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1986 560SEL
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Discussion Starter #41
With a 30yr old FD there is more than a 50% chance that it is not in spec (tiny splits in diapghram - deteriorated o-rings causing blockages in very fine capillary tubes etc etc) and i suppose before jumping into a rebuild i feel the DIY home test with the vials/glass jars to accurately measure flow from each injector line is a good start
So, I'm not sure where I am supposed to start...and finish... can you please specify what I am looking for and what I should do?

The other main issue is a vacuum leak somewhere and requires a smoke test before you do anything else with the tune-up
OK, I guess I will build that smoke test DIY I saw on YouTube!

And most important Injectors that are not spraying an even fine mist when they open (even new injectors requre bench testing before are swapped in) and injector seals that have gone hard with age and not 100% sealing.
I was not the least surpised when testing some of my injectors i have pulled and bench tested in the past - that they were not up to spec and spraying correctly
OK, so I should pull the injectors and bench test? I am not sure how to do any of that, but I am willing to learn, if provided direction.

Doing a test on the POT upfront I would also consider essential (an easy test to perform) to eliminate any worn tracks as an issue.
And what is the 'POT'? (Not a drug test, right?!?!:ROFLMAO:) ......Thanks!
 

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Discussion Starter #42
H.D., I certainly can see now how the duty cycle can provide invaluable information. Even with the car running great, I assume something (or many somethings) are still not right, basedon my duty cycle numbers. Given the suggestions provided by KRH, would you agree that is where the next phase of my work should be? ...Thanks!
 

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1990 420 SEC
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The pot would be AFM potentiometer. On your car it probably is ok as car now seem to work ok. MMWA has couple of YouTube videos on that .
 

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87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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I have one of those Kent Bergsma (Mercedes Source.com) injector testers he sells
But you can make your own for very little cost if you have an air compressor/adjustable pressure gauge/ length of hose to fill with fluid and one end that clamps onto the injector

The Potentiometer (POT) that measures the air-plate arm movement can be easily tested on the car without by just removing the air-cleaner housing
On the Car -

Plenty of Vids on smoke testing a CIS engine
 

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1986 560SEL
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Discussion Starter #46
Thanks gents.
KRH I watched the videos you provided, thank you. There is good info there that should help me drill down into the problem more. I will likely do the vacuum leak smoke test first, then take the next step, checking the spray pattern for the injectors.
Heikkif, thank you also for providing some answers as well.
H.D., my thanks once again. In going back and reading your multiple posts and suggestions, I continue to have more insight. Some of the things you recommended a few weeks ago got put aside because at the time I had no idea what they meant or how to do them. Now, after more experience, and understanding the importance of the tests, I am going to go back and complete all the recommended diagnostic steps I pushed aside before.
It will be some time before I can do all this, Thanksgiving is upon us and I will not have as much time to work on the car. And, I will need to build a simple smoke test device to do that part. I was hoping to have the car up and running well before winter sets in. I don't want to drive the car in snowy weather, so I might be putting it up for the winter soon, and working sporadically in the cold weather to straighten it out, when I can catch some nicer, warmer days.
Thanks again!
 

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1988 300CE
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H.D., my thanks once again. In going back and reading your multiple posts and suggestions, I continue to have more insight. Some of the things you recommended a few weeks ago got put aside because at the time I had no idea what they meant or how to do them. Now, after more experience, and understanding the importance of the tests, I am going to go back and complete all the recommended diagnostic steps I pushed aside before.
It will be some time before I can do all this, Thanksgiving is upon us and I will not have as much time to work on the car. And, I will need to build a simple smoke test device to do that part. I was hoping to have the car up and running well before winter sets in. I don't want to drive the car in snowy weather, so I might be putting it up for the winter soon, and working sporadically in the cold weather to straighten it out, when I can catch some nicer, warmer days.
Thanks again!
You‘re welcome! … Take your time, Rand … and postpone these things until after the winter, if you like.

Now (after the o2 sensor replacement & the temporary duty cycle readjustment via adjustment screw) your car‘s condition is more or less the same as before the 'hesitation/stumble‘ started. The current duty cycle readings show that there is still a problem / are still problems that is/are masked by the current adjustment screw setting … like it was the case already before you bought the car. But don‘t feel too bad about that. Considering that most CIS-E cars that are driven out there have problems that are masked by unprofessional settings of the Lambda adjustment screw, there‘s nothing to worry about putting the car in its current condition up for the winter.

Now that we know that the o2 sensor itself was the culprit of the 'hesitation/stumble‘ (and not its missing connection to ground via exhaust pipe or the ECU‘s processing of its signal), the resistance measurement between o2 sensor & ground and the simultaneous o2 sensor voltage / EHA current / LCP tests are not necessary anymore at this point. What would make the most sense at this point is a check for ‘arteriosclerosis‘ in the upper part of (some of) the FD's metering slits, which I mentioned in post #38 and a check for proper spray patterns of the injectors.

The best way to check these things is a fuel volume flow comparison test (done, for instance, with glass jars, as KRH mentioned in post #39) at different positions of the CP … once without injectors & once with injectors. That will show how equal the flow rates are through the injector ports at the FD and through the injectors and how equal & good the injector‘s spray patterns are.

If you want to do this yourself properly, it requires quite a bit of preparation. In that case I recommend to build a test assembly like this:

2612302


You need:
  • 8 equal glass jars
  • a few (~500 mm long) wooden boards
  • 4 threaded rods and a few nuts & washers
  • 8 (300-400 mm long) fuel & pressure resistant hoses (part 4)
  • 16 hose clamps (part 5)
  • 8 injector pipes (for instance, from a junk yard)
Cut off both (~50 mm long) ends of the injector pipes (parts 1 & 2 in the drawing) and thoroughly deburr & clean them.

For the test remove your car‘s injector pipes from the FD and connect each part 1 to the FD. Then do the test with the FPR (Fuel Pump Relay) removed and FPR sockets 7 & 8 jumpered and the AFM plate deflected to several positions … once without injectors connected … once with injectors connected to part 2 at the other end of the hoses.

Happy Thanksgiving! :)

H.D.
 

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1986 560SEL
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Discussion Starter #48
H.D., thank you for this! Wow, you are really drilling down and explaining so well, and for me that's great. As mentioned I am a real novice when it comes to these systems, and most any electrical stuff with cars. You are correct in that the car is running as well as it was when I purchased it just under a year ago. I bought it as a surprise for my wife (who always wanted a Mercedes), and I fully expected to do some minor repairs, but I had no idea I was going to involved in something as complicated as this. However, as you proved, it appears to be difficult to do these tests, but when I did the duty cycle measurements, it turned out to be an easier job than I thought it would be. I also grew to understand what this all meant!

My biggest disappointment to date is that I have been working on the car so much, my wife has not had a chance to use it much. Now, come to find out she is not comfortable with it because it is such a big car. She feels like she can't drive or park it properly, and is so worried that she is going to bang it up. I'm hoping she will give it a go more frequently after I get it squared away. She thinks she is going to break down somewhere and be in a big mess if that happens. Fingers crossed!

Your drawing and instructions are spot on. it took a while to figure out what I needed to do, but in conjunction with the videos provided, I get it. It seems like I will be testing the injectors for proper function and spray pattern, as well as testing the openings in the FD fo make sure they are all patent and 'arteriosclerosis' has not set in! Please correct me if I am wrong.

I hope to get to this over the next few weeks, but if time becomes an issue it will have to wait until early January, after the holiday season is over, and when I get some warmer days so I can work in the garage. I live an hour south of Boston, and though we don't get huge quantities of snow, we sometimes get pretty good storms. And, it can be pretty cold trying to work in an unheated garage during the winter months. I have done so on occasion, as I have 3 old Triumphs I work on, at a leisurely pace. But I have to pick my days.

Thank you for the Thanksgiving good wishes! I am full of turkey, stuffing and dessert! All of our large family group (16 peeps!) has gone home so I had a chance to sit and write this up, while my wife tries to recover lol!

And thank you to all of those that have contributed information and comments. I would never have been able to do the work on this car without all of your invaluable input. As Arnold Schwarzenegger said: " I'll be back "... ;)
 

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87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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Just to add to this thread on the testing of the FD calibaration & injector flow - (half the battle of getting good idle & performance & economy)
This is for a Gen1 set up on a test bench but it is very detailed and informative - filmed over two video's
Enjoy
 

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1990 420 SEC
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On part 3 of the videos posted by KHR one can see what happens when fuel pump does not have enough of capacity to maintain fuel pressure or something else is restricting the flow..
 

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1986 560SEL
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Discussion Starter #51
That video series is very helpful, thank you KRH. It puts into motion what H.D. has been voicing and drawing out. The fellow doing the work on the video really explains things well, and everything he is talking about was very understandable to me since digesting what H.D. wrote up and hi-lighted several times. Wow, what an education!

I am on my third tank of gas mixed with Sea Foam, as my mechanic friend suggested a while ago that the injectors were likely a big part of my issues. In fact he found 2 that were not functioning as expected when I was with him. He loosened the nut holding the pipes going to the injectors on the FD, and 2 of the 8 hardly wept fuel. He did manage to work on them for a few minutes and got it sorted, but suggested I run at least 3 tankfuls of Sea Foam and get out on the highway at top speeds, intermittently, to run the sea foam through the injectors and clean them up. I think that has helped, but it may be necessary to really take them out and test/clean appropriately, and replace seals/o-rings as necessary.

I had a very primitive understanding of it all, but now I am much better informed and I think I can do everything - slowly! - that I have been shown. As I mentioned before, I can do the work if directed what to do and where to go. My downfall is that I want to understand what I am doing and why, as well!

Thanks again to all. I look forward to getting the work done. Right now I have a head cold and a persistent cough that won't quit. My lovely wife has barred me from the garage seeing as how it's hovering around 34F here today! (I am 1 hour south of Boston, Massachusetts) And we are expecting a snow/rain storm here for the next few days with temps about the same. Cheers all!
 

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Just to add to this thread on the testing of the FD calibaration & injector flow - (half the battle of getting good idle & performance & economy)
This is for a Gen1 set up on a test bench but it is very detailed and informative - flimed over two video's
These videos do show a similar set-up with measuring cylinders instead of glas jars. Glas jars, with their bigger diameter, enable you to check the injector‘s spray patterns much better, though.

I‘m sure you know this, KRH … but furthermore I want to point out to the OP (and other readers) that the K-Jetronic in these videos and the KE-Jetronic in the OP‘s car are two very different systems. A lot of what‘s said & shown in these videos does not apply to the KE-Jetronic.

BTW, the tests that I suggest in post 47 (as well as what‘s shown in the videos) are not “FD calibration“ tests. They‘re just “flow comparison & spray pattern tests“.

As far as the FD goes, the part of my tests without the injectors installed mainly provides insight regarding the condition of the metering slits (and o-rings). After that is done, the part of my tests with the injectors installed provides info regarding the injector‘s flow rates & spray patterns. … The tests in the video (all done solely with injectors installed) don‘t really provide (reliable) info about any of these things.

... it appears to be difficult to do these tests, but when I did the duty cycle measurements, it turned out to be an easier job than I thought it would be. I also grew to understand what this all meant!
Right! … (y)

When I first came across Benzworld I was surprised to see how rarely the duty cycle check was suggested in this forum. And the few times I saw members suggest it they suggested to simply readjust it if it was out of line. They didn‘t seem to know that the duty cycle constitutes valuable diagnostic information that should not be erased that way, but taken as suggestion what to check next. That was one of the reasons for the Lambda Control Thread I started ~3 years ago. Unfortunately, the duty cycle check is still hardly suggested/done and correctly acted upon here at Benzworld.

Maybe this thread of yours helps a little in this regard. The duty cycle check, as described in post #39 in my Lambda Control Thread, is the first, and usually most informative, step of systematic testing/diagnosis in case of faulty running behavior of CIS-E engines. It‘s done in less than 5 minutes and can save a lot of time & money on troubleshooting.

My biggest disappointment to date is that I have been working on the car so much, my wife has not had a chance to use it much. Now, come to find out she is not comfortable with it because it is such a big car. She feels like she can't drive or park it properly, and is so worried that she is going to bang it up.
Your wife would probably fall in love with my wife‘s 300CE on her first trial run. :)

Get well soon! … and wait with these tests until next year when it gets warm again. :)

H.D.
 

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Sorry i missed the 3rd vid being posted up but have now added it in and yes this is a demo in the gen1 K-Jet system (KE-Jet does is a more advanced system) but it still demonstrates that if a FD is not functioing correctly - no matter what else you do with adjustments to Duty cycle you can't get the engine in spec.
And Yes as HD mentions there are two tests that can be done checking flow (without injectors connected to purely check the FD flow to each injector line and with injectors connected to check the injector performance)
Sorry this is digressing away for a fews posts on the intitial topic of duty cycle checking and adjustment - but thought it necessary we cover off on Vac leaks/fuel system issues before starting on DC.
also one last equation that can adversely affect engine performance is an old clogged up original CAT that has been on the car for many years and is way past it use-by date and causing adverse back-pressure which causes all sorts of issues and poor performance
 

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Discussion Starter #54
KRH, thank you, I did see Video #3 as it came up after #2 automatically on youtube. No apology necessary - your information provided is certainly important to recognize and act upon. IMHO it does not wander away from DC checking, but adds TO it. Vacuum leaks were mentioned by H.D. very early on, and knowing about a blocked CAT is also a potentially important piece of the puzzle. Thanks for your input!

H.D., or anyone, can you clarify from post #47:
For the test remove your car‘s injector pipes from the FD and connect each part 1 to the FD. Then do the test with the FPR (Fuel Pump Relay) removed and FPR sockets 7 & 8 jumpered and the AFM plate deflected to several positions … once without injectors connected … once with injectors connected to part 2 at the other end of the hoses.

How do I 'remove' the FPR ( I assume I have to unplug something?), and where are the 'sockets 7 & 8 located? (again, I assume they will be evident as part of the plug that I have to disconnect??). Sorry, as mentioned, I am really 'green' when it comes to this system!
 

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Fuel pump relay is a black box at front of steering wheel between fire walls. Search forum for fuel pump relay. You just have to pull the relay upwards until it comes out. Do not be afraid or surprised if the case of relay comes off first.
 

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... yes this is a demo in the gen1 K-Jet system (KE-Jet does is a more advanced system) but it still demonstrates that if a FD is not functioing correctly - no matter what else you do with adjustments to Duty cycle you can't get the engine in spec.
CIS-E engines will never be in spec as long as there is a problem with any component that has an affect on the fuel combustion (not only the FD) ... no matter how well duty cycle adjustments via Lambda adjustment screw (or via EHA adjustment screw) mask the problem and make the engine behave. In order to get the engine in spec all fuel combustion affecting problems (including clogged CAT or holes in the exhaust pipe prior to the CAT) have to be fixed. Only if, after all that is done, the duty cycle is still not fluctuating close to 50% when the engine is running at operating temperature, it is finally readjusted via Lambda adjustment screw. … Then the engine is in spec and the duty cycle a full-value diagnostic tool for future problems. … ;)

Suitably to the title of this thread, I want to emphasize that when I pointed to possible contamination in the upper part of (some of) the FD‘s metering slits in post #38, I did that based on the OP‘s duty cycle readings in post #34. … Already the OP‘s initial duty cycle readings in post #1 were the basis for the quick detection of the o2 sensor problem. … And consider that, with the Lambda adjustment screw having been tampered with, these duty cycle readings provided reliable diagnostic information only to a minor degree.

Now imagine how valuable a completely reliable duty cycle can be for troubleshooting ! ... ;)

If my Lambda Control Thread and this thread does not convince DIYers & mechanics not to erase the duty cycle‘s diagnostic information by messing around with the Lambda adjustment screw or with the EHA adjustment screw, I'll be at my wits' end. ... LOL

And Yes as HD mentions there are two tests that can be done checking flow (without injectors connected to purely check the FD flow to each injector line and with injectors connected to check the injector performance)
These two tests not only 'can' but have to be done in order to provide (reliable) insight into the FD and the injectors. Tests solely done with the injectors installed (like in the videos in post #49) neither provide reliable insight into the FD nor into the injectors. … ;)

H.D.
 

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Discussion Starter #57
Heikkif, thanks for the direction to the fuel pump, I'll have a look at that first thing when I get back into the garage.

H.D., as a newbie, your posts are excellent because they are fairly easy to follow when you really dig into it, and they
are very explanatory - not only WHAT to do, but WHY. I have always found I remember procedures better when I know why I am doing them, not just following directions. To that end I feel very comfortable moving forward and testing the FD and the injectors as described. I have reviewed multiple youtube videos now also, and the more I see what is happening and why, the easier it is to understand.

It has become very obvious that one can mask problems by adjusting the Lambda screw, but eventually the 'brain' of the car (CIS-ECU) takes control and in trying to get things set right, other problems will show up and cause owners/mechanics to look at the secondary effects rather than going for the primary problem.... because they just didn't know. As an example, my mechanic friend is incredibly knowledgeable and has worked on foreign cars his entire 50 year career. He gets it. And yet, he was adjusting the screw to try and get the idle correct. When that didn't work, we started chasing other potential causes. Had my lambda screw not been messed with (prior to his doing so, I believe it was done before i bought the car - by a MB specialist), i would have had a much easier time seeing what the problem(s) was/were simply by testing the DC appropriately.

I really hope other owners see this thread and read through it. If they want credible info as to why their car is not operating properly in regards to anything to do with the fuel system, this is a valuable storage area of information! Along with H.D.'s other threads (Initial Lambda Adjustment screw thread), there should be no doubt... this is where to start when you have issues.

Once again, my gratitude to all that have commented and contributed. Special thanks to H.D. for putting up with my amateur questions, answering some emails, and hanging in there!
 

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Couple of things.

Randtor..just curious. When you full throttle, do you get the normal/expected upshifts from gear to gear? Mine hits redline, but wont upshift. Linkages are adjusted properly near the firewall, and it was suggested awhile back to change my FPR. (I have a new one, just havent had time to replace yet). She downshifts just fine, and under partial throttle, she upshifts/downshifts perfectly fine. It's only under 100% full throttle (which I rarely do in this car) that she holds the gear and wont automatically upshift. Its almost as if because the downshift button under the accelerator remains depressed, that it wont upshift. As soon as I let up just a bit on the gas after full throttle? She will upshift just fine.

Also..have had my eye on this one for awhile. I may get it
 

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I have reviewed multiple youtube videos now also, and the more I see what is happening and why, the easier it is to understand.
I generally recommend to take info & advice about the KE-Jetronic with a good pinch of salt. ;) … A lot of it on the internet (also on youtube) is erroneous … and reveals basic misconceptions about it.

... my mechanic friend is incredibly knowledgeable and has worked on foreign cars his entire 50 year career. He gets it. And yet, he was adjusting the screw to try and get the idle correct. When that didn't work, we started chasing other potential causes.
Even at big MB workshops in the 1980‘s there were only 2 or 3 mechanics who were sufficiently qualified to diagnose CIS-E engine issues to the (limited) extent described in the WIS (Workshop Information System).

Had my lambda screw not been messed with (prior to his doing so, I believe it was done before i bought the car - by a MB specialist), i would have had a much easier time seeing what the problem(s) was/were simply by testing the DC appropriately.
Correct. … Unfortunately, most garage mechanics, let alone DIYers, have no idea how good an idea the difficult to remove anti-tamper ball in the adjustment tower was/is and how bad an idea messing with the adjustment screw is. … ;)

I really hope other owners see this thread and read through it.
… and let‘s hope it will not be used to discuss things that have nothing to do with its subject.

Special thanks to H.D. for putting up with my amateur questions, answering some emails, and hanging in there!
You‘re welcome, Rand … and thanks for your appreciation. :)

H.D.
 

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Discussion Starter #60
Couple of things.

Randtor..just curious. When you full throttle, do you get the normal/expected upshifts from gear to gear?
Also..have had my eye on this one for awhile. I may get it
Hi Lesguy... I do get normal upshifts when giving it full throttle. That has never been an issue. Just the hesitation and stumbling. Sorry, it appears your problem may be different than what I have been dealing with.
For a smoke machine, rather than spending heavy $$$, you can make a decent one for short money:
and another:
If you type the query into youtube and do a search, you'll find many different examples, this is just one. There is also a video of someone using a propane mini tank to locate vacuum leaks,.
 
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