fuel gauge issues
 

my 79 240d fuel gauge worked great when I drug the car home.

I removed the tank and cleaned everything out. But ever since the gauge doesn't work.

I removed the sender cylindar again and cleaned it very well with brake parts cleaner. I made sure to get lots of the solvant inside the cyl so it could brake up the gunk inside.

When I put it back in the gauge lifted from the dead bottom to the 'R' - still showing empty. The tank is full - or nearly so - I just filled it up.

What are the common trouble shooting things I need to look at? Is there a ground I forgot I removed?

did the cleaner kill the sender?

I did a search and found the link.

When I cleaned it - I didn't know I could pull the cyl apart and clean it from there. I will do that tonight & see if I have it back online.

Did you take it apart as shown here?

http://www.peachparts.com/Wikka/W123FuelSender

Or did you just dip it in a tub of brake cleaner?

When I took mine apart I found there was loads of gunk in there that would in no way be shifted by brake cleaner through the little holes...

http://www.peachparts.com/shopforum/diesel-discussion/277167-w123-300d-fuel-tank-sender-question-2.html

http://www.peachparts.com/shopforum/...pictureid=2349

http://www.peachparts.com/shopforum/...pictureid=2351

But that is nothing compared with post #22 in the same thread!

Ha you beat me to it!

That's because I'm as fast as my 240D!

the thin wires break, or the slider malfunctions, difficult to fix, if you have some nichrome wire you can try, mine worked after my fix but only so so

I got it apart. 1 of the 3 wires is broken. But it isnt one of the two the float rides on. The rod the float slides up and down is/was very nasty and rusty. It took quite a bit of emery paper to get it cleaned. The float does slide easily up and down now.

I re-installed and it goes to about 1/3 tank. I'm hoping it will go down as the fuel level goes below 1/3. If it is accurate for that last third I'll probably leave it.

If not - I'll order a new one.

Ummm sorry to bring bad news - they're not cheap - about 300 euros last time I looked I think. Look for a second hand one.

ouch! - I will be trying to repair the wire in this one then. It doesn't look that hard. Solder a new strand in at the top and wrap it around the bottom & repeat. Of course it alwasy sounds easier than it really is.

I believe the third wire is for the low light, not the fuel level.

I'd recommend doing a search for a pick-n-pull; or post on the parts forum for a WTB.

as mentioned not any wire will do
look here
http://www.peachparts.com/shopforum/vintage-mercedes-forum/136823-anyone-ever-rebuild-gas-gauge-sending-unit-w114-w115.html

interesting - I had thought about pulling a strand of wire from an old cord or somthing. But if its just the low fuel light - I'm golden. so long as the gauge reads the bottom 1/3 of the tank.

I would prefer it float to the top - but beggers cant be choosers.

The service manual says the gauge/cluster design changed in '82 to include a test of the low light function in position I of the ignition.

If your low light doesn't light up at all, that might mean it's above the limit, or might mean the wire's broken. Later clusters would show the light on start up.

If you get a reading, then the float might be okay. Having a two gallon fuel can in the trunk might be prudent though.