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C4S fuel gauge

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Ha anyone else seen the problem where the fuel gauge does not register if you do not fill it above about halfway (10 gals or so)? Basically, if I leave the electrical system on while filling the tank, the needle does not move from empty until I get to around 10 gallons and then it pops up to half a tank or so. I asked the dealer and they said that this was a common problem because of the "saddlebag shaped gas tank". I find this hard to believe, but can't find any schematics of the fuel tank. It seems to me that if this was the case, as you went around a corner the gas would slosh over the middle and cause a significant change in dynamics of the car.

Any thought?

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Your dealer is right. Perhaps this from TSB 9/99 2015 Carrera 4 – Running Out of Fuel (dated 10-14-99) will help.

In all current models except the 911 Carrera 4 (996), the fuel level warning light (reserve) illuminates when there is approx. 10 liters of fuel remaining in the fuel tank. When the reserve light comes on, the driving-distance-on-remaining-fuel (trip computer) is calculated by monitoring the fuel consumption signal (ti), and continues until the fuel tank is empty (or refilled).

In the case of the 911 Carrera 4 (996), the shape and configuration of the fuel tank prevent the fuel level sensing system from being able to physically read down to a level of 10 liters. Therefore, on the 911 Carrera 4 the driving-distance-on-remaining-fuel calculation begins when the fuel reaches a level of 19 liters (approx. 1/4 tank).

As fuel is further consumed below 19 liters, the amount of fuel remaining in the tank is a calculated value. The calculated value is derived from the fuel consumption signal (ti), and continues until the fuel tank is empty (unless the fuel tank is refilled).

Whenever the fuel level is less than 19 liters and the ignition is switched off, the fuel-level and driving-distance- on-remaining-fuel values are stored in instrument cluster memory.

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Thanks for the quick reply. that is interesting, although I would be curious to see what the shape of the gas tank was. If it is "saddlebag shaped", again it seems like it might change the dyanmics of the car as the critical mass of gasoline goes sloshing over the "hump" in the middle.

Does anyone know of any schematics/ photos of the gas tank?

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