When testing the Duty cycle, why do I get 50% when koeo - PeachParts Mercedes-Benz Forum

90MB4matic · #1 01-02-2010, 02:07 PM

Accorcding to the manual i should be getting 70% is 50 considered a fault in the system and that why it does not show 70?

junqueyardjim · #2 01-02-2010, 02:11 PM

Are you asking or telling?

90MB4matic · #3 01-02-2010, 07:03 PM

Asking only thing i am explaining is that it is suppose to be 70 and i want to know why its not

anziani · #4 01-03-2010, 12:13 PM

I give up. What is he talking about? And what model car?
Anziani
'93 300CE 181K
'95 E420118K

junqueyardjim · #5 01-03-2010, 12:15 PM

I think he is still celebrating New Years Day - and he doesn't want to quit

90MB4matic · #6 01-03-2010, 12:32 PM

Ok let me explain further for u, When testing the Duty cycle of my
90 MB 300E 4matic the inital test (static test) before you start playing with the adjustment is to turn the key on and read the duty cycle. The value according to the manual is 70% or 4 volts, the process is highlighted in the website http://landiss.com/mixture.htm, the info i am referring to is
Static tests
It is suggested that before the active (engine-running) tests are attempted, some static tests should be performed to check a few of the basic components of the Bosch fuel injection controller.
With the ignition on but the engine not running, the duty cycle tells which version of controller is installed. A 70% duty cycle indicates the standard controller with the ability to read some faults by monitoring the duty cycle. 85% indicates the California controller, which ordinarily displays the faults as a blinking LED on connector X92, although it can be programmed to display the faults as an X11-pin3 duty cycle. 100% indicates the controller does not display fault codes in this manner, or is faulty.
Assuming the "standard" 49-state controller (70% duty cycle with ignition on but engine not running, or about 4 volts average), the following tests should be performed before attempting to adjust the idle mixture.
1) Idle Contact: Deflect the air flow sensor plate. The duty cycle should decrease to 10%. If it remains at 70% test the throttle valve switch (Job 07.3-121).

2) Full Load Contact: Open the throttle completely. The duty cycle should decrease to 20%. If it only decreases to 40% test the air flow sensor potentiometer (Job 07.3-121).

So basically what i am asking is that when i turn the ignition ON it does not read 70% it reads 50% WHY IS THAT?

dhjenkins · #7 01-04-2010, 01:35 PM

Quote:

Originally Posted by 90MB4matic

Accorcding to the manual i should be getting 70% is 50 considered a fault in the system and that why it does not show 70?

Yes.

90MB4matic · #8 01-04-2010, 03:49 PM

I rather no one answer then get comments about nothing and have a post full of information no one needs, in that case i would erase the post so its not there wasting space. Next time ask for a better explanation instead of a comment, and your yes is a yes to stop me from posting or you actually know for a fact that it is a fault and know what is? Or should i stick with what i think and consider that to be a fault and 50% is considered to be a problem with the O2 Sensor

rayhennig · #9 01-05-2010, 02:21 AM

You're asking about setting duty cycle for the Bosch KE Jetronic. The basic rules apply to most early 90s Mercs, 24 valve included.

I'm busy right now so can't respond at length. I've measured 50% like you, followed by 50% +/- 3% when idling. The car runs fine but a year ago I saw the 75% that you mention (engine off). Don't know what's changed.

Keep searching as this has been covered at length elsewhere for 190s, W126s, W124s etc. etc.

Bon courage.

RayH

JamesDean · #10 01-05-2010, 06:55 AM

I was unable to locate, in the factory service manual that I have, anywhere that it specifically stated 70% Federal, 85% Cali when key on, engine off...thats not to say that I disagree or do not believe the information on the website..

Ensure that you have your probes for the meter in the correct places: +pin3, -pin2 of x11 connector on fender of car...and then retest the voltage..

Ensure that you are using the formula properly:
Duty Cycle = [1 - (V{pin 3}/V{max})] x 100%

I did a fair amount of work on this topic, here is some information on it, you might find something helpful in there...
http://www.peachparts.com/shopforum/showthread.php?t=253393

Ignoring the not reading 70%, have you checked your duty cycle with car running @ operational temp?

If you do this and get a 50% then its certainly the O2 sensor. Alternatively you could disconnect the O2 sensor with the car at operating temp and check its output voltage, its should be oscillating rapidly. If it is a fixed value, time for replacement.

Here is the chart for errors generated during that and courses of action to fix problem:

http://i98.photobucket.com/albums/l250/MafiaNicky/50006pdf2.png

Hope this helps...

90MB4matic · #11 01-05-2010, 02:48 PM

Its defenitly 70% with key on for the past 4 years it has been the same thing then all of sudden the car seemed to act irregular so i changed the fuel filter after checking the fuel pressure and that seemed to correct the problem. I did also however clear the codes and system of faults but the 50% came up ever since then. I checked the O2 sensor the other day and decided to clean the sensor by means of a torch to remove the carbon build up and test it that removed the 50% fault and now i have a 30% with key on so i am chasing the ECT as the fault. The duty cycle is between 45%,50%,55% it seems to be changing a bit too much for past years its been in the 45 50 region, It seems to me that the cart is running a bit rich as it is so i will be testing the ECT today to see if there is a problem with it as well as the EHA valve since it is influenced by the coolant temp sensor. Oh and i have also have a code 29 which refers to the cfi and ezl seeing different temps.

tinypanzer · #12 01-05-2010, 08:48 PM

Welcome to the forum. This is one of the best and most knowledgeable MB forums out there.

Once you start posting and contributing here, you will find that quite often there are somewhat belligerent and short tempered people who show up, post one question (usually very badly worded) and then proceed to poo-poo whatever advice they have been given. Perhaps you were mistaken for one of these types of users, and thus the response you got was not shall we say, all that helpful.

However, one must remember that the etiquette and demeanor of the folks on a given discussion board is just as unknown to a new user as the user is to the folks on the board.

I think perhaps you took just a bit too much offense at the off-hand comments made by one of our own who apparently was just having a bit of fun and not say, insulting your gene pool. Was there a more polite way to point out that you didn't word your question in a way that would lend itself to being answered? Sure. But then again, you're the one asking for help here, and you're also the new guy. One can hardly justifiably complain about the comportment of someone responding to a request for free advice, now can one? What do I know, I'm not a forum moderator.

At any rate, all of us who seek advice must occasionally remind ourselves of the old adage pertaining to honey and vinegar.

Good luck and welcome to the forum.

Quote:

Originally Posted by 90MB4matic

I rather no one answer then get comments about nothing and have a post full of information no one needs, in that case i would erase the post so its not there wasting space. Next time ask for a better explanation instead of a comment, and your yes is a yes to stop me from posting or you actually know for a fact that it is a fault and know what is? Or should i stick with what i think and consider that to be a fault and 50% is considered to be a problem with the O2 Sensor

brewtoo · #13 01-05-2010, 11:43 PM

I apologize for the sarcastic responses above. The responders took the position that the original poster did not know what he was talking about, when in fact he was the only one who did know what he was talking about.

r0nd3L · #14 05-30-2010, 06:03 PM

Did you ever resolve this problem?

My recently purchased 300E runs excellent with one exception. It sometimes stalls right after starting or stumbles for few seconds until idle stabilizes.

I checked the duty cycle from X11 connector and here are the results:

Ignition On, Engine Off: 50%
Engine at Idle: 48%-54%
Engine at 2,500RPM: 68%-72%

What would cause it to be 50% and not 70% with engine not running?

ps2cho · #15 05-30-2010, 07:48 PM

Quote:

Originally Posted by r0nd3L

Did you ever resolve this problem?

My recently purchased 300E runs excellent with one exception. It sometimes stalls right after starting or stumbles for few seconds until idle stabilizes.

I checked the duty cycle from X11 connector and here are the results:

Ignition On, Engine Off: 50%
Engine at Idle: 48%-54%
Engine at 2,500RPM: 68%-72%

What would cause it to be 50% and not 70% with engine not running?

Have you replaced your OVP?