First issue in my SDL

I was driving on the highway doing like.. 70 and The car starts to bog down then get back to speed. Hmmm.. weird. Well Hattie did say I should get like 450-460 miles on the winter fuel. So I make note and get fuel on the next exit. Well it does it again so I start to get over just in case I loose power.

Go and fill up.. 22.5 ish gallons to the first click.

yikes.

The low fuel light never came one. but when I turn the car on it lights up.


is this the usual, pull the tank sender out and clean it, etc etc.

is it in the same spot as the W123?

I also need to clean the tank vent line since when I opened the filler it sucked in air/released a massive vacuum

Cyrillic Pictograms Below

AND my usual unsolicited solution

Attached Thumbnails

       

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'84 300SD sold
124.128

The low fuel light contacts in the fuel sender may be dirty/corroded, a simple matter to disassemble and clean. Sorry I can't help with the location of the sender in an S-class.

You didn't say what the fuel gauge was reading when the light didn't come on.

The tank vent may be OK, it needs about 1/2 psi difference (inside to outside) to vent. There's a spec somewhere, I disremember exactly where I saw it. With a tank that is mostly full of air, 1/2 psi will feel like a lot. My '87 300D does that occasionally, especially if there has been a relatively large temperature differential between cold-morning and warm-later.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

My W126 low fuel light is on all the time...we just need to combine the two...

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

the pic helps. I'll probably pickup some startron when I am by the west marine next week.

Startron alone may not be enough to get the low fuel contacts clean. Try soaking the sender (after removal) in Simple Green, then compressed air, then more simple green, then test with ohm meter, if good, wash in hot soapy water then blow dry.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

That tanks clean, don't waste your money on the Startron. The vent should be fine I checked it a few years ago when I pulled the tank strainer. All car fuel tanks presurize a bit. If the vent was plugged you wouldn't be able to go full bore when you fill it up with at the pump.

I don't have the manual handy, but the low fuel light is probably tripped by contacts on the float. I know it was working fine last year, so they are probably just dirty. I have never pulled the sending unit on one of these, but I think you can get it up top, if you took the rear panal out in front of the trunk its probably right there. Run the tank down and pull it.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200