I am a retired North Pacific commercial fisherman and currently farming(livestock and hay). I also have a small stable of W123 diesels either restored or under restoration. I have Three 4wd tractors. All the tractors I have owned and the commercial fishboat engines as well as the gensets have had both primary and secondary filters and some have filter screens like the MB diesels. Our fishboat engines used Racor fuel filters made by Parker. They are not cheap. Almost our whole fleet used them. Racor makes replacement filters in sizes from 30 microns down to 2 micron media. They have large clear plastic bowls and a water drain as well as heating elements and pressure gauges.. Some are very large as were our boat engines. The fuel available in BUSH communities is often old and contaminated with debris, algae and water and having an engine quit in stormy conditions in the Gulf of Alaska can be fatal . I always added 2 micron filtration as the final filter before the injection pumps. The point of this post is to suggest adding improved filtration to 240 and 300D engines to extend the pump and injector life of these aging diesels. I think the MB filters do an adequate job if serviced regularly and I have read their micron specifications as high as 20 and as low as 6 microns from company websites. In my experience there is no such thing as fuel that is too clean and filtering down to a few microns is desirable. Obviously too fine a filtration will lead to restricted supply if placed as a primary filter. Once I place my 2 micron filters as the final filter I rarely have had to change them. We change our filters based upon fuel pressure monitoring. The upstream filters are the ones we service which are of course Racors. The fuel lines on the MB diesels with their hard plastic and banjo terminations are an obvious problem and so far I haven't placed 2 micron filters as filters before the IP. I have placed a 5 micron Racor filter just after the plastic screen filter in my 240D. Here is my suggestion to lead off to this discussion. Why not add a 1 or 2 micron filter on the return line to the tank? Great access with just hose clamps before the cigar hose. My other suggestion is to install a "fuel polishing" system which we also used on my last big boat. This is an electric pump constantly circulating fuel from the tank through a 2 micron filter. In our boat we ran it 24/7 during the season as a way to watch fuel quality since we sometimes pumped fuel from rusty drums on shore. We mounted it by the helm so we could always spot trouble ASAP and we had a vacuum gauge set to a light and bell alarm to alert us if the tank fuel was problematic. These are the 2 options I am considering. The return line filter is certainly the easiest but I do not know how much fuel flow returns to the tank and whether it is ample enough to do much good. Anyone out there with Ideas on this project? BTW, Baldwin and CAT make 2 micron filters for use on big rigs beside Racor. I should also mention that we put hard hours on our tractors in frequently dusty conditions and I regard fuel and air filtration as well as frequent oil changes as mandatory maintenance. Our tractors also have fine micron by pass oil filters. They run flawlessly and I have yet to service the pumps or injectors.

Good ideas, but of questionable necessity in the mostly urban setting. Most of these things already have 150k+ mi using the stock system. If there was fuel system damage to be done, it's been done long ago... That said, never a bad idea to have cleaner fuel

However, the quality of fuel coming out of a refinery is pretty damn good. Storage and transport is kinda iffy. Lotta guys just put a bigger spin on filter on the return and call it good.

Will super filtering your fuel help the longevity of your fuel system, probably yes, however it woulda helped tremendously if you started when the vehicle was brand new. In all reality, if you're in the urban setting, it's probably not worth the effort, and your $$ would be better spent on occasionally using Diesel Kleen and cleaning/maintaining your fuel tank/system. Using pump diesel, you'll probably see more problems with w123 tank degradation and clogged up primary filters

There are other brands of vehicles that could use better filtration like my diesel Ford truck. But, I think when you get into the details, I think MBZ probably overdid the filtration. I would be more concerned about adding a diesel additive to provide more lubrication to the IP. If you have a clean fuel system -- which is really just a question of what has been done historically to your particular vehicle -- I think you will find there are a lot of other issues on these cars that are more pressing.

Dkr.

Yes people have installed Racor's and some of the other brands of water separators. Note that there is some space limitation.

The below thread is mine and I have the CAT 2 micron Fuel Filter as the secondary on mine. I have only once and poor Fuel get into my tank and it was not filter clogging stuff it just did not burn well.

Lower than 10 Micron Fuel Filter Mod pics
Lower Micron Fuel Filter Mod

CAT Fuel Filter Mod by Cho
2 Micron fuel filter CAT
WIX Filter Base 24770 for CAT fuel filter; Baldwin Filter Base for CAT filter FB1311 Fleetguard 142784S; Fleetguard Fuel Filter/Water Separator Base (or Head)
Part No. 014278400/142784S; CAT Fuel Filter Base/Mount part # 280-2698

Fuel Polishing
Fuel Polishing Idea
Diesel Fuel Cleaning / Polishing help?

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84 300D, 82 Volvo 244Gl Diesel

I am adding a water separator to my 300d because I've seen what water
can do to an injection pump.

I'm running a high quality Racor 500 copy with a 30 micron water block element as a primary filter, and a Cat 1R-0750 2 micron filter as the secondary filter.

Lots of issues due to contaminated fuel before I installed this upgraded filtration, no issues since.

It's also completely overkill for just about everyone. Almost all of these engines run the factory filtration, and the injection system outlives the engine and car.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Well thank you all for your unexpectedly excellent posts and suggestions. I missed most of these links with my search. I also should say I trust the MB engineers to know something about diesel fuel going into diesel engines . They invented the beast after all!I have the cat filter setup new in a box and several other filter bases from years past as well as some Racors and it is just a matter of deciding which one to use but I think adding improved filtration is important no matter how many miles and a system to keep water out of the system is very important. My new MB project car(a 1984 300 wagon) has algae in the fuel(came from Oregon) and that begs some new efforts. I will be adding Racors or CATS to our 2 12 valve Cummins farm trucks because their fuel filter access is worse than horrible and only have one primary except for a screen in the tank. There is room on the Passenger fender side on my 300D because previous owner removed the hydraulic leveling system along with the AC. My only little question is how to adapt conventional fuel fittings to the banjo bolt system MB uses without causing leaks?? Ideas there?

You can thank DeliveryValve for prompting that particular thread.

In the past most of the Secondary Filters on Diesels were around the 10 nominal micron level. That included CAT Diesel Engines.

I can't remember the details of the article but CAT did some research and decided to create their 2 Micron filter. Notice I did not say they invented 1 micron filters. Anyway CAT decided it was worth while to filter down that level.

On the Mercedes if you install the CAT filter CAT 1R-0750 as in my thread it is not a water separator but the filter itself is at least quart sized. You would have to take on near that quart of Water for liquid water to get into your Fuel System.

This is from my notes:
but CAT changed their rating standard. “Advance Efficiency” 1R-0750 became a 5 micron filter. The "Ultra High Efficiency" line of filters has a value lower than 4 microns filter or the so called 2 micron filter. See on page 11 of the CAT .pdf doc published in 2013 attached or a direct
link.. https://caterpillar.scene7.com/is/content/Caterpillar/C10467200


The abrasives in the fuel can over time wear down injection components and replacements will be needed. Both the Baldwin and CAT filters are rated at 2 microns. According to the Baldwin Rep, the BF7591-D has an efficiency rating of 91.95% for less than 2 microns. The CAT 1R-0750 has an efficiency rating of 98% at 2 microns. The stock filter is rated at 10 microns nominal. Meaning 50% efficiency rating at 10 microns. CAT did a study and using a 2 micron filter increase life of fuel injection parts by 7 fold compared to using a 10 micron filter (again is stock)."

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84 300D, 82 Volvo 244Gl Diesel

Thanks 911. I have a lot of diesels(tractors, trucks, MB cars) that I like to feed clean fuel to. I try to standardize them all. The trucks get big racors as primarys mounted to the frame(10 micron with water trap and heat elements) and the secondary are 2 micron Racors. Ditto the tractors. On my MB diesels I added 2 micron filtration after the screen filter but before the pump. I don't like filters before the pump on the vacuum side normally but the banjo fittings on the MB s keep me from messing with them. On one car I put the IR750 CAT after the screen filter and the other has a Racor 2 micron. Both bolt to the Driver fender. The big CAT filters are pretty sweet and I think I will add a vacuum gauge to monitor replacement rather than doing it on a mileage basis. They may not plug up. I had a 2 micron filter plug up on one of the trucks after just a few months.

If you are willing to go to regular fuel hoses the banjo fittings are not an issue as far as mounting filters goes.
When I added the CAT filter I switched the plastic tubes to rubber hose.

Not much of a trick to get the plastic hose/tubing off. You tape both sides of a vice Grips jaws so it won't ding up the sealing area of the banjo and you get a torch or a candle and heat up the plastic tubing that goes over the barbed end just enough to soften it so you can yank it off with out leaving any plastic on the barbs.

If you over heat it you melt the plastic to the bar and or when you tug on it the the plastic stays on the barb and you need to carefully cut it off.

I know people like the translucent plastic tubing because they want that feature incase there is an air leak and they think they are going to see the air bubbles. But the truth is the tubing is going to get dark and none of the other diesels I have worked on have translucent fuel lines. Trouble shooting for air leaks has never been on any of the stuff I have worked on. Especially on the Mercedes where the hose lengths are shot and cheap to replace.

The newest type of hand primers don't seem to be a common cause of the air leaks like the older on.

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84 300D, 82 Volvo 244Gl Diesel

If you cut the plastic hose off the banjo fittings, the banjo fittings have just a hose barb connection which will work with standard 5/16" or maybe 3/8" fuel line and hose clamps. I forget which size. Then just use ORB and barb fittings to fit your Racor or whatever you choose.

Here in Oregon all diesel is 5% biodiesel, and the biodiesel will destroy fuel line which will handle gasoline all day long. If you have something similar in your area, or will ever travel in such an area, be certain the fuel line you use is biodiesel rated. I used Gates Barricade hose. ~7 years and 50k miles later and all is well.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Regular auto part stores sell: Goodyear and Gates both make Fuel Injection hose that is Viton lined. The Goodyear hose has a blue lining and the Gates hose has a brown lining.
Fuel Injection Hose GoodYear and Gates SAE J30R9 or 30R90 SAE 30R9

A thread on the subject:
Will "fuel injection" hose withstand biodiesel?

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84 300D, 82 Volvo 244Gl Diesel

Thank you folks. I'm on it!

Hugh ;

Please keep us posted .

I live in Southern California and have gotten many a bad tank full of pump Diesel fuel ~ one time far from home the Chevron station was pumping out what looked like TEA and it glogged my filters, tank screens and so on .

I don't think you can have too much filtration, like you I learned this from BOATS .

The clear bottom of a filter makes the only water trap I'd trust .

I'm keen to see what / how you address this .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I really appreciate the comments from you guys and rather than cut out the banjo lines, I decided to put in the Big CAT IR-0750 filter on the suction side after the plastic screen. It worked fine for 5 minutes until the engine started to choke and rock and finally quit. After I went back to the stock setup all was well. My lesson(I think) is that there was too much resistance to suck the diesel thru a 2 micron filter. I did double check to look for air leaking into the system and the clamps seemed tight. I think I will try 911's set up with the 2 micron CAT after the MB spin on or I might try a clear bowl Racor with a 2 micron as the secondary. I also wondered if putting a 2 micron on the return line might be a nice touch. I do not know the IP flow/pressure parameters for the Mercedes 617 and maybe the flow is too low to do much. On our Cummins pickups the return flow is pretty hefty and it returns at over 20 psi which should be ample to punch thru a 2 micron filter. On our farm we get a lot of our diesel in Jerry cans and in old tanks and keeping things clean with funnels and such introduces the risk of dirt getting into the tanks. We normally use road diesel and not red fuel because our local Wyoming stations do not supply red fuel that is winterized. We always use Power service white and gray jugs to head off jelling and lube the injection system. I must finally say that when winter really hits with lows from 0 to 40 below from Dec thru February, owning diesel cars and trucks seems kinda stupid. That must be why I drive my wonderful 2001 Corolla with a big battery and Blizzak snow tires which has started at -37 a few winters back.