you are cranking the starter. It is closed (or should be!) at all other times.

--DD