Fuel Sender / Gauge
 

Is there ANY way to bring some accuracy to the Fuel Indicator!? If there's one thing about my car that annoys the hell out of my is my phantom quarter tank of fuel.

I had this problem sometime after installing a NEW sender unit. to ascertain if it was sticking i removed and cleaned the delicate resistence wires and the guide rod ,sprayed ly with a silicone based lubricant and all is well. i assume there is accumulated moisture in the fuel tank causing micro rusting. in my 111 i simply added some ATF to fuel and it worked
mak
300se 103

Yes - cleaning the sender unit can help.

Fuel gauges are non-linear due to them being resistance measuring analog devices. as in analog voltmeter.
(how's that for fancy BS?)

cleaning is all you can do, even in the best case , I dont think they are very accurate , the mechanism design limits it being precise

Out of curriosity can someone tell me the socket size to remove the fuel sender from a W123 wagon?

I cleaned mine and nothing changed. Even though everyone said the sending unit was the issue. Granted its been proven it can be. So of course start there. But it not, remove the gauge cluster.

Easy to do, just search for directions. Once you get down to the fuel cluster and its removed you may see some resistors and a potentiometer (small dial). At least this is how it is in my 91 560SEL. After soldering EVERY part of the cluster I have gone back and just done the resistors and the pot again. Every time I solder it gets better.

But I think the pot and resistors are shot. If I look at the uncoated side of the board it looks baked. Others have noted that also. Also the gauge may be more accurate when just starting out then as things get warm the gauge may jump up to a higher level. So since I can no longer get it any better, next step is to replace them.

But one thing was clear, cleaning the sending unit did nothing and soldering the cluster did lots. So logic would say that sometimes its the cluster. After all, re-soldering stuff work very well for most VDO stuff it seems.