W113 Pagoda SL Group > Body, interior, paint, chrome, and cosmetic items
Fuel tank sender quirky?
Tom in seattle:
Before welding around the trunk I thought it may be wise to remove the fuel tank. So I drove around one afternoon to get the needle to show empty though the “E” light did not come on. I parked on an incline and started siphoning fuel into 2 gallon cans. At 5 1/2 cans (11 gal) it was finally empty. I’ve noticed that the car when low on gas (indicated) will usually hold only 7-8 gallons more. The sender unit appears recently renewed. What’s up with this thing?
Pawel66:
Tom, the sender and the gauge need to match - old type sender with old type gauge and new with new.
If the sender was replaced and changed from old to new and the gauge was not - the fuel level will be indicated wrong.
I am not sure if your car had old or new system originally, you can check it in the EPC. There is quite a lot in the Technical Manual about it and lots of posts.
Other topic may be (if your sender is new) to check the electrical connections. A check on sender and how it works may come handy if you have the tank out anyway.
WRe:
Hi,
just check the resistance values of the sender: tank full, floater up 4 Ohm, tank empty, floater down 83 Ohm.
...WRe
Tom in seattle:
Thanks all for your comments and help. My car qualifies clearly for the later model of sender. With that aside I pulled the sender out of the tank and put it to the resistance test. It measured 5 ohms at full and 65 at empty, not correct for proper feed to the gauge. As it is a tube style of sender I can’t really see action of the float but it seemed as though it’s travel was not the full length of the tube. But then I noticed that it was not a MB original part. It was a VDO branded sender. After some research I find that the 5 hole mounting scheme is a somewhat standardized mounting system for lots of tank senders. This one does not go clear to the bottom of the tank either, about an inch short. Looks like I’ll be buying a new one. The classic center had none but they are available on internet for about $180 (ouch) via Amazon.
scoot:
--- Quote from: Tom in seattle on May 16, 2019, 06:32:05 ---Thanks all for your comments and help. My car qualifies clearly for the later model of sender. With that aside I pulled the sender out of the tank and put it to the resistance test. It measured 5 ohms at full and 65 at empty, not correct for proper feed to the gauge. As it is a tube style of sender I can’t really see action of the float but it seemed as though it’s travel was not the full length of the tube. But then I noticed that it was not a MB original part. It was a VDO branded sender. After some research I find that the 5 hole mounting scheme is a somewhat standardized mounting system for lots of tank senders. This one does not go clear to the bottom of the tank either, about an inch short. Looks like I’ll be buying a new one. The classic center had none but they are available on internet for about $180 (ouch) via Amazon.
--- End quote ---
If it says VDO that's fine. It doesn't need to say MB on it. On the very bottom there is a plastic nut screwed into the center. Since you are going to replace the unit anyway you might as well try cleaning it first. Remove the nut on the bottom and you will see a small threaded shaft coming out. Next there is a disk on the bottom. It might just come off or it might sort of want to be unscrewed. Next is a plastic disk. Remove that. You should be left with a tube attached to the top of the unit. Wiggle that off and you should have the sender minus all of the tubing and bottom. Tip it right side up and upside down. Does it travel the whole length? If not, what is it hitting? Crud? Be careful not to damage the two thin wires that the float glides upon. Report back.
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