I have been the proud owner of a 1980 300SD for nearly two years. In all that time, the low-fuel indicator lamp has never worked. I've searched the topic, here, and have intended to check the sending unit when the weather gets better. Yesterday morning, VOILA, the indicator lit up for the first time. My needle was a good 1/8" above the "R" on the guage.

About two months ago, I actually ran out of fuel with the needle in about the same position, so I am sensitive to the fuel level.

It seems I have two problems: the fuel guage doesn't accurately represent how much fuel is in the tank, and, now, the low-fuel light has "fixed" itself. Life is not this simple.

Any ideas why this is happening, and what would you veterans suggest I do to improve the credibility of my fuel guage?

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1980 300SD 146K miles.

Get a new tank sending unit. Both the gauge reading and the warning light are activated from there.

Diesels accumulate algae in their tanks and it often causes your problem with the sender. In a gas car it would have simply wore out by this time.

Replacement is simple. Remove the first aid kit from the rear shelf and the sensor is right there.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician