How to Repair Your Fuel Sending Unit 

On my 85 300CD, the gauge would typically show FULL when I filled the tank and would then hang up at about 3/4 tank. The ODO would show another 100 miles going by with zero change on the indicated fuel. As Pierre states, the float MUST be free to slide up and down those wires. Mine had a small accumulation of hard crud on them. I carefully removed it using a very sharp blade on an exacto knife. That was 30K miles ago. Its been perfect ever since. Easy job.

I think this was one of the most useful videos on the youtube for classic Mercedes lovers!! Thank you Pierre.

Thanks for this video! I bought a tank for my 1967 280SE and I'm glad I watched this video. Now I know how to prep the fuel sending unit for installation. Thanks again!!!!

Crucial tip for wire issues. The wires have to run through the little guides on the plastic slider in a mild S-shape. If the wires run straight along next to the slider you will not get a reading.

I just did this today; very straight-forward & well worth it! hard time getting the rear seat bottom to latch in though

Thanks for the video. It was very helpful. I pulled mine out and cleaned it. My problem was that one of the three wires was not making contact with the float. Re-routed it and it works great. I thought I would have to buy a special tool to take the sending unit out of my 1982 -300SD but was able to get it out using some large channel locks.

Pierre your videos are getting better and better. Unlike some people I know, that advice came free of charge. I would love if you ever had a repair seminar day at your shop. Have a one day charge per attendee and just give everyone there a general overview of the most common problem and possible fixes for the chassis 123, 124 and 126. 108 & 109 if there is any interest.

Thank you so much

Doing a tank job on my 300SD now. Thanks for the tip!

this was a very helpful video. thank you Pierre. Have the same sender on my W124 200 1998. got to take it apart now,

Ok guys before you purchase a new fuel sending unit try and clean the electrical connection on top of the unit first. Don't make the same mistake I did, and purchase a new VDO sending unit which didn't solve the gauge Fluctuating issue. I took the old one apart, and cleaned it up well put it back together and used a 220 grit sand paper to clean the electrical connection on the sending unit. It works perfectly fine now.BTW it's a 1995 E320

thank you! these are also easy to remove from the w123 models. so nice of you to create such a helpful video for us to learn from and enjoy. have a great day. cheers.

Thanks Pierre! Good stuff!

Great information. I have to do this on my 300SD. Thank you Pierre.

Great I,m going right to the garage and practuce what I just learned at video, gets right to the point.

Thank you Peter

Yes very helpful thanks

Awesome input

just the info I needed today!

thank you pierre

Thank You for the Info

Thank you!!!

Thanks 🙏 a million bro

Excellent.

excelente

Thank You for your informative video. Mine is a 74 230 and the fine wire broke. Hope I can route that wire correctly. Also mine has a 3rd wire and looks like to guide the float. I am going to use some new cooper wire which is the sending unit. Let you know if it works. VW

$280 is really not all that much money when one considers what things cost these days. Interesting and informative video. Instructional vids like this one are huge for the DIYer.

Getting stabbed.😂😂😂😂😂Got a rusty shaft 😂😂😂 Incredibly amusing and informative. Thankyou.

Negative on using a file to clean the shaft ! what you'r missing is the explanation of how the 2 thin wires run over one and under the very tiny brass tongues on either side of the float (not plunger!). Those wires get out of place here and need to be re-positioned to run over one and under the other of 2 tongues on each side..This is an extremely delicate re-seating, but doable with patience.. Also these same wires get snagged on the white nylon parts on bottom of the float.. They need to be freed and then running in the center of the square holes in the nylon. One will probably be good, so you will see how IT runs.. This too is extremely delicate. With them properly strung, the float should easily slide up and down the center shaft..And yes, clean out the inside of the tube and be careful that you get its notch seated onto the main top-cap witch has a matching male part it mates with.. Don't over tighten the little rubbery nut at the tube bottom.. Your gauge on the dash should now be reading properly. If not, try redoing the job..Then, if no go get one from another Benz at a Pick your Part for, what, $10.00 ?! ... Mark, Los Angeles PS. This could very well not be the problem. Could be at gauge or wiring to/from float....

does the wire snake through the contacts in an "S" or just ride them on the side?

Hi, can you tell me the size of the nut that’s holding the fuel sender on a 86 420sel W126 chassis ! Thanks.

Pierre how do you remove a fuel level sensor from a 1973 450SL that was one that was epoxied in place?

Is the fuel sending unit the same on a 1993 W124 wagon? If it is, how / where do you access the fuel sending unit on a W124 Wagon?

Hey there. Besides of the hole at the top of the pipe is there another one on the bottom? I took my sender out but I can't figure out how the fuel goes inside the pipe if it doesn't have a hole in the bottom. I'm confused, don't know what to do

Wat about the wires Bru? Aren't they sup to be running thru the contacts on the slide? Which way?

the very thin wire, that's 0.05 mm thick is the constantan wire that shows you if you are on reserve. it has a resistance of 292 ohms. it's usually not available in hardware stores as its resistance is very high.

what are the spec on the wires for the unit.

I have a 560 sel and the gas gauge just quit working! It is on empty! But the tank was filled. If it shows empty without a light does that mean no power to the gauge or no ground or something else

thanks for the great video as always my sec may have an issue with its sending unit. The reserve light will go on with 2 gallons left as it is supposed to do but the gauge needle still hangs around the middle rather than the empty area. when removing the sending unit, are there any precautions needed. Does it matter if the tank is empty or has gas? My car is an 85 500sec thanks

Pierre you have failed to respond to my question on how to remove the fuel sensor in a 1973 450SL that was one of the units that was epoxied in place. Please help me out.

I have a '94 e320 convertible and under the instrument cluster there is a box mounted with a dial on it with "I" on one end and "O" on the other. I can't find anything to tell me what this is. Can you help me?

Pierre, If you want to be proactive in regards to your fuel sending unit on a W126 sedan what can you do? I know on the W126 you have to remove the rear seat to get at the unit but how can you tell if it's going bad?? Nobody wants to wait till it fails so I wanted some tips as to know when your unit might be ready to go out on you. Can you tell just from looking at it once it's removed from the tank?

Did this on my w124 and pretty much the same principle applied. I just can’t get the small nut to start threading back on though.

I actually had to work with my sending unit a few months ago. The wires on my unit are broke. I purchase a used one on a near by yard, but would love to fix the original. Any good ideas on how to replace and fix those wire? Thank you in advance, great video by the way. (380 SEC 1983)

Just found your site . Any idea where I could buy a 85 300d air filter housing California car Thanks Tom

Is it the same sending units for gas and diesel?

Hopefully its the same principle on the 115.

Pierre I have a '79 w123 230 carburated and the fuel guage only reads until the tank is half full and then completely drops to zero when its less than that. sometimes it occasionally works when hitting a bump or just tapping on the sending unit itself. could this be a matter of just cleaning the internals ?

Is there a fix if the wire is broken?

250c has 8 little bolts to screw out. Gauge not working. Need to drop tank and get at that. Should not be too bad.

I mean Pierre.....

Yeah, I don’t wanna get stabbed… 🔪😅