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1986 560SEL
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Discussion Starter #82
With the adjustment tower having been tampered with, the duty cycle readings while the engine is running are worthless with regard to their diagnostic value, of course … but not the other readings !
So, What readings would be valid for diagnostics? And why are the other readings worthless? I am sure you've explained this but...:rolleyes:. Every time I think I understand this, I get more info and more confused! Before I buy more parts and switch them out, even though the adjustment tower has been fiddled with, you are saying that it is still a very valid diagnostic tool, but limited...? I saw where you said the duty cycle should be run after changing out anything involved with the fuel system... would that give a new starting point per se, and then become the 'base line' measurement for further duty cycle measurements along the way? I'm sort of confused... can the duty cycle ever become valid once again for ALL measurements?

Wow on your apparatus!!! I know my limitations and I could never build and figure out how to hook up your device! But I can run a couple of wires from the interior to the engine bay! Even if it takes longer to test everything, I CAN do that!

Once again H.D., kudos to you for taking your invaluable time to go through all of this.
 

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1988 300CE
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Every time I think I understand this, I get more info and more confused!
Many a MB mechanic said exactly the same thing in the 1980‘s. … LOL ... Let‘s go through this step by step, covering all your questions. I‘ll probably become quite busy with other things in the upcoming days, but right now I still have some time for that.

There are several typical culprits for your car‘s symptoms. But I hope you don‘t mind that, instead of naming them upfront, I‘m using your thread to explain some systematic testing & diagnosing. … As I said in my first post, the easy to perform duty cycle test might already turn out to be very valuable in this case. ;)

For better clarity I'll once more list the six conditions under which to check the duty cycle:
1) ignition on (engine not running)
2) ignition on (engine not running) & air sensor plate halfway deflected (throttle closed)
3) ignition on (engine not running) & throttle completely opened (air sensor plate not deflected)
4) engine warmed up to full operating temperature & running at idle speed
5) engine warmed up to full operating temperature & running at ~ 2500 rpm
6) engine warmed up to full operating temperature & running at idle speed again

Since you probably don‘t have a duty cycle meter, respectively a multimeter that provides the duty cycle of the Lambda “off/on ratio“ (which in the service manual is misleadingly called “on/off ratio“ ;)) … do the measurements in ‘volt‘ with a simple multimeter, as already described in post #54, like this:
  • Set the meter to 20 VDC with the red lead in “V“ and the black lead in “COM“.
  • Then (with ignition switched on and engine not running !) take a reading with the black test prod in port ‘2‘ and the red test prod in port ‘6‘ of the diagnostic coupling X11. Let‘s call that reading “Vp6“.
  • Then move the red test prod to port ‘3‘ and take readings under the six conditions mentioned above. Let‘s call these readings “Vp3“.
  • Then (with the engine still running) take another “Vp6“ reading with the red test prod in port ‘6‘ again.
So, What readings would be valid for diagnostics?
Vp6 should be about the same as the battery voltage … both with “ignition on / engine off“ and with the “warm engine running“.

Vp3 under the above six conditions should be:
1) ~ 30% of Vp6 (in case of California car: ~ 15% of Vp6)
2) ~ 90% of Vp6
3) ~ 80% of Vp6
4) ~ 50% of Vp6 (fluctuating)
5) ~ 50% +/- 10% of Vp6 (fluctuating)
6) ~ 50% of Vp6 (fluctuating)

The above “fluctuating“ should be as described under “Check procedures“ in post #2 of my Lambda control thread. In your case (with the adjustment screw having been messed with) the Vp3 readings under conditions 4, 5 & 6 (warm engine running) may not be fluctuating at all. And if they are fluctuating, they will probably not be fluctuating around 50% of Vp6.

Whatever the two Vp6 readings and the six Vp3 readings will be, just report them.

And why are the other readings worthless? I am sure you've explained this but ...
As I said in post #80, these readings (4, 5 & 6) are in your case worthless with regard to their diagnostic value … because the Lambda adjustment screw has been messed with !

As explained in detail in my Lambda control thread, fiddling with the Lambda adjustment screw makes the ECU change the EHA‘s operating range by changing the EHA current … which changes the fluctuating duty cycle which, with the warm engine running, is a (easy to check) representative of the EHA current. … As I said in post #1 of my Lambda control thread, the duty cycle adjustment is actually an EHA current adjustment (and not a mixture adjustment, as commonly assumed ;)).

But turning the Lambda adjustment screw is not the only thing that changes the EHA current, respectively the duty cycle. Every fuel combustion affecting problem changes it too !

That is why I said in post #39 of my Lambda control thread:
Tampering with the Lambda adjustment screw without even checking or caring about the duty cycle (or the EHA current) is an even worse idea than simply readjusting a deviated duty cycle without caring about what‘s causing the deviation … with even higher risks for the engine’s health !
Plus, done without at least knowing exactly how far in which direction the adjustment screw has been turned, valuable diagnostic information is gone for good (!) and everything that has an effect on fuel combustion (see examples under “Please note“ in post #2) has to be checked first before further touching the adjustment screw, in order to reliably restore a proper condition of the system.“


... even though the adjustment tower has been fiddled with, you are saying that it is still a very valid diagnostic tool, but limited...?
The above listed duty cycle measurements 1, 2 & 3 (with ‘ignition on / engine off‘) and their static readings always provide valuable diagnostic information … no matter whether the adjustment tower has been fiddled with or not.

If the adjustment tower has been fiddled with, measurements 4, 5 & 6 (with the warm engine running) provide reliable diagnostic information only if the readings are static above 0% and below 100%. Fluctuating duty cycle readings under conditions 4, 5 & 6 provide reliable (and very valuable ;)) diagnostic information only if the Lambda adjustment screw, let alone the EHA adjustment screw, have not been unprofessionally fiddled with !

That is one of the reasons why I try to convince people not to fiddle around with that adjustment screw, depriving themselves of the most valuable diagnostic information they can get from their CIS-E cars … which is not limited to the injection system. … ;)

But, even with the adjustment screw having been messed with, these measurements (4, 5 & 6) still make some other sense. They might point to a possible & harmful exceedance of the Lambda adjustment limits, for instance, due to a too far cw or ccw turned adjustment screw ;) … which, among other things, a static duty cycle of ~ 0%, respectively ~ 100% might indicate.

I saw where you said the duty cycle should be run after changing out anything involved with the fuel system.
I said … for instance, in post #39 of my Lambda control thread … that the duty cycle should be readjusted (not “run“!) via adjustment screw as “the last thing to do after fixing all causes for its deviation“.

Run (as in “checked“) the duty cycle should be not only as one of the first things to do in case of engine issues, but also frequently, even if there is no obvious problem. … Sometimes I check the duty cycle (via ‘ashtray‘) when I‘m boredly waiting at a red traffic light … and sometimes I even monitor it during driving … while there are 30+ years old CIS-E cars it has never been properly checked on.

... can the duty cycle ever become valid once again for ALL measurements?
Yes it can … as you can deduce from the above quote from post #39 of my Lambda control thread. … First check and, if necessary, fix everything that has an effect on the fuel combustion. That includes things beyond the injection system, of course. After that has been thoroughly done, adjust the fluctuating duty cycle via adjustment tower while the warm engine is running at idle to a value close to 50% (EHA current fluctuating around zero mA). Then you have a proper basis for reliable complete future duty cycle tests again.

Once again H.D., kudos to you for taking your invaluable time to go through all of this.
Thanks Randtor. :) ... Last year I told an ex-colleage of mine that I‘m trying to explain the KE-Jetronic in a car forum. … His only reaction was: “Auwei!“ (“Oh dear!“) … LOL

H.D.
 

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Discussion Starter #85
Yes, as luckymike said: "WOW" ! ! ! !
H.D., your detailed explanation on "how to" (in this thread and others), reasons for doing the tests, and all responses to my questions are deeply appreciated. I'm sure by ANYONE who searches this (and other) threads attributed to you, I'm fairly certain you do not reside on this side of the pond(USA), but if you did I might have paid you a visit just to shake your hand and buy you a drink! I wish I had the knowledge to build that 'duty cycle instrument', and it appears luckymike is taking on that task. I will talk to a good friend of mine (electrical engineer) and find out if he might build one for me.
In the meantime, I plan on doing everything you have outlined before I purchase any more parts. I was going to buy an Idle Control Valve, but I'd rather wait on that and do the duty cycle test first, as you have strongly suggested the testing is still very valid and will provide a lot of info regardless of the control tower having been adjusted.
I will not be able to get to the testing procedure until the weekend, at the earliest, but no later than next week. I can use the time between to study the procedure more and get a good grasp on what I will need to do. Of course I will return to this thread and report results, and see where that leads me.
H.D. , I remain very grateful.....
 

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You‘re welcome Randtor.

I'm fairly certain you do not reside on this side of the pond(USA), but if you did I might have paid you a visit just to shake your hand and buy you a drink!
Haha … probably my English gives me away, right !? … I reside in Germany.

I wish I had the knowledge to build that 'duty cycle instrument' ...
With that instrument I can check a number of things, not only the duty cycle. It enables me to track down culprits within two or three minutes, which I sometimes see taking weeks or months in troubleshooting threads here at Benzworld. ;)

In the meantime, I plan on doing everything you have outlined before I purchase any more parts
(y) … I generally prefer testing & diagnosing over throwing parts at problems. Purchasing parts that do not replace culprits does not contribute to my enjoyment. ;)

I will not be able to get to the testing procedure until the weekend, at the earliest, but no later than next week. I can use the time between to study the procedure more and get a good grasp on what I will need to do.
Take your time Randtor … and don‘t think of the duty cycle test as being difficult. The most difficult part is the general dealing with a digital multimeter. For the two Vp6 measurements and the six Vp3 measurements just follow the procedures in post #83 ... and don‘t care about “pulling off the vacuum line between the throttle valve and the regeneration valve of the fuel evaporation system at the regeneration valve and blocking it“ this time.

H.D.
 

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Discussion Starter #87 (Edited)
Thanks H.D., I'm reasonably sure i understand everything in theory, but as they say, experience is the best teacher. Once I am "hands on" it may take me a while to do this (the first time!), but like everything, when it is done, it makes it more understandable and easier to do in the future.

In regards to your location, it was my assumption that since you were involved in MB engineering, you were likely German! Not your command of the english language, which is perfectly fine! Way better than what I could do in German! (I once took a course in college called 'Scientific German' - we translated scientific documents writen in the german language...All verbs piled at the end of sentences😳. I had previous courses in the german language but that course was incredible haha!).

In regards to your measuring device, I am in contact with my electrical engineer friend and he has done a preliminary overview. He already asked me some questions, but they are above my pay grade lol! If he has further questions would it be alright to post them here, or would you prefer I post them on this thread :
 

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‘Scientific German‘ … that‘s quite a challenge, also for most Germans. :)

In regards to your measuring device, I am in contact with my electrical engineer friend and he has done a preliminary overview. He already asked me some questions, but they are above my pay grade lol! If he has further questions would it be alright to post them here, or would you prefer I post them on this thread :
I actually prefer not to become too active in this forum before the technicians will have recovered the features that the forum had before August 20. Administrators told me they are working on it. … But questions regarding the test device you can post in that thread. I think that makes more sense than posting them here in this thread. You can also post questions about it via email, if you like.
 

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1985 500sel and 500sec 2012 E63 1989 Porsche 911
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can we duty cycle a CIS K system or is that just for the KE brethren
 

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can we duty cycle a CIS K system or is that just for the KE brethren
I don‘t know what you mean by “can we duty cycle“ and by “KE brethren“. I assume that by “CIS K system“ you mean the “K-Jetronic“. … This thread is about the KE-Jetronic, which is so different from the K-Jetronic that, in order to avoid unnecessary confusion, details about the former should, IMHO, not be discussed in a thread about the latter and vice versa. ;)
 

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Ok . Can u pm me your email. Thanks
 

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Discussion Starter #92
FYI for those following this discussion....
I have started a new thread which carries the proper title, the main theme in this thread... understanding and measuring the duty cycle. To continue following this conversation please see this thread:

 
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