I use a 46MM socket or a HUGE pair of water pump pliers to remove the senders from the W123's .

The same sender is used in some W126's, I forget the interchange .

I've had very good luck cleaning the gunked up ones, as mentioned they're usually full of black crud that gets into every dang crevice so you'll need a soft bristle brush and some serious de greaser to dissolve and clean it all out of the nether regions, then lay the parts out to dry well before re assembling .

There's a fractional size 3/4" drive socket too, I'll try to look it up to - morrow, a $6 socket @ Harbor Fright or less at your local pawn shop .

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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

It's 46MM or you can use a fractional 1-13/16" socket, it fits snugly and won't slip .

I only use 6 point sockets on alloy fasteners .

This 1-13/16" socket is normally a 3/4" drive so you'll need a 3/4" male to 1/2" female adapter then the job is dead easy ~ use a flex handle from in the trunk, some times you'll need a cheater, I use a 16" long piece of thin pipe that's lightweight and slips easily over the flex handle .

__________________
-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 am not sure that this is necessary or even a good idea. I never mix gas and diesel because of the issues with injection pump and injector wear. Granted, they did this in the 1950s, but the Bosch injectors were stouter and not electronic and the fuel injection pumps of that era have their own oil reservoir, designed to be filled with 20-30W oil

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6

I used mineral spirits (paint aisle at the home center) with good success cleaning the sender.

Be careful there are delicate wires in there and you don’t want to break them. Two of them are resistance wires and the third is regular copper. Be sure the contacts on the slider are clean. Two contacts short the resistance wires to determine the level and the other contact closes at the bottom to light the low fuel indicator via the copper wire.

Also be sure to remove the seat cushion and back rest, and lay down plastic. It will drip and leave your car smelling like a truck stop if the fuel gets into the interior fabrics and seats.

It’s easy to test outside the tank, once you’ve cleaned it. Just plug into the harness and tip back and forth (let gravity move the slide) while watching the gauge.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Talked to new owner. He pulled fuel level sending unit and it was gunked up. He is going to try the additive first and if that does not help he will pull tank screen.

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Jim

Biocide the tank.

I would hand clean the sender.

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-Typos courtesy of my mobile phone.

Just so ;

Failing to clean the sender first just means he'll be chasing the fungus longer.....

__________________
-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

If he isn't able to get it working after cleaning, Pelican offers sending unit 123 542 0404: Mercedes-Benz Fuel Level Sending Unit - Uro Parts 123-542-04-04

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Event Video: Cars & Coffee 2023, Simi Valley CA: https://youtu.be/CFfY9CPVuEs
URO Parts online catalog: https://apaindustries.com/catalog

Tell him he bought it he fixes it. But he wants a warranty huh?

No actually all he has had is praise for the car and is glad to have it.

Potential fuel issues moving the car from south Ga to Chi Town never crossed my mind. If I had known it was going to have this issue I would have taken care of it before putting it on the truck. Down here the car did more sitting in the garage than out being driven so that probably had a lot to do with it too.

I invited the new owner to join but don't know if he has or not.

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Jim