another linkage question

[tuultyme]

I have a quetion about the fuel linkage in my 1970 280SL.  My car is a USA version with the vacuum governor on the venturi control.  The engine idles at about 1000 rpm and drops to 600 rpm in gear(car's tach).  The injection pump rode measures 233 mm and this injector linkage rests against the injector stop, as mentioned in the BBB.  The car does have the hole in the right control shaft bracket.  Placing a 10mm tubing through this hole shows that the right control shaft is forward of the correct position.  While running the vacuum governor pulls the venturi to its idle stop (closed).  The Idle Speed Solenoid appears to function but while idling in park (automatic) the linkage does not come into contact with the idle speed solenoid.  In gear the two units just touch causing no effect.  What is the proper linkage adjustment to rectify this situation?  The engine starts fine and except for some popping on deceleration runs just a little rich.

Bruce Green 1970 280SL.

[Cees Klumper]

If I understand correctly, you are indicating that the linkages are adjusted properly, however the constant speed solenoid is not doing its job. You should leave the linkage adjustments alone, and rather adjust the length of the constant speed solenoid rod so it wil extend further - it should have a counter-locking nut which can be loosened to extend it. Try this first. It is also possible that it is worn, and lacks the 'power' to move the linkage, OR that there is too much resistance in the linkages (dry and/or worn joints, worn bronze bushings on the top control rod, worn nylon bushings, etc)

[tuultyme]

I do not believe the linkage is totally set up correctly.  There is not enough adjustment in the idle speed solenoid to make it work correctly.  The linkage does moves freely. I was hoping that there was some adjustment that I could try without messing up things too much.  There is just a lot of things that need to work together on these cars.

Bruce; 1970 280SL.

[Cees Klumper]

I used an unorthodox method to 'adjust' my constant speed solenoid when it did not have sufficient 'reach' to perform properly, as you describe: I just bent the metal holder than it sits on forward a couple of millimeters. This did the trick!

[George Davis]

Bruce,

as you noted, things have to work together, and the linkage and idle air/fuel settings sort of go together... especially if the throttle plate is misadjusted.  In your case, I think I would readjust the linkage, using the 10 mm tube and locating hole...assuming that moves things in the right direction.

First off, disconnect the throttle rod and check to be sure the throttle sticks slightly when it's against the stop.  If it doesn't, it needs to be adjusted so it sticks slightly... but this will reduce the amount of air going into the engine at idle, which may mean you need to fiddle with the idle fuel/air adjustments.  If you decide to go on, then:

Disconnect all rods, position the cross-shaft with the 10 mm tube through the locating hole and against the ball.  Make sure the pump arm is on its stop, and adjust the injection pump rod to fit.

Next, with the throttle against the stop, adjust the throttle rod to just fit.  Adjust the center rod and refit it; not quite sure of the details here as my car is a stick and has different linkage here.

Hopefully this gets things aligned so the compensating solenoid will do its job without too much bending.  It should be adjusted to give an idle speed of 700-750 rpm when in gear.



George Davis
'69 280 SL Euro manual

[tuultyme]

I discovered over the weekend that the constant speed solenoid is active all the time not just when the cars is in gear.  I have the automatic transmission with A/C.  Does anyone have a wiring dagram for this CSS?  It seems that something is grounding out the contacts.

Bruce; Blaugrun(green) 1970 280SL; IL

[Cees Klumper]

Bruce - I have a fully-detailed, color-coded (!) wire diagram for the 280 SL that was made by Joachim Ahlert, also a member here (forum name 114015). The wiring diagram that came with the owner's manual is not color-coded. It shows that the solenoid is governed by a relay. If it's ok with Achim, I can mail you a (color) copy of the diagram.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[bpossel]

I would like to bring this topic up again to the group...

Previously, I followed the posts (and the BBB) and set all of my linkages as outlined.  I still have some trouble with my “idle in gear” rpms.  My car idles at 800 in Park & Neutral.  When I put it in gear, the rpms drop to about 400 (a rough idle).  

This weekend I adjusted my vacuum governor per the instructions in the BBB.  When the car is running (with the engine running, the vacuum governor pulls inwards...) and in Neutral, the stop screw on the vacuum governor just rests below the small rod for the throttle plate (plate is fully closed at this point).  Using the assistance of my son, he put the car in gear, then in Neutral, then turned the car off, etc…  We did this many times as I had to adjust the nut on the vacuum governor that controls the spring, extending the spring out each time (also adjusting the small screw that resides on top of the spring, inwards to compensate).  The goal, per the BBB (I think?), is to have the vacuum governor slightly push up on the throttle plate and open it when you put the car in gear (I think I am understanding this???.  The BBB shows a gap of between 1.0mm and 1.5mm between the throttle plate stop screw and the small rod that opens the throttle plate when the car is in gear (?).

Anyway, now I still have the same problem, idle is too low when in gear….  Also, with the car turned off, and when I disconnect the throttle linkage rod, the spring on the vacuum governor forces throttle plate wide open…?  Before I started this adjustment, having followed the web posts, when I disconnected the linkage rod, the vacuum governor spring did not force the throttle plate open.  The spring simply remained compressed and the throttle plate remained fully closed and against the stop screw.

Is this the way it is supposed to work?  Any advice on how to correctly adjust the vacuum governor?  Also note: my CCS only activates when I turn on the air.  Otherwise, it doesn’t move forward when I put the car in gear…  The BBB states something about later cars and the ccs being only for air?

Thanks all!
Bob


bpossel
Memphis, TN.
1971 280SL
1997 E320

[rwmastel]

Bob,

I've not heard the term "vacuum governor" on this site before.  Can you elaborate on what this is?  Got any pictures?  Is it a distributor component, venturi or intake manifold component, or something in the fuel linkage?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[bpossel]

Hi Rodd,

I'll scan some info and post this evening.
Thanks,
Bob

quote:Originally posted by rwmastel

Bob,

I've not heard the term "vacuum governor" on this site before.  Can you elaborate on what this is?  Got any pictures?  Is it a distributor component, venturi or intake manifold component, or something in the fuel linkage?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

bpossel
Memphis, TN.
1971 280SL
1997 E320

[Cees Klumper]

Bob - it sounds like your problem may be in the wiring of the CSS - AFAIK it should be activated by the transmission being put in gear (forward or reverse) and not only by the airconditioning being turned on. Perhaps someone can verify/corroborate this on a US model with the vacuum governor?
If I am right, then your culprit should be in the wiring that activates the CSS, rather than the vacuum governor setup.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[bpossel]

Here are some diagrams that describe how I adjusted my vacuum gov.

Bob


Download Attachment: vacuum-gov1.jpg
20.5 KB

Download Attachment: vacuum-gov2.jpg
21.39 KB

bpossel
Memphis, TN.
1971 280SL
1997 E320

[rwmastel]

Thanks for the pics.  I don't have one of these on my car and didn't know they existed!  I guess the CSS (Constant Speed Solenoid) on my car adjusts both fuel and air while this device controls only air.  Looks interesting, yet complicated.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[tuultyme]

For problems in the wiring of the CSS look at the thread "Electrical Connections on 280Sl Transmission"  I had problems on my wiring of the CSS till I found out mine was grounded to the transmission instead of to the transmission pressure switches.

Bruce; 268Blaugrun(green) 1970 280SL; IL