fuel gauge flakey

[P'bert]

Recently the fuel gauge and light on my 300D started to behave erratically, with the light flickering and the gauge zeroing in response to bumps in the road, or maybe bumps in the night. Now, the light is on always and the gauge shows empty, both of which are not correct. I disconnected the plug at the top of the tank and verified that the brown wire is a good ground, the blue/black turns the light when connected to brown, and the blue/green zeros the gauge when connected to brown.
Thus, I conclude that the sender in the tank is broken.

Questions: can it be repaired?
any of you have a spare for
sale?

Thanks,

Phil
'84 Euro 300D, stick shift and cloth seats

[Lycoming-8]

It is likely that the sender unit is just dirty, either from gummy deposits or algae. It can be carefully cleaned based on other postings in this forum. See the search capability of the forum(s) for other threads along this same issue.

[Motorhead]

Remove the first aid kit compartment. Remove the fuel sender. Carefully remove the outer cover on the sender by removing the small nut on the bottom. Ck to see if the wires are intact that the float slides on. Ck the contacts on the bottom as they are the ones that turn on the light. Ck the small holes on the outer cover of the sender. they can clog and not let the fuel flow into the sender. The contacts at the bottom are prone to deterioration from junk and water in the fuel. If not fixable, then you will have to replace the unit. Good luck

[lrg]

If the reserve light is on and the gauge reads empty then the contacts are probably good unless something wierd got in your sending unit and shorted. Algae won't cause a short. Given the tendancy to dive on bumps I'd guess the problem is as simple as a bad float. I once had one develop a slow leak and it gradually sank to the bottom and stayed there. As it filled up (it took a couple of weeks) all sorts of wierd things started to happen. If it is the float, it may be possible to repair it but even in the best of circumstances whatever sealant you use probably won't last long immersed in diesel fuel. You probably should just replace the sending unit. They aren't too bad pricewise. Check on the Fastlane site.

[P'bert]

Follow-up to my original post: I bought a replacement sending unit from a 230E in a wrecking yard. I dismantled it, cleaned the contacts, and marvelled at the clever design which the MB engineers had developed. When installed in the fuel tank, it worked great. On the other hand, the unit I removed from my fuel tank was indeed defective. One of the three wires, the one for the light, had broken, so that it could flip around freely, which explains the flashing lights and the very jumpy gauge. What might have caused the wire to break I cannot imagine. Is there a gremlin in the fuel tank? If so, he or she is a mighty filthy gremlin, since the removed sending unit was very very grungy. I'll be adding biocide to each tank for the next several tankfuls.

Phil