97 E420, 80K miles... fuel gauge always reads full following renewal of the level sender. (The original sender was damaged by fuel with a high sulfur level.) Prior to sender replacement the gauge would read full at engine startup and then fall to a lower level during the drive. Now the gauge constantly indicates full; the low level warning light is functional during engine startup.

With the sender's leads disconnected the fuel gauge reads 1/4. Connected the leads to a second, new sender and manually moved the float... still the gauge reads full, regardless of the float arm's position.

Is this an instrument cluster problem??