Anyone out there that knows how to reclabrate the fuel sending unit. I have taken out the tank and fuel sending unit and cleaned them both out.The sending unit looks like it's in good shape. It will register correctly down to about a little less than half tank and just set there. Luckly the reserve light still works so I know when to fill up. It just like you don't know how much diesel you have left until it's empty.What's so strange is before I cleaned out the tank and sending unit. The guage would show it going down all the way down. I had an alge prpblem in the tank and I knew that it was effecting the sending unit. I'm a little lost on how to correct the problem. Any advice would be appreciated. 1981 240d

You took the sending unit apart and cleaned the inside up good?

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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"

Yes The sending unit is spotless I checked th correct position of the little guides that go up and down the small wires also. The unit is clean and all parts look good.

When you had the FSU out did you verify the connections on the wires? there are two silver wires that the float has contacts on for determining the fuel level and a copper wire for the ground. If any of these wires were broken or not attached or even kinked, you won't get accurate readings. When I cleaned my FSU the ground wire was broken at the base and I needed to solder it with a new tab of copper.

The other thing to check is the center shaft that the float rides on. I cleaned mine with steel wool and an x-acto knife to make sure the float slid freely. You might have a bit of corrosion on that shaft making the float stick until the fuel level is low enough for it to drop from its own weight.

I know you said you cleaned it, but I don't believe there is any way to calibrate it. It either works or it doesn't. If it doesn't there must be bad contacts or corrosion.

If I'm wrong I'm sure someone will chime in.

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Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

Thanks for the reply. All the wires are straight and tight. When I had the unit out I cleaned the center rod too. I turned the unit upside down and right side up several times after reinstalling it back in the tube and I could here the float slidding up and down inside the tube.Guess it works freely enought. I'll check the contact soon as possible Didn't notice them being corroded though then may be.

Here's some notes I took when I worked on my 240D sender.

Fuel sender connector pinout:
T gnd, G sender, W reserve switch

float up 2.4 ohm G to T
float down 56 ohm G to T

float up W to T infinite ohms
float bottomed out W to T zero ohms

Take out your sender, put an ohmeter across G and T, tilt the sender to move the float slowly through its range up and down and make sure the resistance changes continuously up and down between 2.4 to 56 ohms with no dropouts. If it measures ok, the problem is likely elsewhere.

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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