'96 C280 Fuel Tank Sending Unit Replacement
 

Hello,
Can someone guide me on this please?
1) How do I remove the fuel sending unit from the tank? Does it unthread with a pin-wrench, or spanner wrench?
2) Do I have to drain the fuel tank to replace to replace the sending unit?

The sending unit is underneath the car, approximately below the floorboard behind the drivers seat. It is installed below the tank rather than on top of it. This is a bit of a concern to me, as I have replaced many seding units on other cars from the top.

Please help.

It's not really a DIY job. For starters, your car has two sending units. Replacing them is simple if you have the right tool (202-589-00-07-00), but special tools are needed to completely drain the fuel tank. Siphoning from the filler neck will only drain the passengers' side of the tank. You could drain the fuel from the rail by jumping the relay, but you may end up leaving some fuel on one side of the tank. I'm sure other members will disagree, but I'm overly cautious when dealing with gasoline. Of course, you could just run it out of fuel.

Thanks for the reply.
I dont have the shop manual for this car, therefore I didn't know it had two sensors. Is the other one located oppositly to the one on the drivers side also accessed by a plastic cover?
Does this car have two tanks that are connected somehow?
The problem is that the gage fluctuates, when 1/3 to 1/4 full, but works fine
from full on downward.

Thanks again for the information.

Look here for your fuel tank.http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=202028&M=104%2E941&GA=722%2E328722%2E424722%2E604722%2E605722%2E629&GM=717%2E441& CT=F&cat=44V&SID=47&SGR=015&SGN=01
Geo.:)

Thanks for the diagram, that explains it. Of course, not having the wiring diagram, how do you test to see which of the sensors is bad.
When I brigde the wire on the right side, the gage shows half full and empty when not bridged.
When I bridge the left side, it shows 3/4 full and empty when not bridged.
The scavenge pump on the right side seems to work as the car can be driven with less than 3 gallons in the tank.
Is there a test sequence for this?
Help is appreciated.

Just replace both of them. One has failed and the other is probably about to.
Dan

The problem is that the gage fluctuates, when 1/3 to 1/4 full,

This would suggest it is the first one you tested.
As " forp " mentioned, may not be a bad idea to replace both.
Had mine done about 2 years ago.
Apparently the newer versions have gold-plated contacts, and are not affected by " dirty " fuel. ;)

Well, I thought of replacing both also.
Let me check how much they are.

Thanks for all the help.