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DIY videos-fuel system

13K views 39 replies 8 participants last post by  H.D. 
#1 ·
Lets see if this will work. If you have videos regarding repairs or information that will help diagnose problems with the fuel systems in the w126's, please add them below.
 
#13 ·
Changing fuel pump and check valve on 420SEL. The poster did not film the actual work but does a great job of explaining and pointing out the different part of the job. If you have to change your pump, this is a video you want to watch.
The vehicle was having difficulty starting and had to crank several times before it started.

 
#20 ·
It's nice to see people try to help others to maintain their CIS-E cars and I'm sure that the videos in this thread are posted with this laudable aim. I'm also sure that many viewers think that these videos hold professional information & advice. But having been involved as a young design engineer in Mercedes' CIS-E engines in the 1980's, I assure this forum that CIS-E related YouTube videos often hold incorrect information & inadvisable advice. ... Let me take the above video (from post 18) as an example:

At 3:33 the man in the video says:
The control pressure is the pressure that is fed through these 8 lines to the injectors“
^This is not correct. The “control pressure“ only exists in the lower chambers of the differential pressure valves and is not fed to the injectors. There is not even any hydraulic connection between the lower chambers and the injector lines.

3:48 and 42:35:
This is the idle mixture adjuster“ and This is the idle mixture adjustment...“
He uses ^these misleading names for the adjustment tower. The fact that the FSM department people simply adopted the name of that adjustment screw, namely “Gemischregulierschraube“ (mixture regulating screw) from the K-Jetronic manual in the KE-Jetronic manual doesn‘t make it less misleading. … On the KE-Jetronic, besides a short after-start & warm-up phase & WOT, the a/f mixture isn‘t even changed via this “adjuster“, unless the systems Lambda leaning or enriching limit (0% or 100% duty cycle) is exceeded, which is completely inadvisable, of course.

In my KE-Jetronic Lambda Control Thread I explained in detail what the actual purpose of this adjustment screw was & still is … (and when & when not to use it ;)).

10:35
The basis of this system is extremely simple“
In the past ~35 years I‘ve met a number of people who said ^this or something similar. It turned out that none of them actually understood this system. ;)

10:48
The fuel goes into this bottom chamber“
There is no such thing as the bottom chamber". The FD has as many “lower chambers“ & “upper chambers“ as the engine has cylinders and only a very small part of the fuel that enters the FD goes into the lower chambers.

27:50
If you have a car that is stumbling off the line… … you turn this screw in ¼ of a turn in“
^This should certainly not be done ! … If you have a car that is stumbling off the line, you should rather search for & fix the cause of that behavior, instead of masking it via this screw.

35:10
The pressure that is being fed to the system and the pressure that is being fed to the injectors should have a difference at idle of about 0.4 bar.“
^This is not correct. … “0.4 bar“ is the nominal pressure difference between SP (system pressure) and LCP (lower chamber pressure). And LCP is not the pressure that is being fed to the injectors. As I said above (at 3:33), there is not even any hydraulic connection between the lower chambers and the injectors.

36:05
The difference between the upper and lower chamber… …0.4 bar“
Again … 0.4 bar is the difference between SP (measured at the upper test port) and LCP (measured at the lower test port). The “upper chamber pressure“ can not even be measured at all. … For proper diagnosis it is important to know the role that the upper chamber pressure plays, though !

38:00
He suggests to “turn the EHA adjustment screw ¼ out, if that pressure difference is only 0.3 bar“.
What should be done first in the case he describes is to search for the cause of this smaller pressure difference, instead of masking it via EHA adjustment screw !

42:50
I‘m gonna make it really simple for you. Adjust the car to where it has the smoothest idle, the best starting and does not stumble off the line. That is a happy KE-Jetronic Mercedes.“
^This should definitely not be done ! … That would be a “KE-Jetronic Mercedes“ with (possibly many) problems masked via Lambda adjustment screw. ;) … The problems he mentions before & after that statement refer to causes that should be checked & fixed, instead of being masked via that adjustment screw ! … And don‘t let yourself be tricked into believing that you did the right thing, if after fiddling around with that adjustment screw the car behaves better ! … You just mask problems that way, with negative effects on the engine‘s health each time when Lambda control is not active. Plus you deprive yourself from a lot of valuable & revealing (yet widely ignored) diagnostic information that way.

46:40
That‘s why they call this the air/fuel ratio adjustment. They also call it the CO2 adjustment or idle mixture adjustment.“
They call it that, because they don‘t know what its actual purpose is. … ;)


I say ^these things not to criticize anybody but because they‘re important to know for quick & targeted CIS-E related diagnosis and proper maintenance … which, unfortunately, hardly takes place here at BenzWorld. And fiddling around with adjustment screws in order to make problems go away, instead of taking care of their causes is not what I call proper maintenance ! … Over here in ‘BenzCountry‘ that‘s called “Pfuscherei“ (botchery). ;)

I may be too short of time to respond to disagreements / questions. For more details I recommend to have a close look at CIS-E related posts of mine here in this forum (particularly in my KE-Jetronic Lambda Control Thread).

Anyway, I warmly recommend those who want to keep their “KE-Jetronic Mercedes“ in proper condition to beware of CIS-E related YouTube videos ! ... ;)

H.D.
 
#21 ·
HD,
Thank you for your input and the link to your thread. Any information that is helpful to fellow Benzworld members is certain to be appreciated. You obviously have an in depth knowledge in this particular area. As for "many viewers think that these videos hold professional information & advice", I cannot speak to the thoughts of others. I am sure Pierre considers himself (and rightfully so) a professional. If you are critical of the other videos posted in this thread, the goal was to support others in repairs they may be facing. You are welcome to add any videos that you find that contain more accurate information.
 
#23 ·
I am sure Pierre considers himself (and rightfully so) a professional.
I don‘t know ^this man, but … as someone in whose professional engineering life CIS-E engines played a significant role before their mass production started … I assure you that a lot of the man‘s info & advice in the videos in posts 12 & 18 is not only not professional, but plain wrong.

You are welcome to add any videos that you find that contain more accurate information.
Thanks Michael Pillay. … Maybe I'lI comment on the videos in post 12 when I have more time. For now I warmly recommend CIS-E car owners who place value on proper maintenance to bear in mind what I said in post 20. … I‘d like to post more, for quick & targeted diagnosis very helpful, info/advice here at BW that you‘ll most likely not find anywhere else on the internet. I just wish it would be better understood. ;)

BTW, in order to make a rough assessment of KE-Jetronic related info/advice on the internet, here‘s a hint: If it includes fiddling with adjustment screws, it is, with a probability bordering on certainty, not professional.

H.D.
 
#24 ·
BTW, with what I said in post 20, it should be self-evident that following the ‘advice‘ given in the video in post 17 is inadvisable too … (particularly see what I said in post 20 under ‘42:50‘ and ‘46:40‘).

The people in the videos in posts 17 & 18 impressively demonstrate how justified it was to press a difficult to remove anti-tamper plug into the Lambda adjustment tower of KE-Jetronic MBs before they left the factory. ;) … They don‘t seem to care about any of the things that should be considered before touching that adjustment screw and they don‘t seem to care about what it should be adjusted to either … if they are at all aware of those things.
 
#25 ·
HD
I appreciate all of the input and the corrections.
However, sometimes when I describe things in the KE system using incorrect details It is simply because they help the user understand the system a little bit more. For example, the fuel distributor is split in half into a top part of the bottom part. I know that in truth there is no bottom chamber but in the bottom of the fuel distributor there is a port for the fuel injection pressure gauge. I could probably use a better term like “bottom half” though.
Truthfully there are not a lot of people willing to step up to the plate and assist others who are struggling with these problems. I appreciate the assistance you’ve given people on this forum
I don’t have the benefit of factory training because I am from younger generation than you are. A lot of us had to figure out these things on our own.
I am not going to refrain from posting videos about the topic even if I get a few details incorrect. noticed that I was not post to videos on rebuilding fuel distributors because it is not a topic I am completely comfortable with.
If you ever have information that you think you can out to these videos to assist me my email is mbownersforlife@bellsouth.net
 
#26 ·
@Pierre Hedary, I actually stopped posting at BenzWorld (for reasons mentioned in This Thread). But I received an email notification about your post and since you talked to me in it, I post this reply.

I am not going to refrain from posting videos about the topic even if I get a few details incorrect.
What I commented on in post 20 are not only “incorrect details“. ;)

To counteract the, in general on the internet existing, abundance of incorrect information & unprofessional advice about the KE-Jetronic, one should at least refrain from so easily recommending to fiddle around with its adjustment screws. The reasons for their being hidden/sealed when CIS-E MB‘s left the factory were (and continue to be) a lot more justified than commonly understood.

If you ever have information that you think you can out to these videos to assist me my email is mbownersforlife@bellsouth.net
I‘m afraid I‘m too busy for that. Look for posts of mine here at BenzWorld. They hold a lot of KE-Jetronic related information, partly of which you‘ll most likely not find anywhere else on the internet … (including the reasons why those adjustment screws were hidden/sealed ;)).

H.D.
 
#28 ·
So what should I do? I have successfully helped a lot of people with basic KE adjustments. Should I delete all my videos?
or should I simply tell people I am not able to help them anymore?
I applaud you for your willingness to help others but I am unsure of whether you are trying to be condescending or not.
Many people from this forum have contacted me requesting help. I work with them personally as far as they want to go. I don’t know why they would contact me if all the answers are here. Regardless, now that I am more aware of my errors I can invite correction from you and other experts.
just so you know I would have loved to attend some kind of schooling on this topic if it were available . Perhaps you should host a zoom session for mbca so you can share all of your knowledge.
 
#31 ·
HD
I was formally educated about all of those hidden adjustments by Larry at CIs flowtech And ....
I have to say he did a great job.
I will continue to teach people based on my success with these adjustments because the results I have gotten have helped so many people.
these “sealed adjustments” are subjective.
I think they work best when you approach them with some knowledge and instruction but overall their adjustment should be a topic of discussion.
 
#32 · (Edited)
I was formally educated about all of those hidden adjustments by Larry at CIs flowtech ...
Whoever taught you what you say/recommend in your videos, he/she should read what I've posted about this injection system in this forum. ;)

I will continue to teach people based on my success with these adjustments because the results I have gotten have helped so many people.
I guess you will. … But I‘m sure that I could convince these people that it would be much better to fix the problems that are just masked by most of these adjustments, if they‘d see me show them in front of their eyes … (just to name one of the consequences).

... these “sealed adjustments” are subjective.
IMO, the term “subjective“ is not really suitable in case of logical systems (like the KE-Jetronic) … and it reminds me to the term “alternative facts“ that I heard certain, expertise rejecting, people use. ;)
 
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