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:



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):



Just barely over half a thank.

Any idea what could be going on with this?

Hurdigurdiman

The second photo shows the car slightly over heating. Not that that is anything to do with the fill mark. The 'mileage left' 188 seems to match up with between half and 3/4 full mark. So what are you wondering about? The fact that the pump 'cut off' and would not take any more gas? If so, maybe the breather valve did not open on that one occasion. I would run the car and try to fill it again.

speed rII

Is your car C4 and replaced battery recently? On C4 the fuel gauge sender calibrates it self after battery replacement. So fuel tank must be full when doing this.

Or the sender is broken. Or tank breather valve is not working and you cant fill the tank properly.

Mike Murphy

Common problem. A search will show a lot of folks can only put in 12 or 13 gallons into a tank that actually fits 17 gallons. The gas tank gauge needs to be recalibrated.

dporto

My Porsche dealer tells me "the gauge can't be recalibrated, you have to replace the sender"... I didn't bother getting a price, as nothing they do costs less than a grand... I reset my trip odometer and refill the tank when I reach 200 miles

dyerhaus

My car tends to always run at the temperature. What I'm wondering about is why I can never fill the tank. The fuel pump cut off as if the tank was full, I tried topping it off, but the car simply wouldn't accept more gas. But when I turn the car on, the tank is just barely half full. The tank is never completely full. So while "Mileage Left" may be accurate at 188, the tank should have been full, but it wouldn't let me fill it past the half mark. My 986 Boxster doesn't behave this way, both cars have the same system.

JayG

Come on Hurdi, that is not overheating at all

I find that on some pumps in order to get a full tank, I have to turn the nozzle 180 deg so the bottom of the handle is up

dkraige

Measuring the volume of fuel dispensed in gallons rather than dollars would probably help people discern and comment better on what might be going on.

Now if you'll excuse me I have to go buy a little less than 4 dollars of milk

human911

I had this same issue and it happened to be the tank breather valve.


Fixed my issue.

mrjonger

I do this too and I can fill all the way. Did a quick google search and it looks like I should take a look at that vent. Bad vent resulted in a bad sender and misshaped fuel tank.

http://forums.pelicanparts.com/boxst...t-filling.html

Schnell Gelb

Note that the 'vent to atmosphere' expedient mentioned in the link would cause and Evap System CEL -so is a get-you-filled-&-home idea only.

Mark I

Gotta be with Hurdi on this. I'd be concerned about that.

Kalashnikov

Your temp gauge is fine. In Phoenix Summer, in stop-go my 2002 tip sometimes would go past 0.

And on top of that, unless you hook up the ACTUAL OBD II reader and read your coolant temperature, the reading of the gauge is basically the "idiot" light warning. If car gets too hot, needle will go in the red. As long as needle sits in the "habitable" zone of 180 digits, you are fine.

And happy 4/20.

mrjonger

Yup, saw that. Good looking out though. I've been meaning to check the brakes anyway.