85 FB

Okay, I'm starting to despise my 7 right now. (It's one of those Love-Hate relationships with these cars.) As some of you know, I just finished replacing my old tank with a refurbished one and a brand new sending unit from the dealer.

I now have a new problem: I just got a full tank of gas today (and I made sure it was a full tank). However, my needle reads just below the 3/4 Full mark. What gives? My old sending unit on a full tank read just a bit under the Full mark (in between 3/4 and Full). Is this one of those deals where the tank has to go from full to empty a couple times for the sending unit to recalibrate itself?

Or, is it a bad connection? I know my connections are good (however, I did get a replacement pigtail connector for the sending unit if it needs to be). I'm really starting to question my ability to effectively work on my 7, or trust the parts that I install.

Rogue_Wulff

The connections could be part of the issue. You may have a faulty gauge as well, since it didn't read 100% accurate before.

85 FB

Well, when I first bought the car in '05, and I would get a full tank of gas, the needle would read Full. Only after a good long time of use, would the needle not read Full, just a bit below it. And, when I replaced the gas tank and removed the stock wiring, there was a lot of corrosion on one of the prongs for the sending unit. That might've been the reason for the gauge not reading all the way at the Full mark.


Let's say it's the gauge. Could I easily replace it with an Auto Meter fuel gauge? I don't know if the Ohm reading with the stock setup works with an aftermarket and whatnot, this is completely new territory to me.

Rogue_Wulff

Start with checking and cleaning the connections. It doesn't take much corrosion or looseness in them to mess up the readings. I simply threw in the possibility of the gauge being faulty, because you had siad it wasn't 100% accurate before.
As for an aftermarket gauge, I can't answer that question with any certainty. I'm sure there is a way to do this, but it may require a sender to match the new gauge.

DavidMyers53

If it's a new sending unit, the float arm that goes up & down may have to be adjusted...

I installed a new one, and fortunately, it was fairly accurate out of the box.

- David

darkfrost

iTrader: (1)

Yep, you need to bend the float arm and measure the resistance.

3 ohms at full, and 110 ohms at empty (from memory)

85 FB

I do remember reading the Ohms requirement in the FSM. Thankfully, all I have to do is remove the left rear wheel and dust panel to gain access to the sending unit. I'll see if I can borrow my friend's multimeter.

The connections are all new, no corrosion because I had to use brand new female connectors on the new sending unit.

I know the fuel sending unit has stopper tabs on it for empty and full. I take it I would have to bend the arm to where it wouldn't be stopped by those tabs as easily? I could've sworn, tho, that when I compared both fuel sending unit arms, they were identical. Could it be that even tho they look identical, one could be off?