Sounds like your fuel sending unit. Sometimes they get dirty or just need replacing.

I'm not sure how to access it in a 124. I'm sure though someone will chime in with the proper info. Until then, you might remove the tray that holds the first aid kit and look under there,(that's where it is on a 123). There is an electrical plug that fits into a big (44mm) hex cap. Unplug it and unscrew the cap. Carefully withdraw the cap, (the sending unit is attatched), wait for fuel to stop dripping, use a rag to catch any drips and withdraw the sending unit.

You can use parts cleaner to remove any crud. There are very thin and delicate wires that run the length of the sending unit. If they are broken, a new one is probably needed.

Good luck

__________________
Mr. BILL

91 300E 120K
90 300SE 275K (sold)
92 BMW 525iM 120K
90 BMW 525iA 175K
85 300D 175K (sold)
84 300SD 245K (sold)