1996 C280 fuel gauge / sending unit

96 C280 (82,000 mi.) fuel gauge just started to dance all over the place from empty to full with any amount of fuel in the tank. The gauge mostly sits on empty and seeks a higher reading for several seconds and then returns to the empty reading. I have read of different fuel brands possibly causing this problem but believe I am going for the sending units. I see left and right listed w/ and without pump and wonder if the offered OEM or after market units are recommended as replacement for the MB parts. I am looking for proceedure for removal of the sending units as this is my first MB.
Thanks

[forp]

My '96 C280 has just developed the same intermittent problem. After searching the forums it appears that the fuel level sensors are the most likely culprit. However, when my fuel gauge "drops" to empty, the low fuel warning light does not come on. Does yours? With the needle on empty, shouldn't the low fuel light come on even if the information from the sensors is wrong? I'll see if the warning light still comes on normally when the fuel level is actually low (it does light up with the other panel lights when starting the engine) and the fuel gauge is acting normally. I would also appreciate info on replacing the sensors. Thanks

I still don’t believe it but running through 3 full tanks of fuel seems to have resolved the sending unit problem. Looking at my receipts my problem started following a fill up at Wal-Mart (10 % ethanol). I ran the tank low each subsequent time and filled up with 94 octane as usual at the local Mobil/ Exxon station. The gauge function became steadier with each fill-up and now it is rock steady.

[BenzBob]

As I have posted several times before, this has also been my experience and I attribute it to contamination in the fuel the makes the fuel sensing unit read inaccurately. I have used Exxon/Mobil, ETNA, Kangaroo and Hess gasolines with no problem. For some reason, BP causes inaccurate fuel gauge readings in both my 1995 C280 and 2000 ML320. Due to this reason have not used BP fuels in my vehicles for the last 3 years.

[sbourg]

"However, when my fuel gauge "drops" to empty, the low fuel warning light does not come on. Does yours? With the needle on empty, shouldn't the low fuel light come on even if the information from the sensors is wrong?"

If your sensor is similar in design to that in our 190E - no. The low fuel sensor is a closure switch on the float mechanism, and is triggered when the float hits bottom. The loss of fuel level reading corresponds to a sensor resistance of 'infinite Ohms' when poor contact occurs at the float wiper. Since 'empty' on the gauge is the highest resistance of the sensor, that is he end of the gauge the needle goes to when the sensor loses contact. The float is still where it should be.

Steve

[BenzBob]

Yes, when the fuel gauge drops to zero the low fuel warning light comes on after what appears to be a built in delay. I have never taken mine apart (1995 C280) so I do not know the mechanics of how it is designed.

[forp]

Well, after going through 2 tankfuls of gas other than Beacon, the fuel gauge is just fine. Thanks for all the help.

[BenzBob]

I am glad to hear that cleared up your problem without having to go through the trouble and expense of replacing the fuel sending unit.

The cause for this must be either contaminated fuel, some additive that some brands put in their fuel or possible the way some nozzles deliver the fuel to the tank. I really am not sure if I understand it, but on two of my MB's changing fuel has cleared up the problem just as in your case.

For anyone else out their who has this common problem with Mercedes fuel sending units, I would first try changing your brand of fuel and running 2-3 complete tankfulls through to see if your fuel gauge clears itself up. Sure beats spending the time/money in removing the fuel sending unit and cleaning/replacing it.