Fuel Guage
 

When I fill up 2004 boxster, it goes to full. But it never goes below a half tank. I just go about 300 miles and fill it up. Any idea what would cause this? Thanks

Could be a real life miracle and you're living right?

Sounds like the float is hung up on a wire inside the fuel tank. Pretty simple job to do to untangle it.

I made this mistake once when I replaced my fuel level sending unit. I was stuck a mile from home with an empty tank and a 1/4 showing on the fuel gauge!

Mine does the opposite. It only goes up to the halfway point. however, it is accurate once it goes below that.

If the battery is disconnected with the fuel level below 1/4 full, the fuel level sensor calibration can be lost. It can be recalibrated with Porsche diagnostic equipment. I think the tank needs to be full to do this.

I learned this when my engine stopped on track at Streets of Willow.
When the engine stopped I looked at the dash & saw the oil warning light on & fuel level @ 1/4. I thought engine lost oil pressure & engine quit as a result. I coasted off track into the infield. after the run session ended I got towed to the parking lot (level ground) Oil level was fine on dipstick & fuel level was fine according to gauge. After a hour agonizing over what damage I had caused to my engine, I realized I wanted to build it anyway so I turned the key & it started & ran fine for about 5 minutes as I drove up & down the parking lot. It ran out of gas again & died.

Don't let the dealership sell you a fuel level sensor without trying to recalibrate what you have. If you do need a new level sensor, consider replaceing the fuelpump also as many are dieing from old age these days.

You can try a recalibration. You will need a PST2 or PIWIS. There must be 16 liters of fuel in the tank (so you have to fully drain it, and add back 16 liters).

Did the gauge ever work below half?

I fill it up and it goes to full. Drive at least 300 miles and put another 12 gallons in and it goes back up. Never did go below right at half tank. So I know it was lower than half tank

I'm telling ya, the fuel gauge float is snagged on something. Easy fix. Nothing to do with scan tools or draining the fuel or anything. Perhaps one of the zipties or clamps that hold the wires back slipped or fell off so now a wire is hanging out there that is snagging the float.

+1

This happened to me, the float would catch on a wire and not show a full tank.

I have a similar problem - gauge only goes up to 3/4 and stays there. Works fine once fuel level goes below that. Been living with it but now I'll give it a look.

What do you do to fix the float?

If the gauge USED to work, then it could be a faulty sending unit but if it has always acted this way than it's probably hanging up on the fuel lines inside the tank. I just replaced my fuel pump and ( with pelican's DIY tech article) noticed this potential problem and had to use 2 additional zip ties to tie the lines to the fuel pump/sending unit post on the opposite side than the float. It's easy to see that if someone was in a hurry, they would just lower the assembly in and assume all is well.
To repair this problem after the fact one would have to pull the assembly out of the tank. Study what's happening and use zip ties to force the lines to bend along the inside of the post. Pelican parts has a very helpful DIY article. It's best to do the job when there's very little fuel left in the tank. Also, beginning in MY 2002 a different set-up was used and I'm not sure if the above applies or not.