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Fuel gauge!!!!!

OnOneSteve

Member
Joined
10 Dec 2013
Messages
13
I don't seem to be having much fun since becoming a 911 owner :x

I've just been and put some fuel in my 996 C4 and the fuel gauge hasn't moved!!
Can they take some time to catch up or do I have a problem?

I had a Boxster previous to this and didn't have an ounce of trouble in 18 months
 
Hi,
You don't have a problem, you have a Carrera 4!
The front diff' required a redesign of the fuel tank, also front mounted, to keep it simple, think of your tank as two saddles, if you only put in a small amount of fuel from empty, it will never move the gauge.

ScottUK
 
Phew thanks for that. I did only put £20 in and it was almost empy!!!
Guess I'll not have to be such a tight arse next time.
 
Haha, i used to find this with my 4S.

Trouble is you never know how much fuel you have in unless you always fill it up...

Having said that I did find that if I drove for more than 30 mins or so the fuel guage sometimes figured it out! :?:

One of the little things that give the Porkers so much character I spose!
 
It won't register (on AWD chassis cars) until you fill it with at least 19L

You have an AWD chassis, so you have a split fuel tank (ie "separate" sections, rather than leaking!)

The AWD models (so C4, Turbo etc) have additional driveshafts to and at the front (obviously), but this poses problems for the original position/size of the fuel tank.

So AWD models have a reshaped tank, to straddle the driveline and new chassis strengthening structures and driveshaft mountings etc.

The fuel gauge technically only operates above the "flat" of the tank, any fuel level below this is "guessed" by a fuel tank algorithm and sent to the electronic analogue display on the dash.

This means if you are empty and add only enough to fill the lower section of the tank, the sensor is still dry and the gauge won't move (ie under-reads fuel volume)

This might sound stupid, but it is preferable to having the sensor in the base of the tank and over-reading and hence you thinking you have more fuel.

Once enough fuel is added to fill the lower section (ie up to the "flat") the sensor is "wet" and the gauge reads as normal (ie a measure of the entire tank).

This "flat" volume is usually about 1/4 tank (below 19 litres the system actually guesses your remaining fuel from fuelling data, only once it is refilled above this level again is the alogorithm reset and continuous reading handed back to the sensor).

Note: in the diagrams below the "2WD" and "AWD" refer to chassis type, this means as GT3/G2T models use AWD chassis and hence use AWD tanks.

996_fuel_tanks_209.jpg
 
As a footnote to this, when I had a 996 GT3 (which while a 2WD car actually uses a 996 C4 shell for rigidity, hence has the same tank) I had a couple of instances where it failed to register fuel. Both when running it low on track and it then brimming it but no indication that any fuel had been added. In both cases a couple of laps of the Nordschleife later it was fine.
 
Yeah thanks for that guys.
Guess I'll put at least £40 at every visit now. It all make perfect sense for the tank being modified to accommodate the front diff. :worship:
 
Disco said:
As a footnote to this, when I had a 996 GT3 (which while a 2WD car actually uses a 996 C4 shell for rigidity, hence has the same tank) I had a couple of instances where it failed to register fuel. Both when running it low on track and it then brimming it but no indication that any fuel had been added. In both cases a couple of laps of the Nordschleife later it was fine.

GT models mentioned above (although apologies for "G2T" typo)

The problem with dropping the fuel level to really empty and refilling is independent of the algorithm issue.

If the fuel drops below the bottom of the gauge capillary, you get airlocks (and measurement).

Fortunately, overnight park-up or continued use will clear it.
 
Gt4 please tell me you cut and paste that explanation not retype it every time it gets asked :eek:

One for the FAQS maybe?
 
Of course I cut a paste it.

I have no shame in that, given I wrote it.

I don't draw the explanatory diagram in MS Paint again either!


I do sometimes modify it depending on the vanilla of the question.

(I really do need to correct the "G2T", but I only just noticed it this time - :oops:).


Sometimes putting things in FAQs is the best way for them not to be read!

There is always the search button, and posting so many times at least gives someone a fighting chance of finding it.

Cutting and pasting means it is no more effort than posting any FAQs link anyway.
 
LOL :D A belated "welcome" :thumb:

Another C4 owner thinking, "is there a feckin hole in my fuel tank?" :D

I sh@t myself first time it happened :D

Not something they put in the manual :D

Dan :)
 
ScoobyDoo555 said:
Not something they put in the manual :D

:dont know:
 

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I stand corrected - must have missed that bit. But good to point out.

That said, being in the UAE, surely fuel is not exactly an issue - just fill it up at a stupidly cheap price! :D <jealous>
 

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