Fuel sensor gone bad?

[justinmm2]

Okay, I'd only been able to get 10 or 11 gallons in there before, but this is new. I drove to Target and parked with the needle just a hair under the quarter-tank mark. When I came back out and started the car, I immediately had the "Consider range on remaining fuel", orange light, and I'd never seen the gauge so low. I don't even think it moved when I started the car. OBC said my range was 9 miles.

When I filled it up (luckily I was a few hundred yards from a pump), I couldn't get more than 9.832 gallons in there, despite trying my darndest. I twisted that thing and re-inserted so many times. It just refused to take more than 9.832 G.

So what's the story? Do I have some sort of faulty sensor (why does that not sound like a cheap fix)? I know it's somewhat common to only be able to get ~11 gallons or so in there, but less than 10 and the immediate drop from 1/4th to 0/0th seems very strange. Would disconnecting my battery and reconnecting it with a full tank potentially fix the problem, or is it likely something deeper? I did some searching before I posted :)

Thanks for any and all insight,

Justin

P.S - Car is a 2001 911 Turbo, US.

Edited April 4, 2007 by JustinM

[Loren]

Would disconnecting my battery and reconnecting it with a full tank potentially fix the problem

Yes, that is a good place to start as it will force a minor re-calibration.

[justinmm2]

Would disconnecting my battery and reconnecting it with a full tank potentially fix the problem

Yes, that is a good place to start as it will force a minor re-calibration.

Loren,

Will do. My dad wonders if I have a "float" mechanism that older 911s do. I'm under the impression that this is *not* the case, and thus it probably isn't a simple adjustment.. could it be?

Thanks again,

Justin

[PTEC]

It does indeed have a fuel level sender "float" but due to the complex nature of the tank because of the 4WD system it also uses the instrument cluster to calculate fuel level when there is something like less than 3 gallons or something. There are no adjustments that can be made to the fuel level sender, however it is a fairly common failure, especially in earlier cars. You can really only test it when its removed. You would do so by hooking up an ohmmeter to it and moving the float up and down. When they're bad you will see dead spots in the rheostat that measures the movement of the float or the resistance wont read consistently or smoothly during movements. If this is the case, you'll need a new sending unit as the rheostat can not be serviced independently of the entire assembly.