The gauge sender is often glommed up after years of crud in the tank. It’s an easy fix that I’ve written up several times. You can do this with a pair of big channelocks, you don’t have to have a 36mm socket.
Here’s the archive of it: https://web.archive.org/web/20020311143203/http://www.mbz.org/info/articles/fuel_system/fuelsender.html Ful text: Tools Needed: 36mm Socket 8mm socket or wrench to remove seat back bolts Lots of clean shop towels or rags. Plenty of room around car for seat bottom and back to clear doors while removing. Fuel tank as low as you dare to go with it. Procedure: 1.) On a 126 and some 123 chassis cars: Remove rear seat bottom by releasing 2 red clips on forward bottom edge of seat frame. Pull to one side on the clips while lifting up - you'll feel the seat frame come up as soon as they release. Lift up on the forward part of the seat bottom and pull towards the front of the car. Carefully remove seat bottom from car. On most 123 chassis cars the sender can be accessed through the first aid kit box on the parcel shelf. Check your car before yanking anything out! 2.) In the center of the seat back below the armrest is an 8mm screw. Remove it. On either side at the lower corners of the seat back are metal brackets with 8mm screws in them. Remove these as well. Climb into the center of the back seat area and lift the seat back straight up. There's a metal lip on the back of the seat that hooks on two "ridges" just below the parcel shelf. Lift the seat back off of these and carefully set it down in the back of the car. CAUTION: Use two people for the next step!! 3.) With another person's help lift the seat back and remove it from the car. Why two people? Because if you try to do this yourself the seatback is too heavy. You'll end up dragging one of the corner brackets across the top of the wheel well or somewhere else around the door area. I have the scars to show for it. Now is a good time to apply some Leatherique to the seat back and bottom while you have the whole thing out. 4.) After wading through the spare change, candy, Cheetos, etc, you'll find some black insulating/sound deadening material draped down the back of the seating area. On the left rear (driver's side) there will be a cut-out just below the parcel shelf. Carefully pull this portion back. underneath is a large (3"-4") diameter plastic plug. Pry it out of the opening it seals. 5.) You are now looking at the top of the guage sender. Carefully remove the electrical connector and move it out of the way. Place your socket on top of the sender and turn it counterclockwise. Once unscrewed all the way, get ready with some shop rags/towels. 6.) Carefully and SLOWLY lift the sender assembly out of the hole. As you lift, fuel will be draining out of the cylinder. There are two holes in the side, one near the top, another near the bottom, with still a third in the base. Look down into the tank as you get close to the bottom of the sender or listen carefully to tell when the fuel has stopped draining from the sender. Have some towels or rags ready, as when you remove the sender from teh tank there will still be fuel dripping from it. Be patient! Too many of us have pulled the sender out prematurely and gotten baptized with #2 diesel. Yuck! Take the sender to a clean work area where you can disassemble it and lay the parts out. 7.) Start by wiping the outside of the sender with a clean towel. You'll be amazed at the nasty black stuff all over. get used to it -you're going to see more . . . On the bottom of the cylinder is a small round "nut". Carefully unscrew this with a pair of pliers and put it aside. Gently twist on the bottom of the sender and it will start to come apart. Be prepared for more fuel! Here's what you will find: A.) Flat metal disc that covers the bottom of the plastic plate and acts as the "floor" for the maze. B.) Plastic disc that is the closure plate for the bottom. Lots of convoluted grooves in it, like a little maze. Make sure these are cleaned out, as they act as a damper for fuel to flow in and out of the sender cylinder. C.) Outer tube of the sender. Two small holes in the side, both should be open and unclogged. These allow fuel to flow in and out of the sender so the float will register properly. The inside will be messy as well. Clean it. I pass paper towels (or better yet, a non-fuzzy shop rag) through it. D.) Sender float and guide rod/wires. Here's where the fun begins 8.) Clean all the individual pieces, saving the float/guide rod assembly for last. You can use any number of solvents for this, just use them in accordance with proper safety practices. My cleaner of choice is an electrical contact cleaner. 9.) Take the float/guide rod assembly and carefully clean it, using a cotton swab or something appropriate. Handle it carefully, as the fine copper wires on the sides are very important as you will discover! On the bottom is a disk that lines up with two copper "arms" on the float. This is your low fuel light circuit. Make sure the contact on both the float and the disk are clean. You can burnish them with some emery cloth if necessary, as they will probably be pretty nasty. I like to use electrical contact cleaner to clean the low fuel contacts as well as the wipers and wires on the float. 10.) You may find one of the fine copper wires is broken, which will account for no low fuel light. If this is the case you can resolder the wire using a low wattage soldering iron and the correct solder (60-40 electronic solder form someplace like Radio Shack.) It has been my experience that the wires typically break at the connection point where the original solder joint was, so no patching is necessary. If a wire is broken plan on replacing the sender. They are made of nichrome (I believe) and are an integral part of the resistance chain for the sender circuit. 11.) Now that you're done, carefully reassemble the pieces, paying close attention to the placement of the plastic end cap and metal disk. Once you have the sender reassembled don't place it in the tank - plug it into the harness and use a jumper clip (wire with alligator clips on both ends) to ground it. Turn on your ignition to see if you have your low fuel level light lit. 12.) After this test, remove the connector, carefully replace the sender in the tank, remembering to put the sealing ring on it, and tighten with the socket. No need for brute force here, just make sure the sealing ring is slightly compressed. 13.) Replace rear seat and related goodies 14.) Get a cold beverage of your choice and enjoy a snack from the remnants that lie under the rear seat! Ahh! Life is good! -D > On Jan 24, 2021, at 5:51 PM, Donald Snook via Mercedes > <mercedes@okiebenz.com> wrote: > > I did a diesel purge with the kit from Kent (Mercedes Source). It worked very > well. I thought. At first, it was spewing out a lot of white smoke. About > halfway through it smoothed out and had no smoke. None. > > I took it on a drive. It is still a little slow. I’m thinking valves are out > of adjustment or the linkage is too loose. > > When I got back I parked it in front of my house and moved my truck. When I > went back to start the car, it was a little hard to start despite being warm > after drive on highway. It is 50 degrees here. So, it’s not exactly cold. > When it started it blew out LOTS of whitish smoke. I mean lots! I have not > changed fuel filter yet. > > The reserve light was on when I got from Kaleb even though it had 1/2 tank. > It went out when I filled it up. But, it came on again with 3/4 tank. I > drove another 100 miles and the light was on with half tank. So, I guess the > sender is all > Gummed up. Could that also mean the sock in the tank is all clogged up? How > do you get that out without dropping the tank? > > Donald H. Snook > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
