elu,
sounds like a good plan.
vash,
correct, it isn't a choke..it's nothing more than giving you a physical link to the accelrator pedal for start so that you don't have to hold the gas pedal down with your foot. whoda thunk it??
ryan

Ryan and Ray,

Thanks for the help! I'll take a look this weekend and see if I can get my throttle microswitch wired up correctly.

The throttle lever replaces your foot on the gas pedal. From what I recall that is its only function, it opens the throttle body butterfly and allows the car to warm up without stalling. In 78 it was replaced by the Aux Air Regulator which combines the virtues of electrical and mechanical technologies in a way that only the Germans and lionel trains could have imagined. The cold start valve operates when the starter circuit is engaged and sends 12 volts up a solenoid on the cold start Injector. There is a two pin connector on the Cold start injector. The other wire from the injector goes to the thermotime switch. From the switch it goes to ground [thru the engine case]. The thermotime switch is your basic dumb heat sensitive switch. When it is cold the switch is closed it completes the circuit and allows the cold start injector to squirt. At a preset temperature it opens { like the wall thermostat on your house heating system} and prevents the Cold Start Injector from squirting fuel. An easy test for a defective Thermotime switch is to attach the wire that goes to the switch to ground with a clip lead. Now try to start the cold car. If it fires right up then the switch is bad. If it still doesn't fire up there might be a break in the wiring, the connector on the cold start injector might not be seated or the Cold start injector might be toast. Its not an expensive part just a major pain in the arse to R&R.

"correct, it isn't a choke..it's nothing more than giving you a physical link to the accelrator pedal for start so that you don't have to hold the gas pedal down with your foot. whoda thunk it??"

"The throttle lever replaces your foot on the gas pedal. From what I recall that is its only function, it opens the throttle body butterfly and allows the car to warm up without stalling."

No, for the early CIS cars these comments are incorrect or partially incorrect.

First of all for the 1973.5 and 1974 (and maybe 1975) CIS systems the hand throttle lever must be pulled all the way up (closing the microswitch) or the CSV will not function.

Second the CSV acts like a "choke" did in the old days enriching the mixture making starting easier.

Third the CSV only functions while the starter is turning; once the starter stops turning it does nothing for or to subsequent running (unless it is leaking fuel due to being defective).

4th, the hand throttle lever does also hold open the TB butterfly for increased idle speed to allow the engine to warm up.

5th, in 1974 and later cars the thermo time switch will cut power to the CSV if the engine is warm thereby eliminating it's functioning when the engine is warm.

Jim

jim,
i agree with the points you mention. these things definitely do occur when you pull up all the way on the hand throttle. my simple point is actually that these things you list WOULD ALSO HAPPEN if your hand throttle were missing by holding down the accelerator pedal a little bit. in other words, the hand throttle physically accomplishes all of 'these things' via the simple act of moving the throttle cable. sooo..what i'm trying to say basically is that i'm right..and that you're even more right..:)
ryan

Bigchillcar's description of the hand throttle on early CIS cars is entirely correct. The hand throttle is just what it says - simply a way to hold the engine revs steady without using your foot or a brick.

The cold running enrichment, or choke function is done by the warm up regulator. It is the WUR that enrichens the mixture when cold by reducing system pressure. Reduced system pressure allows a greater deflection of the air plate at the fuel distributor for a given air flow. The greater deflection adds more fuel for that given amount of air (which is what a choke does).

The WUR closes progressively with an increase in temperature, just as we would use a manual choke. As it closes, it increases the system pressure, until at normal running temperature it sets the pressure and therefore mixture, at optimum for a warm engine. This is why the cold pressure and the warm pressure checks are always the first step in diagnosing CIS troubles.

The microswitch on the throttle stop only needs about 1/16" rotation of the throttle to activate, so lifting the hand throttle just a little - about 1" - activates the switch (I listen for the click of the switch before I start from cold to tell me that the throttle is open enough to activate the cold start injector). At this point the throttle is also open enough to give me about 1200 revs when cold. I adjust the range of movement of the hand throttle on the accelerator cable stop between the seats.

I make this point on the function of the hand throttle only to allow a better understanding of the CIS system. The CIS set-up seems to have a very bad reputation on this BB which I think is unwarranted.

I believe that this has come about simply because we do not fully understand how the system works. As a result we give up in frustration when it goes wrong and say that the system is flawed.

In the end a better understanding will save all of us a lot of that frustrationand expense.

"The microswitch on the throttle stop only needs about 1/16" rotation of the throttle to activate, so lifting the hand throttle just a little - about 1" - activates the switch"

If this is the way your system operates it is out of adjustment (see the factory shop manual) as it should not actuate the microswitch until the hand throttle lever is fully pulled up. In the 1973.5 T CIS systems there is not a thermotime switch in the CSV circuit so an mis-adjustment like this results in the CSV being opened whenever one is slightly above idle.

I wrote the CSV acts like a choke for enrichment for starting I didn't mention anything about subsequent running enrichment which indeed the WUR indeed accomplishes.

Without the CSV enrichment these early CIS cars are nearly impossible to start (hot or cold) if one is keeping one's foot off the gas pedal during starting. Using the gas pedal to start risks blowing these early CIS air boxes even if a popoff valve is installed.

Cheers, Jim