Constant Speed Solenoid

[TEJOLX47]

Hello Pagoda lovers,

Hope this message finds you Covid free.
I have had my share of posts and comments about the Emission Control System (ECS) in US cars.
This time, I have a different problem.
In my wiring diagram, the transmission pressure solenoids connect to the ECS.
However, my car has auto transmissions - and a Constant Speed Solenoid (CSS) - but I cannot find the CSS on the wiring diagram.
Any suggestions?
Thanks a lot
Francisco

[Pawel66]

The CSS is probably not shown on this diagram, if it is the one for US cars with ECS. Position 51 there is called "Idle Increase Solenoid", but it is a mistake, it is the 3way solenoid on gear box.

I think in the US cars with ECS the idle support related to selecting gears is governed by ECS, not CSS. CSS is there for Air Conditioning purposes and increases idle when AC is switched on.

Do you have Air Condition? If you do - it should be connected to CSS. If you do not - CSS were sometimes installed even not connected to anything. Then you have a spare CSS and are good $300-400 richer  .

If you need information how CSS is wired when it is operated by gear box - I can help you. I am not sure, however, if you have switches on gear box that operate CSS in this configuration.

[TEJOLX47]

Hi,

Thank you very much for the info.
I agree that component #51 on the diagram is the 3 position solenoid on the gearbox.
I do have Air conditioning but it is not connected to the CSS on any way. Can you tell me how should it be?
On the other hand, someone took a wire from the transmission pressure solenoids on the ECS and connected it to a weird relay that activates the CSS.
How would the ECS correct engine rotation when the transmission is engaged?
Do you have any useful diagram that I can use?
Many thanks
Francisco

[Pawel66]

I was studying a bit the CSS function/connections, but I stayed away from ECS and Air Conditioning - difficult to help.

There was a thread and a film link on how ECS is working, I will try to dig for it...

Check out:

https://www.sl113.org/forums/index.php?topic=29955.msg216979#msg216979

https://www.sl113.org/forums/index.php?topic=29007.msg210077#msg210077

[teahead]

I have Auto trans and AC.

My css isn't even hooked up.

[TEJOLX47]

Lol.
I shared the video on ECS, originally.
I have studied quite a lot of it but still din’t understand a few things.
But I’ll read the other post.
Thanks
F

[jeffc280sl]

the CSS is not part of the emission system. there does not appear to be any wiring between the emission and CSS subsytems

[TEJOLX47]

Thanks Jeff.
That is a relevant point.
Can you consider that the ECS is capable of correcting RPM?
If so, would it be via distributor's advance/retard?
Many thanks.
F

[jeffc280sl]

distributor timing is altered via a vacuum line from the two way valve and distributor.  Unfortunately this connection is missing from the diagram above. timing is altered by many factors.  if the emissions system is working properly it will not alter distributor timing in a pulsing manner.

the more i think about this maybe the css overlaps the emissions system and they share components.  looking through old posts i think the CSS is poorly documented

here is a wiring diagram for the AC system.  It shows transmission switches and the CSS.  The notes do not list applicability to the 280SL.  It gives some more insight to this issue

[Desertpagoda]

The CSS raises idle speed when energized. It does so buy moving its central core outward pushing it against the throttle linkage. It is adjustable . It receives its electrical signal at the same time and and from the same
place the A-C clutch gets its signal to operate. Do not expect the CSS to have the strength to push the linkage out, merely to hold it out.

[Pawel66]

Well, the CSS does push the linkage out, at least when it is hooked to gear box. If it does not, the engine stalls, you need to replace CSS if you find it not capable to push out linkage and hold it there.

As for ECS increasing idle speed - I never studied it. Often with ECS there is no CSS, that is why the conclusion was that it is ECS responsible for it. Not sure if it is true, so I took another look at the film (now I see you posted.

https://www.youtube.com/watch?v=-PzvtA03RGA

With the explanations (frames enclosed) I think idle is adjusted by vacuum, controlled by hydraulic switch and the two way valve (in essence). Idle adjustment for other purposes is controlled also by temperature switches. That is at least what I understand from the film.

[jeffc280sl]

I think we are getting to the bottom of interaction between the CSS and Emissions subsystems.  Both utilize input from pressure switches on the transmission.

The CSS is activated by transmission pressure switches and the A/C to increase idle speed due to engine loads from the auto trans and A/C.

The ECS is  also activated by input from the trans pressure and other devices.  The ECS uses these inputs to alter timing to reduce emissions under certain conditions.

[TEJOLX47]

Hi there everyone,

I have made some additional reviews of the ECS film and diagrams.
It is now a little more understood (except for the Speed Relay) and I will post an update of my explanation on the manual.
My conclusions are as follows (subject to further review :
1. CSS corrects the engine RPM when additional load is put into the shaft (by auto transmission or AC);
2. In US versions of the 280SL, the ECS should correct the RPM when the engine is cold (17ºC valve);
3. When the engine temp is above 17º... I don't know how it works...
4. The transmission solenoids in the ECS are only used to define one condition to cut the gas via the Fuel cut-off solenoid;
5. Consequently McGyver connected the transmission solenoids in the ECS to a relay that activates my CSS when transmission is in 1st, 2nd or R;
6. My CSS must have been installed to correct RPM when the AC is engaged; however, there is no connection from the compressor to the CSS;
It does not solve everything but is makes some sense.
After the pandemic, I will raise the issue to MB in Germany and share it would.
For those more curious, I attach the later version of my explained diagram of the ECS.
Cheers
Francisco

[jeffc280sl]

nice job with the wiring diagrams and logic.  i believe the input from transmission pressure solenoids are used by the CSS and ECS. 

[TEJOLX47]

Thanks for the comment.
I don't like to fix/change things without understanding them.
As far as I could see, Transmission Solenoids are used by the CSS in cars without the ECS.
Let's see the answer from the Classic Center

[jeffc280sl]

i think you're correct.  if you have an ECS you share pressure switches with the CSS

i have 3 subsytems on my 1970 280SL that share some sensors for inputs.

1.  cold start
2.  CSS
3.  ECS