Weird Fuel Problem

[dyerhaus]

I’m having a weird ‘fuel thing’ with my 2001 Porsche 911… So, I’ve been thinking it gets terrible gas mileage, compared to my 986 Boxster. I expected slightly less, but, it seems pretty bad. Now, I can’t help but wonder if there’s actually something amiss about it.

 

When I fill the tank completely—and I mean ‘topping it off’ to get every last drop in, my fuel gauge usually looks like this (see the first picture, 01).

 

That picture was taken immediately after starting the car after filling up the tank (I was still at the pump). There have been occasions where the needle has gone all the way to just slightly past the 4/4 mark (just like the Boxster always does), but it usually lands below as seen in the photo.

 

However, today I was down to the warning light coming on telling me I’m low on gas. I stopped to fill it up and it only took about $30 worth. That’s odd, with gas prices here and filling up an almost empty tank, that should have been between $44 and $48 (that's what the Boxster runs). I tried to top it off but it wouldn’t take any more, as if the tank was full.

 

So, I got in the car and started it, and (just like before) this picture was taken immediately after starting the car after filling up the tank (I was still at the pump) - (see the second picture, 02).

 

Just barely over half a thank.

 

Any idea what could be going on with this?

[RFM]

Given the fuel system management using calculated values, it is recommended to refuel the car with the ignition off in first place.

[dyerhaus]

9 hours ago, RFM said:

Given the fuel system management using calculated values, it is recommended to refuel the car with the ignition off in first place.

The ignition is off when I refuel the car.

[Loren]

C2 or C4?

[dyerhaus]

55 minutes ago, Loren said:

C2 or C4?

C2. Specifically, early 2001 model if that makes any difference. 

[Loren]

The fuel tanks and plumbing are very different between the C2 and C4 due to the front drive axle in the C4.

C4's historically have more fuel tank issues (mainly with calibration) because their are two sides to the fuel tank - a saddle bag layout.

 

If your tank is not filling all the way then I would suspect a crimped fuel fill hose or one of the other lines for vent return.

 

[Schnell Gelb]

This may help:

 

[judgejon]

does gas actually flow easily into your gas tank?

there is a known issue with the vent valve not opening and preventing tanks from easily filling.

If you are getting a good flow of gas from the pump, check your fuel sender, and then check the fuel gauge.

I think, I hope this is wrong, but I remember reading that if a gauge is faulty the entire instrument cluster needs to be replaced.  Loren?  RFP?

there are several articles on the filler valve issue, the search engine will be your friend.

good luck

[el zacko]

Had similar problem at the gas station took 20 min for 1gal. Went home after looking through forms pulled the battery and tray and stinking rats! Put the wires back together. And bam works perfectly.