[belstar2003]

Gentlemen,
Please rescue a fellow 107er. My 1980 450sl was running a bit rich and exhaust smelled like gas. I took the car to the shop and BMW mechanic suggested to adjust the air/fuel mixture by turning the screw all the way to the end and then 1.5 turns back. This was supposed to take care of the problem and adjust the mixture to the proper range. Well, I didn't do enough homework and haven't realized how sensitive that thing is. Sure enough it messed the whole freaking K-jetronic up because I never felt the limit point. The screw just kept turning.
Right now the car doesn't start, probably flooding the engine because it smells super rich. I don't know which way to turn the screw or how to get at least in the range where I can start and continue with adjustments. From what I understand you can only measure a duty cycle at pins 2 and 3 when the car is running. In my case I don't even know how to get it to start.
Any suggestions? Can I get away without getting a CO measuring tool, lambda meter and everything else or is there an easier way to figure this out? Any help is greatly appreciated.

 

[Djenka018]

If I remember correctly, service manual (egv107 sticky) shows default position

similar to this (image from M110 280 engine manual):

 

[ctaylor738]

Right is rich, left is lean, meaning that if you are looking down at the fuel distributor, you turn clock-wise to go rich.

Suggest you try to re-trace your steps, and try to reverse what you did before, going maybe 1/4 turn at a time.

From your description, you probably went way too lean.

Once you get it running, you need to either find someone who can set the mixture properly, or learn to do it yourself. You can use a something as simple as a volt meter to measure the voltage between pin 3 and ground and adjust the mixture to 50% of battery voltage.

 

[rollin560]

turn key on to build fuel press. then turn screw counter clockwise while checking for free play in center round plate. turn screw until there is about 1/8" to 1/4" play then try to start car. after starting adjust to best running position. this should be less than 1 turn. that should get back to basic so it will run. after it is fully warmed up adjust again. proper way would be to use a co meter but best running position works good.:smile

 

[Clarkz71]

From what I understand you can only measure a duty cycle at pins 2 and 3 when the car is running.
In my case I don't even know how to get it to start.

Once you get the car running, (the method above "should" work) you
can set the mixture at the X/11 9 pin port, it is pins 2 & 3 as you said.

This can be done with a simple volt meter, or Sears and other stores sell
digital multi meters that have a duty cycle feature and will read %.

The reading should oscillate around 50% at operating temp (closed loop)
and be at 50% fixed on a cold start when the system is in open loop.

If using a simple volt meter, it should be 50% of running voltage.

If running battery voltage is say, 14 volts. 7 volts would be 50%


.

 

[belstar2003]

Thank you guys. Your advises really helped. When I was turning the AF screw, the control flap wasn't moving. Instead, it only moved by about 1 mm, and when I manually depressed it-it went all the way back up. After reading your comments and confirming that the flap should actually be moving with the screw adjustment, it narrowed my focus on the screw itself. I tried to look inside the CIS by depressing the flap and using a flash light and an inspection mirror, but couldn't see the screw. My heart dropped and I was almost sure that I turned it by so much, that the screw became loose and was floating somewhere inside the CIS. Took my little magnet, tried to snake it- no results. At that point I was so angry at myself, the CIS and the damn mechanic who gave me a bad advise, that I decided to go ahead and take the whole thing apart.
It took about 30 min to remove the whole injection system out and another 30 min to figure out what the problem was. The top allen type screw that should be pressed against the lower one inside the CIS got stripped. All it was doing is just spinning inside without actually making any adjustments. I had to drill out one of the dead clips that hold that little bracket in place to remove the screw/spring assembly from the system.
Will be working on fixing this pin tomorrow. Either will cut a small piece of 3mm allen and weld it to assembly or will completely remove the pin out and put a sealed removable cap on top. It can still be adjusted by a long neck allen if I want to.
After I put everything back together I'll proceed with suggested adjustments.
Again, thank you all for great comments.

 

[rowdie]

Please fill in your profile with location and vehicle.
If you are in the US and using a PC you can subscribe to the EPC. It is free and link is in the EGv107.

 

[belstar2003]

Done!

 

[rowdie]

Thanks
Checked the EPC and it appears there is a kit to replace the parts inside that tower. Part number 000 070 08 18. Not exactly cheap. Mercedes-Benz Parts - OE Discount Parts Free shipping. I also checked and mine out of an '84 is different number

 

[Myndex]

Once you get the car running, (the method above "should" work) you
can set the mixture at the X/11 9 pin port, it is pins 2 & 3 as you said.

This can be done with a simple volt meter, or Sears and other stores sell
digital multi meters that have a duty cycle feature and will read %.

The reading should oscillate around 50% at operating temp (closed loop)
and be at 50% fixed on a cold start when the system is in open loop.
.

On 1980 through 1985 cars, you can NOT use a regular duty cycle meter at pin three of the diagnostics connector.

80-85 use a frequency valve which is simply a modified electric fuel injector – as a result, the waveform needed to drive the frequency valve is sufficiently complex that a duty cycle meter will not work.

To use a regular duty cycle meter you need to do my you see you modification to hook up to pin the 17 of the ECU.

Here is a link for the modification: http://www.benzworld.org/forums/r-c107-sl-slc-class/2189370-1980-1985-ecu-mod-correct-duty.html

Here is a link for adjusting mixture for 80 through 85 cars http://www.benzworld.org/forums/r-c...25-k-jetronic-lambda-overview-adjustment.html

And here is a link that describes the internals of the ECU in more detail: http://www.benzworld.org/forums/r-c107-sl-slc-class/2180857-inside-ecm.html

And finally here's a link for the modification to strap the O2 sensor to chassis: http://www.benzworld.org/forums/r-c...58-oxygen-sensor-mod-single-wire-sensors.html

 

[Clarkz71]

This is the meter we used on ALL CIS and CIS-E cars 1980-1993

The plug had 2 pins, they engadged pins 2 and 3 of X/11

Back in the day I used this meter and then my Fluke 88 on the "frequency setting"

The valve you call "injector like" is called a "frequency valve".

My meter read the same percent as the Bosch meter.

Been there, done that. Don't know why you had an issue.

Maybe you need a Fluke and not just any DMM, can't say, but other members
on the forum have used a Sears meter with duty cyle on the 126 forum.


The dealer tool, look close it has a voltage scale and percent scale.

 

[Clarkz71]

And from my Fluke 88 maunual, you'll note it says "K JETRONIC"

Not KE.

 

[Djenka018]

And from my Fluke 88 maunual, you'll note it says "K JETRONIC"

Not KE.

Mercedes EHA adjustment (KE-Jet) and they use, well, Fluke 88.

 

[Clarkz71]

Yes, like the original Bosch lambda meter, the Fluke will do both.

I just wanted to point out it does do the pre 1986 cars.

 

[Myndex]

This is the meter we used on ALL CIS and CIS-E cars 1980-1993

The plug had 2 pins, they engadged pins 2 and 3 of X/11

Back in the day I used this meter and then my Fluke 88 on the "frequency setting"

Yes, the Bosch meter is made to specifically parse the complex waveform used on 80 to 85 cars with a frequency valve. As far as the fluke 88, that is a specific meter for automotive use. Perhaps it's duty cycle setting has a low pass filter to ignore the PWM of the signal in question.

I used FOUR different "regular" duty cycle meters and found that none of them would correctly report the duty cycle of the complex waveform. This prompted my extensive research last fall and the several threads that I wrote on the subject for correct mixture adjustment.

http://www.benzworld.org/forums/r-c...25-k-jetronic-lambda-overview-adjustment.html

The valve you call "injector like" is called a "frequency valve".

I know that. The frequency valve IS a repurposed fuel injector. Instead of spraying into the cylinder, the output is connected to a hose which then directed back to the fuel tank return in a similar way to the WUR. The input of the frequency valve is from the lower chambers of the fuel distributor so that it affects the differential pressure of the lower chamber.

My meter read the same percent as the Bosch meter.

Been there, done that. Don't know why you had an issue.

Maybe you need a Fluke and not just any DMM, can't say, but other members
on the forum have used a Sears meter with duty cyle on the 126 forum.

I've tried four different brands of duty cycle meter, and all of them reported an incorrect duty cycle on pin three – and this is because the waveform is too complex for a "regular" duty cycle meter.

The fluke 88 may be able to read it correctly, as it is dedicated to automotive use perhaps it has a low pass filter in it. But that's not true of most duty cycle meters.

If you look at any of the threads that I've written on the subject last fall including the one I link above you'll see that the waveform shown on oscilloscope is complex due to the PWM portion of the signal that is sent to the frequency valve.

I demonstrated this to a few of the folks here at the get together yesterday in LA when I brought my oscilloscope help out Nick with his 380 SL.

It is bad advice to tell people that they can use a standard duty cycle meter on pin three for 80-85 cars. It is not the case. I was quite frustrated with this last fall when I was working on my car as that was the advice that I had read several times here and on some other forms. The advice is incorrect, and after extensive research I wrote those threads to provide correct information.

You need a meter which can completely ignore the PWM portion of the signal. If the fluke 88 does that, fine. However most duty cycle meters do not ignore the PWM portion, and therefore you will not be able to make an accurate adjustment using that duty cycle meter.

Pin 17 of the Bosch ECU does have a nice square wave for test purposes that represents the duty cycle of the frequency valve. VW and some other car manufacturers bring been 17 out to the diagnostic plug for correctly setting mixture with a standard duty cycle meter. However Mercedes does not. For Mercedes you either need to use the Bosch tool, an oscilloscope, or do the mod to bring pen 17 out as i show in this post: http://www.benzworld.org/forums/r-c107-sl-slc-class/2189370-1980-1985-ecu-mod-correct-duty.html

Since I haven't personally used the fluke 88, I cannot tell you how accurate it is in terms of ignoring the PWM portion of the signal. I CAN tell you that other duty cycle meters do NOT work.

The KE – jetronic uses and EHA valve, and that is driven with a simple square wave so it is possible to read a KE jet using a simple duty cycle meter. It's useful to note that to use the Bosch tool on KE jet, that you must set it to the IR setting. The Bosch tool has circuitry to correctly read pin three of the diagnostics connector for a Kjet. Most duty cycle meters do not.

 

[Myndex]

And from my Fluke 88 maunual, you'll note it says "K JETRONIC"

The fluke 88 manual I downloaded does not have that indication. Regardless, it's possible that the fluke 88, being for automotive use, has the appropriate circuitry to ignore the PWM portion of the signal sent the frequency valve.

But this is not true of most duty cycle meters.

If there's one specifically made by Sears, I'd like to know what the exact model number is, and I'll go pick one up and see how well it works compared to the other methods which I have related in several lengthy threads on the subject here at Benzworld.

 

[Clarkz71]

I've tried four different brands of duty cycle meter, and all of them reported an incorrect duty cycle on pin three – and this is because the waveform is too complex for a "regular" duty cycle meter.

The fluke 88 may be able to read it correctly, as it is dedicated to automotive use perhaps it has a low pass filter in it. But that's not true of most duty cycle meters.

The Fluke 88 is a $400 meter, not surprised a $40-50 meter doesn't work.

Regarding advice, everybody who works on their own car need a good
digital multi meter in any case.

The fluke 88 manual I downloaded does not have that indication. Regardless, it's possible that the fluke 88, being for automotive use, has the appropriate circuitry to ignore the PWM portion of the signal sent the frequency valve.

But this is not true of most duty cycle meters.

If there's one specifically made by Sears, I'd like to know what the exact model number is, and I'll go pick one up and see how well it works compared to the other methods which I have related in several lengthy threads on the subject here at Benzworld.

Not just possible, it does. Also checks EFI injector duration time

The page I posted is right out of my 1993 Fluke 88 manual

Clearly, K Jetronic frequency valve is covered.

Also, those of you that remember the points ignition days and have
an analog dwell meter. That will work for Lambda on 81-85

 

[Djenka018]

The Fluke 88 is a $400 meter, not surprised a $40-50 meter doesn't work.

Regarding advice, everybody who works on their own car need a good
digital multi meter in any case.




Not just possible, it does. Also checks EFI injector duration time

The page I posted is right out of my 1993 Fluke 88 manual

Clearly, K Jetronic frequency valve is covered.

Also, those of you that remember the points ignition days and have
an analog dwell meter. That will work for Lambda on 81-85

No reason for cheaper multimeters not to work. The difference is mostly in accuracy, in 99% cases. Fluke 88 has positive or negative threshold trigger selector. When you get a chance, try to see the difference this makes. On an el cheapo multimeter with % reading it could be as simple as reversing the probes (reverse input signal polarity).

 

[Clarkz71]

No reason for cheaper multimeters not to work. The difference is mostly in accuracy, in 99% cases. Fluke 88 has positive or negative threshold trigger selector. When you get a chance, try to see the difference this makes. On an el cheapo multimeter with % reading it could be as simple as reversing the probes (reverse input signal polarity).

I agree, and I have heard about reversing the leads from other members.

The Fluke is over 20 years old, I find it difficult to believe current meters don't work.

I'll try that trigger selection test

 

[Clarkz71]

Something else that is not understood by some.

Regardless if CIS, CIS-E or LH like my M119.

Lambda is a reading of the o2 sensor and what signal the lambda control
unit is sending the frequency valve to maintain a 14.7:1 fuel mixture.

Unplug the o2 sensor and you'll see a fixed 50% on a hot engine.

On my LH Jetronic the LH control module does it. Yes, I have a lambda
reading on a 93 EFI car.

Reading is 50% just like your CIS cars


From the 1980 Model introduction FSM