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Fuel level sending unit question
My low fuel level light only comes on when the tank goes completely empty. Furthermore, once I get down to about 8 gallons in the tank, the fuel level gauge goes down to R and stays there forever. From what I found out from searches and from my own suspicion, this means my fuel level sending unit is messed up right? Just wanted to get the opinions of techs or people who have gone through this before I purchase a new sending unit and start the replacement task. Thanks. Oh, car is the '84 300SD.
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1999 Mercedes-Benz S600, 103K miles - garage queen 1988 Mercedes-Benz 560SEL, 89K miles - daily driver 2007 Hyundai Sonata Limited, 31K - daily driver |
#2
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Also I forgot to mention that my temperature gauge isn't working properly. I already changed the sending unit but it still flickers sometimes. Now that I think of it, the temperature and fuel level gauges are on the same part of the instrument panel. Maybe that is really messed up.
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1999 Mercedes-Benz S600, 103K miles - garage queen 1988 Mercedes-Benz 560SEL, 89K miles - daily driver 2007 Hyundai Sonata Limited, 31K - daily driver |
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Some considerations
This post is based on my W123 work, I dont' have a 126 manual anymore since the 300SDL is gone. So minor variations may exist. Someone with a 126 will correct me if I'm wrong, I'm sure. I played with the fuel sending unit on my daughters 240D. The lack of a correct indication could be due to algae/crud on the sending unit wires. Remove the unit and open it up. Clean it with carb cleaner. It will take 2-3 cans of carb cleaner. Removing the sending unit. http://www.peachparts.com/shopforum/showthread.php?t=102003&highlight=fuel+sending+unit Then open the sending unit by unscrewing the nut at the bottom. Slide the tube off the assembly. Be careful not to damage the 2 wires. Clean the unit completely with carb cleaner. Check the resistance at the plug with an ohm meter while sliding the float up and down, this will make sure your unit is making contact. Also check the reserve light contact. Reassemble and install with a new Oring. Here is the SM for the W123 http://skinnerbox.steaky.org/Service/W123/Index/617T/47FuelSystem.htm Also the reserve light goes thru the seatbelt warning relay. My daughters light did not work. I replaced the seatbelt relay and it now works. Test the light first. Test the reserve contact in the sending unit. If they both check OK then it could be the seatbelt relay. These proceedures shold be covered in the Service Manual. Dave
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1970 220D, owned 1980-1990 1980 240D, owned 1990-1992 1982 300TD, owned 1992-1993 1986 300SDL, owned 1993-2004 1999 E300, owned 1999-2003 1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD 1988 560SL, 100,000mi, owned since 1995 1965 Mustang Fastback Mileage Unknown(My sons) 1983 240D, 176,000mi (My daughers) owned since 2004 2007 Honda Accord EX-L I4 auto, the new daily driver 1985 300D 264,000mi Son's new daily driver.(sold) 2008 Hyundai Tiberon. Daughters new car |
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My 240D didn't have a nut at the bottom of the sender so I could take it apart, I may pull it in a day or two and look at it closer. All I did when I had it out in the spring was spray carb cleaner into the holes and let it drain.
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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride. '13 Chrysler 200 Touring Candy Red. Grandma's ride. Age and cunning will always over come youth and vigor. |
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Quote:
Dan |
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I had a similar problem with the gauges on my 300sd. Started of the fuel gauge didn't meaures the fuel in the tank properly. Learned a whole lot from dissassembling and reassembling various clusters. Now, five clusters later, I have a fully functional unit. I have 2 or 3 300sd gauge clusters laying around at the house, but can't remeber which one's have good gauges, and which ones have bad gauges. If it comes down to it you should be able to buy a whole entire cluster for less than 100 dollars. Check ebay, user id usedpartshunter, that is who I got mine from. If you have access to a gasoline speedometer though, you might be able to make it work to an acceptable degree. Of course the diesel units don't have the economy gauge, but other than that, the oil, temp, fuel gauges are virtually the same. You would though have to get a wiring diargram of the cluster and rearrange the pins to match the gasoline's board arrangement. Probably eaisier just to get another one though.
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Quote:
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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride. '13 Chrysler 200 Touring Candy Red. Grandma's ride. Age and cunning will always over come youth and vigor. |
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The carb clean works magic..
I ran a bunch through mine and it seems to be ok now a lot smoother Why does my 300SD w126 only seem to have a 18 gallon tank? I looked it up and it is supposed to be more? |
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related (W123) fuel level sending unit question
Hello,
My low fuel warning light started to come on dimly this week, with more than half a tank of fuel (240D). When I topped off the tank, the light went out for a few miles. Then it came back on. Today, I replaced the voltage regulator to no avail, and checked the fuel level sending unit, but I did not get the fastener off the bottom, so I did not inspect the wires. It seemed like some black crud was coming out the top holes when I held it upside down. Is this probably a sending unit issue? I only replaced it seven years ago when I got the car because it was not working at all at that time. Price of a new unit must be over $100 by now. Don't want to spend it if I don't have to. BTW, this 240D now has 353,576 miles.
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- Jeff 1957 W121 190 (history) 1966 W108 250S 1967 W108 250S (parts) 1982 W123 240D (history) 1989 W124 260E |
#10
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Quote:
__________________
'10 Chrysler T&C Stow-N-Go White. Grandpa's ride. '13 Chrysler 200 Touring Candy Red. Grandma's ride. Age and cunning will always over come youth and vigor. |
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That little nut on the bottom of the sender has something like a tight fitting little "round" of plastic tubing surrounding it. I just preyed if off, undid the nut, fixed the sender and used thread lock on the nut when reassembling.
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1985 Euro 240D 5 spd 140K 1979 240D 5 spd, 40K on engine rebuild 1994 Dodge/Cummins, 5 spd, 121K 1964 Allice Chalmers D15 tractor 2014 Kubota L3800 tractor 1964 VW bug "Lifes too short to drive a boring car" |
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Come to think of it I think I did finally get the nut off, because I did eventually get it apart, just been so long I forgot. My memory is not what it use to be to say the least.
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'10 Chrysler T&C Stow-N-Go White. Grandpa's ride. '13 Chrysler 200 Touring Candy Red. Grandma's ride. Age and cunning will always over come youth and vigor. |
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LOL, Yah me too...what were we talking about?
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1985 Euro 240D 5 spd 140K 1979 240D 5 spd, 40K on engine rebuild 1994 Dodge/Cummins, 5 spd, 121K 1964 Allice Chalmers D15 tractor 2014 Kubota L3800 tractor 1964 VW bug "Lifes too short to drive a boring car" |
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I figured if I started prying that little plastic tubing off, that would be the end of the sending unit but I could bring the unit into the shop tomorrow and attempt it.
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- Jeff 1957 W121 190 (history) 1966 W108 250S 1967 W108 250S (parts) 1982 W123 240D (history) 1989 W124 260E |
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I got into one where the little wire was broken at the bottom. A friend held it and I soldered it back together. I tucked it away for a spare and didn't try it, but I think its fixed
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1985 Euro 240D 5 spd 140K 1979 240D 5 spd, 40K on engine rebuild 1994 Dodge/Cummins, 5 spd, 121K 1964 Allice Chalmers D15 tractor 2014 Kubota L3800 tractor 1964 VW bug "Lifes too short to drive a boring car" |
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