Fuel tank never accepts the full 17 gallon capacity

My fuel gauge never shows more than 7/8th full at full-up. Once last week, I was on empty (fuel light on for days), I actually ran out of gas. However, I could not fill the tank past 15 gallons. Even when the light first comes on, I usually can only get 13 or 14 gallons into the tank.

I read under one of the stickies that it�s due to the newer vapor recovery nozzles. You can defeat it by turning the nozzle 180degrees (so handle is up) until the auto shutoff click.

Quotes source post: 19037368

I think I�ve tried that, but it�s been awhile, and I�ll try it again. I think I hear the fuel actually getting up to near where the filler is when the shutoff occurs.

Here is a link to a thread on the same topic. https://rennlist.com/forums/996-turb...k-of-fuel.html

Someone has hidden gold bars inside your fuel tank, displacing the last bit of space for gasoline?

Quotes source post: 19037350

Had the same problem on my 02 996. Had to adjust the sender unit. Done a lot of work with the evap/venting systems on a 01 & 02 996. after much research, thinking and hands on parts changing, have got a good grasp on the fuel tank systems of c2. If your tank only fills to 1/2-3/4 on the gauge its a venting problem more than likely. If it fills to 7/8, its a sender unit problem or a bad calibration of sending unit. Fill tank as full as reasonably possible. Take the battery out, battery tray out, unscrew the tank hat retainer ring, and remove the tank hat with the sender unit. Detach any hoses/wires as needed to get the sender unit out. With the tank hat out its easy to see the fuel level in your tank. Look, see how full it really is. If there is room to fill it more, do it with a gas can thru the tank hat port till the tank is full. Put the sender unit temporarily back in and plug in sender unit. Turn the key to the first notch that lets the gas gauge work. See if the gauge now reads full. If it does read full its a fill pipe/venting problem, although these type of problems usually only let tank fill to 1/2 -3/4 full max so its doubtful it will read full. If it still reads 7/8, but the tank is full to the top when looking in thru the tank hat port then you have a sender unit has a problem. Many techs when changing the fuel pump brutalize the sender unit float assembly. Its very sensitive, a small bend can easily change the gauge level it reports. A dead area on the sender unit rheostat can also be a problem. With the sender unit out but still plugged in and key on to let gauge work, manipulate the float up all the way and down all the way while someone watches the gauge for full movement. If the gauge does not read full when float is all the way up the rheostat is faulty. Try to clean it off with some brake clean, very very lightly sand/brush the rheostat coil wires and contact on float arm, don't go nuts here. When checking gauge might want to give it some time to 'normalize. You'll be able to see how it reacts when manipulating the sender manually and looking at the gauge to see its reaction time... If above cures your problem, great. But more than likely the float shaft rod got bent when pump was changed out. So now you can gently bend the rod down very slightly and re-check fuel tank level on gauge. Don't go over board here, if you bend the float rod to much the opposite problem you'll have and the tank will read full when its not. So go a little at time till it just reads full with the tank topped off all the way. jmo

The above post by Allcool has a lot of good common sense stuff in it about fixing an inaccurate fuel gauge. With the proper Electronic diagnostic/repair tool you can also calibrate the fuel gauge...Empty the fuel tank, then add the exact quantity of fuel (5 gal?) then run the calibration program in the Software..