Thermo time switch bad? many questions

[sammyg2]

I've been looking at the electrical schematics and searching old posts but I still dont have an answer for this question:

I tried to figure out how my thermotime switch works, I know that power is supplied to one side of the cold start injector from the starter circuit and is grounded through the thermo switch, right?

One side of the switch has power to it that acts as a heater to warm it up, right?


I tested my switch, it 24 ohms on one side when cool, the other side still has no resistance.

I tested it with the wires disconnected when the engine was warm and one pole showed 98 ohms resitstance to ground, and hte other showed 60 ohms.

Does that sound right?

I'm trying to learn all about the system on the car.
It starts fine but I've never tried to start the car below 55 degrees F.

If someone wanted to be able to run the cold start injector on demand, what would it take? I'm thinking a switch that not only supplies 12 volts to one side of the injector but also grounds the other, would that work?

Edited for accuracy.

[vash]

ok, i dont have a tts, but i just read about it. let me paraphrase:
if the CSV is not working do this:
make sure car is cool, below 95 deg. disconnect CSV, and connect a test light across the terminals. crank motor, light should come on. that means wires are ok. then take off the fuel line to CSV, and crank motor, if gas comes out, your CSV is bad. if not, you have to move upstream to look for blockage.
if the test light doesnt come on, then: make sure you are below 95deg. connect one of your test light terms to positive 12v. then probe the the harness of the CSV. one should light the bulb the other will not. if neither lights the bulb, the check the wire going from the CSV to the TSS for an open circuit. check the one that goes from TSS to ground also for an open circuit. if all is good replace TSS.

i dont think, you can make the CSV work on demand. you need the TSS to be below 95, the starter cranking in order to work.

are you having a hell of a time getting to the CSV and related components? how are you reaching everything?

[sammyg2]

On my car it's not too bad getting to all the parts I just have to pull the turbo pipes and air sensor and throttle body boots off, then I can reach all kinds of stuff.

I was thinking of using the CSV as a source of supplimental fuel under boost kicking in at 2 or three pounds, looks like I'd have to have a pressure switch that at 3 psi would supply 12 volts to the CSV and ground the other lead from the CSV at the same time.
Prolly too much hassle.
I have a spare CSV, I'll prolly just install it in the turbo discharge piping with fuel from the control pressure sustem and power it with a hobbs switch.

[vash]

that would be slick!

[tsuter]

Sammy You just have the Hobbs activate a DPST relay to fire the CSV. The problem is fuel distribution when there is no air inside those internal runners. normally air comes thru the AAV routing when cold - but not when hot. So your fuel will just pool in the manifold runners w/o air.

[sammyg2]

Hmmm, that makes sense.

OK, no matter how I try to weasel out of something, I always end up doing it.
At least I learn when I try to find a better way that doesn't exist.

[Early_S_Man]

Sam,

There are two terminals, 'G' and 'W', and case ground ...

Your reading of 24 Ohms is OK for the heating element at room temp ...

Per the diagram below ... note the Yellow wire to Terminal 'G' ... that is the heating element.

The other Terminal, 'W' is a switch contact controlled by a bimetallic temperature sensing element. It should measure zero Ohms whn below 112°F, and be open - infinite resistance to ground when above 112°F.

[sammyg2]

uh oh.
On my switch the "W" terminal was zero ohms cold but when warm only got up to 98 ohms. I may have to test it again after I get the engine really hot, but I know it was over 112 degrees F.

Any idea what effect that would have on the cold start system if any?

I've given up on using the CSV for other purposes but i might as well make sure the car is running the way it should, even if I usually don't need a cold start.

[Early_S_Man]

Sam,

That sounds like a toasted/sticking Thermo-Time Switch! Hard to say what side-effects it might cause for the CSV with that much resistance in the circuit.

[fintstone]

From CIS Primer:

Thermotime switch:
This switch allows operation of the cold start valve at engine temperatures below 45 Degrees C (113 degrees F) and then only for a few seconds during starting. Power is applied to the switchs internal resistor from the starter. The internal resistor heats a bimetallic strip which interrupts the current flow on the ground side of the cold start connection. After engine warmup, engine heat is responsible for holding open the bimetallic strip, so that the cold start valve will not energize when the starter is operated on a warm engine. Also, after several unsuccessful starting tries on a cold engine, the internal resistor will heat the thermotime switch and cold start valve operation will be inhibited until the switch cools.

Failure modes: An open circuit at the internal resistor will allow the cold start valve to operate an excessive amount of time if the engine does not start soon on a cold engine. An open circuit at the bimetallic strip in the switch will prevent operation of the cold start valve.