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1980 450SL named Freya. 202,000mi
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574 Posts
Discussion Starter #1 (Edited)
-- EDIT: The actual rebuild starts on post 17. Below is some background.


Okay, so in some other threads, I (we) have come to the conclusion that my fuel distributor is bad, dumping fuel into cylinder one.

Corroborating symptoms:

1) Black, carbon fouled plug for 1 (all other plugs clean).

2) Missing at idle is not as bad after an extended freeway run (indicating the freeway run helped clear fouling). Missing at idle is worse after stop-and-go traffic, indicating that low RPMs increase fouling.

3) Missing is mainly at idle and RPM under 2000. At 2500+ and under load (freeway) car is super smooth - this indicates that cylinder 1 is now getting closer to the correct mixture, as all the other cylinders are now using much more fuel at high RPM and under load (in a sense, cylinder 1 then "catches up" and preforms closer to the other cylinders).

4) Injectors are all new - as you may recall I originally replaced injector 1 thinking it was leaking and dumping too much fuel into cyl 1 - obviously the injector *may* have been damaged or weak, but the real culprit here is the fuel distributor.

5) There has been occasional fouling appearance on the plugs for cylinders 2 and 5 - both right next to 1 on the fuel distributor - this indicates that the diaphragm failure may intermittently be spreading to cylinders 2 or 5.

THE FIX

I attempted to contact CIS Flowtech, as well as SpecialTAuto to inquire as to current stock for my car, but neither got back to me in a timely way. In the meantime I found several rebuild kits on Ebay. One located in Florida, and the other in San Francisco. Both promised Viton o-rings and new technology for the diaphragm that is said to be impervious to ethanol. I went with the American Precision Machinery version (CIS-Jetronic on ebay) as they were closer and I'd get it sooner, though it was slightly more expensive.

cis-jetronic | eBay

I received it today. $94 and free shipping. Kind of expensive, but certainly less than a remanufactured unit. And I get the joy of doing it myself.

LOL.

The replacement diaphragm is very thin. It is a nylon mesh supporting a rubber type of material (viton?? Nitril?) The kit also comes with a complete set of viton Orings.

MY PLAN

My plan of attack is to do a "minimal disassembly" - in particular I want to avoid even toughing the individual adjustment screws as I don't have access to the special Bosch tool for aligning the flow on each port. I also will be keeping very careful sorting of the parts, so that all springs and valves go exactly back to the same port they came from.

I will not be doing an ultrasonic bath, but I will be spraying and gently cleaning all the little ports in the unit. With the amount of fuel system cleaner that has gone though my car in the last two months, I actually expect the interior to be fairly clean.

The single main pressure regulator is adjusted by means of shims, so I will be replacing those o-rings. As this car is LAMBDA equipped, I am running on the assumption that the lambda system will take up any slack where I may be off in adjustment.

Except of course for the individual channels, and as I said I intend to leave those alone.


I'll be tackling this tonight or tomorrow, and will of course provide further images and discussion.


Here are some images of the rebuild kit. Note on the second image, the diaphragm is really a paper-thin piece. I'm not sure how the material will compare in stretch to the original, or how that may affect system pressure or differential channel output - but we're about to find out!

 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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30,384 Posts
I attempted to contact CIS Flowtech, to inquire as to current stock for my car, but neither got back to me in a timely way.
Surprised.

Larry answers his phone personally and will talk your ear off with advice.

Everything about Larry and his business is done in a timely fashion.
 

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1980 450SL named Freya. 202,000mi
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574 Posts
Discussion Starter #3
Surprised.

Larry answers his phone personally and will talk your ear off with advice.

Everything about Larry and his business is done in a timely fashion.
Perhaps he's on vacation. I sent an email, and a week later got a response from "German Star" who said he was a sister company of Flowtech.

Though, I didn't call - well, I'll be calling if I screw this up on my own, LOL.
 

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.


The GermanStar who was formerly an administrator and supporting vendor here at BenzWorld recently sold his business of the same name and retired. Was not aware Flowtech was the buyer, if it is the same GermanStar in question.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
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30,384 Posts
Perhaps he's on vacation. I sent an email, and a week later got a response from "German Star" who said he was a sister company of Flowtech.
GermanStar used to buy his FDs and WURs from Flowtech. He used to get pissed when people went directly to Larry.

Maybe something happened....don't know.

I bought and FD and WUR from Larry in June....no problem.
 

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300sel W109, 280S 70 , 220s 62. 230 66. Lancia Flavia 63.Pininfarina
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869 Posts
Should be a Interesting rebuild ,hopefully goes well.
Good luck.
Ad
 

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1976 450 slc
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422 Posts
Used a cis jetronic kit to rebuilt my cast iron distributor a few months ago, top quality stuff.
Cast iron kit uses two gaskets & stainless steel diaphram, different to your rubber one.
Solved my issue of 2 sooty plugs & slight idle stumble, could clearly see the dints
 

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1976 450 slc
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422 Posts
In the diaphragm of the offending ports- follow the rebuilt tutorial on the CIA jetronic website or eBay page, one tip, use guide bolts when assembling, makes the job a lot easier
 

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300sel W109, 280S 70 , 220s 62. 230 66. Lancia Flavia 63.Pininfarina
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869 Posts
Great! Please share the kit source as some are better .
 

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'79 450 SL.. '13 Escape SE 2.0 Turbo...'06 Hummer H3....'84 Ford F-150 HO..'62 TBird Convertible..
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I'm surprised about your experience with Larry too. When I was doing my '79, he told my mechanic to call him with any questions when we were chasing the all too common fuel problems..Ended up sending my FD and WUR for him to rebuild..Quick and professional..Keep his # handy !!
 

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1980 450SL named Freya. 202,000mi
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574 Posts
Discussion Starter #11 (Edited)
Rebuild done, went quick and easy... And... No more missing!!!

I'll post pics and tutorial tomorrow, I am JUST NOW going to bed. The reinstall was the hardest part... And then of course I did my favorite part, the VERY LONG test drive on the empty early AM freeways...


But doh, I drove so far I had to deal with incoming traffic to get home, LOL.
 

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560SL,380SL
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The one thing that you can't do, that I assume CIS Flowtech, etc probably can, is individually tune each port via the springs and their adjustments on top of the pumpkin. If you don't have the equipment, no touchee -seriously. This worries me. Although I've done two of these and they seem OK on the car, but there was no guarantee that those adjustments were perfect "before" or "after" I did this. This would take a bench setup that would probably cost into four figures to build right.

On both of those FD's, I found the hardest part to be cleaning the slots truly thoroughly. Obviously, you can't do this mechanically and I suspect that too much air/fluid pressure will damage them. A neat trick (well, I thought that it was, anyway) that I used was shining a laser pointer through the slot, and kept cleaning with brake fluid until I saw nice, sharp, even, clean, projected slots.

There's no point in doing any of this without the main pressure regulator being "right". I am certain that replacing that (very oddly/cone shaped) molded rubber piece with a o-ring will throw it off. AFAIK you can't get the shims from MB without buying the kit. I bought some bar stock (exact diameter) to make my own with but I'm still at a bit of a loss as to how to cut it.
 

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'82 380SL; '95 Defender D90; '78 450SL; '14 328d; '02 540i Touring (sold); '83 280SE euro (sold)
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Congratulations on your perseverance and going through with it.

I did mine using the same kit a couple of months ago and got rid of the issue with my 2 sooty spark plugs and rough idle. The most time I spent was separating the two halves even after following the instructions and heating at waiting it was almost impossible and stuck together really well. Finally after my 4th or 5th attempt I got it separated.

After opening it up all looked clean inside but the only thing I noticed is how deformed the diagram was even though there were no tares or cracks in it. ImageUploadedByAG Free1416506242.370971.jpg

Have fun with your other projects!!!


Sent from AutoGuide.com Free App
 

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1980 450SL named Freya. 202,000mi
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574 Posts
Discussion Starter #16 (Edited)
The one thing that you can't do, that I assume CIS Flowtech, etc probably can, is individually tune each port via the springs and their adjustments on top of the pumpkin. If you don't have the equipment, no touchee -seriously. This worries me.

On both of those FD's, I found the hardest part to be cleaning the slots truly thoroughly. Obviously, you can't do this mechanically and I suspect that too much air/fluid pressure will damage them. .
Yes I was concerned about upsetting the fuel balance so I didn't touch the adjustment screws or the main pressure adjuster.

I have an idea for a DIY channel flow measuring device to allow you to individually measure each channel for proper flow. While I'm sure the Bosch tool is very expensive and no longer available, I think you could build one using some old fuel lines from the junkyard with the proper fittings, and some common lab equipment such as graduated cylinders..

250ml Polypropylene Graduated Cylinder | U.S. Plastic Corp.

As for cleaning as I'll demonstrate in the post below, my distributor was extraordinarily clean I didn't have any problems cleaning the tiny little slots.
 

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1980 450SL named Freya. 202,000mi
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574 Posts
Discussion Starter #17 (Edited)
THE REBUILD ILLUSTRATED

Okay, so here is a recap of the "down and dirty" rebuild of my fuel distributor. If you've rebuild a carburetor (remember those? LOL) then you should be able to handle this.

NOTE: The procedure I outline below is NOT the "most optimum", it is the "minimum required" to get your fuel distributor working again.

Some omitted tasks: No total inside and outside cleaning, no ultrasonic bath, no replacing o-rings on flow adjustment screws, no post flow or pressure adjustments. The case was opened using the "expedient" hammer technique.

Mainly, I focused on the critical tasks, cleaned the most critical areas, and replaced the O rings and the diaphragm.


REMOVAL FROM CAR

No pictures for this, as it is fairly straight forward. But NOTE: I highly recommend removing the fuel line from injectors 2,3 and 4. These fuel lines are particularly short, and you'll end up bending them to get them off the fuel distributor. When you try to replace them later, you will NOT be able to get them on, until you remove them from the injectors. Best to remove from the injectors now and avoid bending the lines at all. Interestingly, lines 1, and 5 thru 8 are much easier to deal with, as they have longer and more bends in them that allow enough flex to R&R without disturbing the injectors.

The three screws that hold the FD to the Air Sensor will be stickily - use a large blade screwdriver and be careful not to strip them.

In removing the FD, mine has a metal tab that holds the plunger in place - not all do, so be careful you DO NOT want the plunger to fall out, as it is easily damaged.

Cover the hole on the air sensor where the FD goes with a rag.


ON THE BENCH

There are a couple key things you need:

1) Something to hold the FD while you are working on it. I had this 3.5" PVC coupling (the white tube) that worked perfectly, as it held either the top or the bottom level.

2) An egg carton or other means of keeping the parts separated and IN ORDER.

3) Cleaner. My first choice was brake cleaner, though as I ran out I also used B12 carb cleaner.

3) WD40 for assembly lube (mainly the Orings)

4) LINT FREE rags or wipes.

5) Torx T-27 bit

6) SMALL hammer

7) Tweezers

8) The rebuild kit (I used the APM version from CIS-Jetronic on EBAY)


Here is the FD, sitting on the 3.5" PVC tube.





We'll spray and wipe off most of the outer gunk, especially around any fittings and the plunger.

Unscrew the retainer and nut.



Then remove the PLUNGER (and spring) and CAREFULLY set it in the egg carton other other SOFT CLEAN place where it won't roll.

Clean the area then MARK with a sharpie the position of the key in the valve barrel. NOTE: make sure you don't erase the sharpie mark when cleaning!




Now unscrew all of the TORX screws on the bottom (T27). Unscrew in a criss-cross pattern per mechanical standard practice.

You'll find that the two halves of the FD are well stuck together. to loosen them slightly, I put a torn screw in for about three turns of thread, then LIGHTLY tapped it with a hammer. I did this for a couple perimeter screws, and that was enough to separate the halves by a mm or so.


Hold the bottom (the upper piece seen here) and LIGHTLY tap the screw with a hammer. LIGHTLY.

Now, USE YOUR HANDS, and carefully separate the halves. On my distributor, all the springs and bits that might fall out are in the TOP portion, so for me, I kept the unit upside down as I separated the halves. Be very mindful of a pieces falling out!!!

Here is the bottom - as you can see the interior of my FD is very clean (keep in mind that I had used multiple Techron and SeaFoam applications in the preceding months).




And here is the top with the diaphragm. The diaphragm looks intact, but when held up to the light there are two VERY SMALL (near microscopic) pin holes. that's how sensitive this thing is - a tiny pin hole and it's shot.



Under the diaphragm, we see the springs and the ceramic valve tops. They are stuck to the diaphragm (not sure if that is due to use, or they were glued in place at factory assembly time - but the two little dots on top indicate to me, glue. I will not be using glue in the rebuild).




Remove the diaphragm, and examine it against the light, looking for pin holes, as an affirmation that the diaphragm did in fact fail.

Then remove the ceramics and springs. KEEP TRACK of where each spring/valve came from. The method I use is to pick a recognizable point on the FD, and then take them out clockwise starting at the top - and place them in the egg carton clockwise. Then on reassembly, I just reverse this, taking them from the egg carton clockwise.



Don't forget to remove the spring seats - keep each one with its respective spring in the egg carton.



Continued next post
 

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1980 450SL named Freya. 202,000mi
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Discussion Starter #18 (Edited)
NEXT, remove the center valve - it will be tight, just pull it out. The little o-rings on the fuel slits will mostly just fall off. The other orings may disintegrate or break. There are two on the barrel, and one in the bottom housing (plus the 8 little ones around the slits).



CLEAN the barrel thoroughly. Especially make certain the very small slits of the fuel metering portion are clean and clear of all debris. I used a very soft nylon brush and brake cleaner to clean the interior of the tube.

You may notice that after I completed external cleaning and disassembly, I changed my yellow gloves to clean nitril gloves for final internal cleaning and assembly.


Remove all the old O-rings, and coat the new orings in WD40, and slip them on. Then insert the barrel back into the TOP of the FD. Mind the KEY and the sharpie mark you made on the CASE. Especially, ensure that the fuel slits line up with each fuel port to the valve.




Then, replace each spring seat, spring and valve in the exact same port it came from. My springs and seats were perfectly clean, but I did spray cleaner on the ceramic valves, as they were just a tad dirty.




Next, wash the diaphragm to remove the protective white coating and let it dry. Then center it on the top. You see an indentation on the edge that lines up with the FD case, but MORE IMPORTANT is the small hole that MUST line up with the WUR port.



WUR holes must line up!!



Now, align the bottom half, and using both hands, gradually press the halves together, making certain that the ceramic valves remain centered on their springs. Using the 3.5" PVC pipe helps to keep the assembly level as you press the parts together.




Then replace all of the torx screws. Remember to use a criss-cross pattern when tightening.

One thing I am concerned about is this scoring on the upper portion of the plunger. I considered using very fine (1200) paper or some sort of polishing paste, but decided to leave it as is. I believe there is a similar scoring inside the barrel.




Reinsert the SPRING and the PLUNGER, and then reattach the nut and retaining clip. I'm not clear on if this FD model is critical on the nut and barrel distance, so I just tried to keep the orientation as it was on disassembly.


Remember: always take lots of pictures as you go along for reference!



BACK ON THE CAR

Oh man, when I removed the FD I did not removes the fuel lines from the injectors. It was impossible to get lines 2,3, and 4 back on without first removing the lines from the injectors. I wish I had started out that way. The other lines re-connected easily.

One note: this rebuild kit did NOT have the two copper crush washers for the frequency valve attachment, so I had to reuse the existing ones.

Before I connected the injector lines to the FD though, I did a quick fuel test. I jumpered 30 and 87 using a banana cable. This activated the fuel pump, and I then took a video of the fuel as I pressed on the Air Sensor Plate:



And here's the video:



Now, on to road testing. Hooking up my duty cycle meter to my ECU mod (that allows you to use a standard duty cycle meter) I'm ready to go!.




Initial start was hard, including a bit of backfire - but once started, it was clear the engine was running better. AND LEANER. The lambda system was trying hard to enrichen the mixture. After driving a bit to get it warm, I worked on the mixture until I got idle at 50% to 55%. NOW, under load I never see Lambda try to lean out to less than 30%. Max enrichen (coasting downhill at freeway speeds) will still climb up to 90%, and I believe is normal.

Car idle is now a SMOOTH hum.

Here is a before and after at the tailpipe:



All I can say is YAY! And thanks to everyone for all of their help!!!!!!
 

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