Hi all. I have been down the rabbit hole with Mopar fuel tank sending units for many years now. I have tried all the tricks with the poorly made linear reproduction units with new used and restored gauges. And even tried the meter match on the last car I did. Worked but not fully satisfied with it as it still works in a linear style. I have a 34K 70 Cuda that I am doing and getting things ready while it’s in body shop jail. I’m down to the fuel sending unit for the fuel system and removed from the tank and the original unit is corroded so I let it sit outside for a few days to get rid of the bad gas smell. Ohm tested it this morning and surprise it works not great and smooth but it works. So I am going to try something different and either overhaul rebuild or totally screw it all up. I have never had an original one apart but know that the originals are elliptical do to the shape of the tanks. I bent the tabs over and opened it up and the wafer board resistor and reading leg looks nice for 50+ years old but the metal and rivets not so good. Not sure how I am going to disassemble totally or even if I want to but gonna try before I accept defeat. I will keep it updated on my progress if anyone is interested. Also please share any info if anyone has tried this. It would be greatly appreciated. Don’t know why pics show sideways. Thanks
Going to try repair my fuel tank sending unit we will see how it goes
- Thread starter Sedbld
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BLK 68 R/T
Well-Known Member
Soak it in evaporust. Or maybe a low pressure bead blast.
You have a lot of corrosion there - and it looks to be between the contact rivet and the shell of the resistor - giving potentially the bad connection that is causing all your problems.
Geoff 2
Well-Known Member
Do not agree that the rheostat is in good shape. It has come away from the support plate & may give erroneous readings. Looks like corrosion on the support plate has built up & forced the rheostat away from it. I would buy a new sender. You hear reports about bad senders but most just need adjusting.
BLK 68 R/T
Well-Known Member
You can’t just adjust them and make them right. Can get them somewhat close but not accurate.
BLK 68 R/T
Well-Known Member
The new sensors are just flat out not made correctly. I have heard of an accurate reproduction one being made now, I’m assuming with a correct rheostat? The issues with them not reading correctly has been well documented for many years. No matter how you bend them they will never read the fuel level correctly. Like I said they can be close, but not accurate.
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how hard can if be to duplicate 75 year old technology? 
Geoff 2
Well-Known Member
It is not hard, it is being done everyday; it is a very simple device: a wire wound resistor with a wiper arm. You cannot get that wrong if installed correctly. This assumes the resistance is correct.
Roadhog51
Active Member
I just went through this with my 69 RR. The car had a new sending unit and new gauges when it was restored in 2019 and the FG would only go to 1/2 tank when full. I did the ground the wire trick and the gauge went to full. I tried to take apart the "new" sender, and it literally fell apart in my hands so I ordered a new one. I checked it with an ohm meter, and it tested correctly, I installed it and I will only go tank 1/2 tank too!!!!!! Now I am told that the Ohms on the new senders are not compatible with the ohms on the new gauges DUHHHH!!! Why make something that doesn't work???? DUUUHHHH!!!!
BLK 68 R/T
Well-Known Member
You can bend them 6 ways from Sunday and they will only be correct part of the time. The problem is the rheostat on the new ones is not the same as the old ones. So as mentioned above, the ohm reading is not correct.
The original design of the sender and shape of the tank were a mismatch made in heaven from Day One.
These senders will never read accurately on the gauge no matter what and how much they are tweaked. The best a guy can do is get used to where the needle sits as to how much gas is left in the tank.
And typing is bold only highlights your non-understanding of that.
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