Fuel Level Sender Calibration Issue

[logray]

99' 996 C2 history.

Gas tank gauge never goes to Full. Can only fill to about 3/4 full. It can go to about 4/5th's full even if I sit there all day long topping it off, which is a bad idea. Tried rotating filler nozzle 90 degrees, 180 degrees, slow speed, medium speed, doing a hand stand and singing voodoo chants. None of that ever worked (except perhaps the chanting). Checked for fuse E6 is it? It is fine. Besides gas never poured back out of the nozzle... so...

Finally decided to tackle the issue the right way.

Drained fuel tank. Added 12 liters of fuel. Performed tank calibration with PST2, it read 2.43 US gallons calibration successful.

I though, hmm.... that's strange 12 liters of fuel is 3.17 US Gallons. Perhaps the PST2 is smarter than I or that saying 2.43 US Gallons is it's funny way of saying how far out of whack the sensor is. Or perhaps this is a conversion issue and it really means "UK Gallons" which is actually 2.63962989 Imperial Gallons. Which would make more sense if it told me 2.43 Gallons.

So off to the filling station and guess what. Same issue. Couldn't fill up the tank. So I surmised that either I didn't drain all the fuel or perhaps some other issue.

I stumbled upon TSB 2015.

Back into the gas tank I went, this time it was easier having done it just before. Drained all the fuel this time, down to the last drop. Until the tank was dry and I could see no more fuel and it began to evaporate off the bottom.

Tie wrapped the fuel lines per TSB 2015 and ensured nothing was preventing the fuel sending arm and float from going to maximum position.

Reassembled. Added precisely 12 liters of fuel (even more careful as to the amount this time).

Hooked up the PST2 and tried to calibrate the cluster again.

It read, "tank calibration exceeds tolerance limit" no matter how many times I tried and displayed anywhere between 2.17 and 2.23 US Gallons on the PST2.

Anyhow, the gauge still works and displays some fuel, however at this point I have no idea if it is accurate or not. I put in about 8 gallons and it reads just below 1/2 full now, which I suppose makes sense?

However the gas tank refill amount is appx. 64 litres (14.07 imp gallons or 16.9 US Gallons) [including or excluding? a 10 liter reserve = 2.64 US Gallons]. BTW the WSM has wrong conversion amounts for liters to imperial gallons.

Do you think it could be the fuel sender at this point ($165) or am I missing something here?

Thanks.