2-Way Valve

[bpossel]

Happy 2007!

This time of year, as the temp is a bit cooler in Memphis, I continue to try and resolve my cold idle issue.  All: linkage; timing; 17 degree switch; vacuum lines (new); thermostat in IP pump; IP pump filter; ... have been checked, and are ok.

The issue is that when the car is started cold, the idle rpm is low, ~500rpms, and once the temp reaches ~179 degrees, I hear a "click" and the rpms jump to ~800.

When I start the car cold, I notice that if I disconnect either of the 2 vacuum lines going to the 2-way valve, the rpms jump to ~800.

 :?: Can someone help me confirm that my 2-way valve is hooked up correcty (vacuum lines & power/ground cable)?  The BBB has a nice diagram (see below) for the vacuum lines, but its for the carb system (not our beloved injection system).

I have read a lot of good posts on cold idle, but did not find any info on the 2-way valve.

Jeff/Bruce, I believe you sent your Speed Relay to Beckman in NC.  Has anyone else used them?  Any other suggestions for vendors on Speed Relay and Relay Box?

Thank You!
Bob

Download Attachment: 2-way valve.jpg
57.03 KB

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[al_lieffring]

hey Bob

it's been a long time since I've been under the hood of a 70 280sl, but from what I remember it sounds like your solenoid is working the oposite of the way it should. The timing should be advanced when there is no vacuuim.
I remember that at warm idle the timing should be set at 0deg with the vacuuim connected. The timing should advance to about 10 btdc when the vac is disconnected. Grounding 17deg switch should advance the timing, so should grounding the 100deg switch on the thermostat housing, the rpm controll box should be advancing the timing at somewhere around 2000 rpm.

It sounds like you may have the wrong vacuuim solenoid, does it look like the one in the diagram that is going to the dashpot on the carburetor? The 3 way valve shown on the distributor lines was not used on fuel injected engines.

al

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[bpossel]

Hi Al!
Here is a picture of my 2-way valve.
Download Attachment: 2-way-valve.jpg
39.9 KB

The ground is connected to the inside post.  The inner vacuum connection goes to my distributor.  Does all this look, sound correct?

Thanks!
Bob

quote:Originally posted by al_lieffring

hey Bob

it's been a long time since I've been under the hood of a 70 280sl, but from what I remember it sounds like your solenoid is working the oposite of the way it should. The timing should be advanced when there is no vacuuim.
I remember that at warm idle the timing should be set at 0deg with the vacuuim connected. The timing should advance to about 10 btdc when the vac is disconnected. Grounding 17deg switch should advance the timing, so should grounding the 100deg switch on the thermostat housing, the rpm controll box should be advancing the timing at somewhere around 2000 rpm.

It sounds like you may have the wrong vacuuim solenoid, does it look like the one in the diagram that is going to the dashpot on the carburetor? The 3 way valve shown on the distributor lines was not used on fuel injected engines.

al

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[al_lieffring]

Yes, the center vacuuim port goes to the distributor, and the polarity of the two electrical connections shouldn't matter.

At warm idle does the timing advance when the vac line is removed from the distributor?

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[bpossel]

Al, thanks for sticking with me on this!

When I disconnect the vacuum line at warm idle, there is no noticable change in rpms (by ear).  I would assume that I could hear the advance when warm, like I hear when cold and I remove the line?
Any ideas?
Bob

quote:Originally posted by al_lieffring

Yes, the center vacuuim port goes to the distributor, and the polarity of the two electrical connections shouldn't matter.

At warm idle does the timing advance when the vac line is removed from the distributor?

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[jeffc280sl]

There is a better explanation of the emissions system on the MB CDrom.  Chaeck under "Engine Checking and Adjustments"  Under that heading there is a topic on US Exhaust Emissions for 1970-71 with auto trans. This will be a good start for you on trouble shooting the system.  Check under my previous post for the 17 degree switch.  As I recall this switch should be closed when the temp is below 17 C.  Mine is broken in the open mode as I suspect many others are.  I have not been able to find a replacement.  My guess is that most peolpe just live without it's function.  Basically when the temp is below 17C this switch is closed taking the circuit to ground.  In the auto trans system this provives a ground to pin 2 of the relay box.  I've followed the circuit through on my manual trans system but not the auto.  After the ground on pin 2 some other relays come into play and eventually the two way valve removes vacuum on the distributor and it advances which has the effect of increasing idle speed.  The exact same effect occurs when you ground the 100C switch.  I suppose Mb wanted to change the distributor advance when the engine was cold and very hot.

What happens when you ground the 100 and 17C switches?  Just connect them to ground one at a time.  The distributor should advance in both cases and idle will increase as a result.

Jeff C.
1970 280SL 4-speed

[al_lieffring]

Next step would be to connect the vac directly from the manifold to the dist and check to see if the timing is at tdc, and set idle to about 800rpm then with the vac discnnected it should advance to 10 btdc and pick up the idle another 200 or 300 rpm.

Then reconect the solenoid, and unplug the 100 deg switch and the 17 deg switch to see if either of theses change the timing. At warm idle they both should be open (not grounded).

66 230sl
113-042-10-014715
904/396 blue, Ivory Tex
condition: not-as-rusty-as-before-bucket

[Benz Dr.]

Vacuum always goes to the centre port regardless of how many vacuum conections a switch over valve may have. I've found a lot of cases where the vacuum lines have cracks or holes in them or the rubber conectors are split or loose.
Put a vacuum on the whole system right at the throttle valve after removing the line from that port. It should hold vacuum and the distributor should move to the full retard position. You can verify this by removing the distributor cap. If the distributor isn't moving you may have a restiction in the vacuum lines or the switch over valve could be defective. If the system won't hold vacuum you need to repair any leaks. It has to be air tight to work properly. Very small leaks shouldn't be a propblem though as the engine can keep up with them.

Note: the switch over valve is common to later sedans. I've found them in 116 sedans and other models that use climate control systems. You have to find one that has only two ports at the bottom. Some have three with an xtra port on the top. These probably won't work.
Put 12 volts to the two pins to see if it clicks. If it doesn't, it's defective. I had a case where the valve worked and a signal came at 2,200RPM yet it still woldn't work. I suspected that there wasn't enough voltage to trigger the valve but could never figure out how to make it work. Probably one of the relays were shorted out or something like that. Oddly, the engine will still run strongly without the the extra timing advance due to the way the distributor moves right off idle. You will loose some mide range and top end performance with a loss in fuel mileage.


Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[jeffc280sl]

Bob,

Here is the way the 100 and 17C switches control the two way valve


17C switch

A) is normally ground. Above 17C it should show open.  With a ground from the 17C switch you should see a ground at pin 5 on the socket for the larger eight pin relay.  When pin 5 on the relay sees ground it will provide +12V to pin 7. (Note: Pin 7 and pin 4 on the eight pin relay are wired together.)

B) Pin 7/pin 4 are connected to pin 1 on the six pin speed relay.  Pin 1 is connected to the +side of the two way valve.  When it sees +12V (from pin 1 of the speed relay) the two way valve will close
and ignition will advance.  

100C switch

A) is normally open. Above 100C it should show close.  With a ground from the 100C switch you should see a ground at pin 6 on the socket for the larger eight pin relay.  When pin 6 on the relay sees ground it will provide +12V to pin 4. (Note: Pin 4 and pin 7 on the eight pin relay are wired together.)

B) same as the 17C switch

If you take this relay/switch setup one step at a time you can figure out where you may have a problem.  Try grounding the 17 and 100C switch wires and see if you get power on the pins as mentioned above.  If you do this will tell you that these two parts of the system are working.  Then we can move on to the hydraulic switches, rpm sensor switch etc.


Jeff C.
1970 280SL 4-speed

[bpossel]

Thanks Al, Jeff & Dan for your replies and suggested things to check.

Here is what I did today:
1.  Ensured idle speed (800rpm) was set to 0 TDC.  Could not test/set other ranges (1500, 3000rpms) because I didnt have my helper today.
2.  Tested the 2-way valve, per Dans suggestion.  Hooked it up to the battery directly and was able to have it click.  So 2-way valve is good

I will do the other tests that Jeff mentioned this coming weekend and will post results.

Thanks again!
Bob


bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[ja17]

Hello Bob,  

Sounds like your system is working.  

Here is the factory Suppliment for these emission engines. The bulletin includes   diagrams, description and test procedures.

Enjoy!
Download Attachment: ignch1.jpg
75.7 KB

Download Attachment: ignch2.jpg
52.51 KB
Joe Alexander
Blacklick, Ohio

[Benz Dr.]

Always use a volt meter to test the relays or you could damage them. The plug in connector at the two way valve can be tested with a test light. You should have 12 volts over 2,000 RPM.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[bpossel]

While living in the garage this weekend, in-between replacing the steering gear box (had to rest in between the weight lifting exercise with the heavy weight of the box), I had a chance to test my 17 degree switch and see if this is where my cold idle issue really is...

With the help and suggestions from Jeff and many others, and with my refurbished relays, I removed the back cover from the 8 pin relay connection and grounded pin 6.  When I started the car cold, idle rpms jumped to ~900.  When I disconnected the ground from pin 6, the idle rpms dropped down to ~500.

So, ist appears that my 17 degree switch has failed in the open position.  What is so cool is now I know what the cold idle issue is and it can be fixed.  Hopefully another problem solved soon...

Bob

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[jeffc280sl]

I've tried to locate a 17C temperature switch without any luck.  I suspect many cars operate as ours do with a broken switch.  Lets see if we can find a solution.  If VDO doesn't make one we may have to look elsewhere.

Jeff C.
1970 280SL 4-speed

[bpossel]

Hi Jeff,

SLS has one listed on their site.  Item #74 on their "electric engine control page"  74 Euros.

I am also going to check the dealer...

Bob

bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320