My 1981 300 SD has had a very erratic fuel guage needle since I purchased the car, and it has been getting worse. It was pretty accurate below half a tank, but between half and full it would bounce all over the place.

Today I removed the sending unit and disassembled it to clean it. There was a fair amount of junk inside the tube. I also found one of the three wires to be loose at the bottom, not connected to anything. For lack of a better description, it was the middle wire that is slightly thicker and appears to be copper as oppossed to the thinner steel looking wires that are attached to the float.

There is a tab that the copper wire had appeared to be soldered to at one time, so I re-soldered the wire there.

Now the fuel guage needle rises a little less than 1/4" when the car is started. That's it, and the tank is half full.

What did I do wrong and can I rectify the situation?

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend

Is the float moving freely? Maybe its still stuck at the bottom?

Theyr'e fairly precise instruments, a lot of the time they can't be repaired, and you just have to buy a new one.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Pull it out again and make sure the wire are in the proper place on the float. There should be two copper tabs that the wire sits in between, if they are not in the proper place the float has a hard time moving up and down.

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Thanks guys. I guess I'll pull it back out tomorrow to assess how well the float moves.

Just a little discouraging to go from bad to worse despite my best efforts

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Pictures of the MB: http://s230.photobucket.com/albums/ee41/EricandRobyn/1981%20Mercedes/

1981 300 SD with a Goldenrod water block and Injetor line heaters. EGR is missing

1999 F-350 with HP X-over, Dahl 100 Fuel Filter, Coolant by-pass filter, CCV mod, Tymar intake.

Both on single tank WVO blend

i'd bet that a bone yard would have one that would work.

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-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto