Fuel gauge pegs at max repeatedly while driving - early style

[scoot]

I'm having a little trouble with my 1962 220 Sb, which is the same fuel sender and gauge logic as an EARLY 230 SL has.  After cleaning everything my sender unit now works correctly.  However when driving around the fuel gauge goes up and down 1/4 tank which I accept as normal for this type of sender unit, however it also PINGS up to max every so often, sometimes frequently.  I want to think that this is a bad ground issue, but not sure.   Have others encountered this before with the EARLY sender or gauge setup?

thanks
Scott

[ja17]

Hello Scoot,

This is usually caused by a worn place on the coil of the sending unit. I had a car that would start pegging after it got below a 1/4 of a tank. I don't think this is easily fixed.

[GGR]

I have the same issue on my '62 W111 Coupe, below 1/4 of a tank. I have tried to modify the shape of the coil assuming contact was bad, clean it etc. to no avail. If someone knows of a fix, I'm also interested. 

[scoot]

I'm getting the impression that it isn't making good contact at the plug.  When I move it around on the plug, it stops doing it.  I think I need to dismantle the plug and tighten the contacts a little...

[scoot]

I'm not having much success.  Is there a replacement fuel sender available from some other car that works?  I believe the original to be NLA.

[jpinet]

I see them once in a while on ebay, but Pelican parts sells new ones, original MB for 288$
http://www.pelicanparts.com/catalog/SuperCat/W113/MBZ_W113_FULFUL_pg2.htm

Not cheap, but better than running on empty!

Best,

JP

[scoot]

I see them once in a while on ebay, but Pelican parts sells new ones, original MB for 288$
http://www.pelicanparts.com/catalog/SuperCat/W113/MBZ_W113_FULFUL_pg2.htm

Not cheap, but better than running on empty!

Best,

JP

That's the later tube-style sender, and at a rather dreadful price.  On-line MB for under $200 is available.  Wow.  Those have really gone up in price.  1105421204 is the tube-style sender.  I have 1115421104 which shows as being available from MB online, MSRP $244, on-line $182.  That should be the same sender in a very early 230 SL also... 

[Sept]

I have a '71 280 SL.  After filling the fuel tank the dash gauge goes to full..within 20-40 miles it drops to 2/4 and within 80-100 miles it's down to  just above R.  Filling the car only requires about 1/2 capacity of the tank so I believe there is a problem with the float or sending unit.  Has anyone else seen a similar problem? From what I see here a sender is rather expensive if that's the problem.

[garymand]

The sending unit sensor is a little complicated.  Running the length of the tube, inside the tube are 2 thin straight parallel wires.  A float rises and falls straight up and down following these two wires.  The wires run through two holes on either side of the float.  There are two contacts in the float that short the wires resulting a linear travel, variable resistor sender.  As the float goes up and down the resistance changes.  I don't understand why it would give a full signal without being up at the top of the wires.  Try an ohm meter.

These things are notorious for iratic movements usually just from the slide contacts on the wires.   I took mine out and apart once and that was easy.  The scary part is is touching those thin wires with thick stubby fingers.  All you can do is connect an ohm meter and run the float along the wires looking for where the problem repeats.  That points to a wire contact issue.  If it doesn't repeat at the same place that indicates loos contacts.  I put mine back together with not much change.  After sitting for 10 years with a lot of gas in the tank, it is working fine now.