raschemmel:
You have not given the Fuel Sender unit output voltage yet, only the supply voltage. When you post the Fuel Sender unit Output voltage we can talk about how to condition that for arduino analog input. Not knowing what that voltage is I could only give you a vague and general answer , such as , use a voltage devider and an op amp. There, that was helpful , wasn't it ?
I understand.
The fuel sensor operates on the same voltage as does the rest of the car system. So the fuel sender/sensor's output voltage varies with the resistance it's creating. It is typical float-type sensor. When the fuel is empty, resistance is 3 ohms and when full it's 110 ohms. Hope it made it more clear.
Also, needless to say that English is not my native language 