Strange strange???
I normally fill up the tank when the light comes on. It takes max 32 liters and the manual says it should take about 60 liters. After having filled (with the 32 liters) the meter shows full tank. When driving nicely, the car goes about 10 km/l thats ok. Range on a full tank (untill the light comes on is about 290 km
Its a C4

The tank seems too small.?

Any suggestions?

Kind regards Michael

 

Something is not correct, that's 8 gallons on the conversion. Was the tank changed for some reason by the previous owner? You should have a 17.7 gallon tank. Also, I wouldn't run it until the light is on, I usually fill up at 1/4 a tank left. I would have someone check it out. Is the tank separated into two with baffles?

 

I have a 1999 C4 6 speed manual trans. It's fuel tank is 16.9 gal. (at least that's what the spec's say). I too have a problem (I think) with my fuel gauge reading improperly (it seems to stop moving between 3/4 and 1/2 tank). My "fix" is that I reset the trip odometer with every fill up (gauge reads full) and when I hit 200 mi. I fill up again. When I refuel with this scenario I generally have used 10 - 11 gal. yet the gauge is still reading over half... Does this sound anything like yours?

 

http://www.renntech.org/forums/topic...-tank-content/

Another friend wrote this, and the problem matches yours. Seems like in the C4 there is still 19 l of gas left when the light comes on. In my car (a 2001) the computer says still 200 km when the light comes on so it is probably right. One day I will take it for a ride with a jerry can an run the car dry, and see if the theory is correct.

Kind regards. Michael

 

The fuel level system is out of calibration or the system is faulty.

The C4 tank is over 16 gallons, I'm not sure if it holds 16.6 or 16.9 gallons.

Because of the AWD feature the tank is of a saddle design, with each saddle having a siphon jet to pull the fuel out of the bottom of the saddle so the entire tank's contents is available. (Cars that have a siphon jet fail run out of gas at about a half tank when the tank level system is working properly.)

Oh, the fuel level system is hardware to about half a tank then the on-board computer takes over and calculates the remaining fuel level via software based on some input from various engine sensors or the DME (like fuel injection pulse widths, etc.).

To recalibrate the fuel level system(s) requires special equipment -- access to a Porsche diagnostics computer (a Durametric may abel to do this) -- and the tank's level be drained and then a specific amount of fuel added and the level measuring/software calculation system reset.

You might be able to "fix" this by filling up the tank until the gas nozzle shuts off.

Then with as little driving as possible get home and disconnect the battery for a while. Based on what it takes to recalibrate the fuel level system(s) -- which I covered above -- I doubt this will work but you might try it. If you do try it be sure you follow the proper steps when disconnecting and connecting the battery. Bad things can happen to nice cars if this is not done correctly.

 

Per the 1999 Owners Manual... "Refill volume approx. 16.9 U.S. gallons/64 liters, including approx. 2.6 U.S. gallons/10 liters reserve."

Reading through threads on a few different forums, it seems like a Fuel Calibration at the dealer is what's needed. It's also possible that disconnection the battery with a full tank of fuel may reset it - I should probably just attempt this...If I do, I'll post back and let you know what happens.

 

Some models have a 16.9 gallon tank, my Boxster for instance, but I thought the AWD cars had a slightly smaller tank, something like 16.6 gallons. But maybe not.

Well, I just checked my Turbo factory manual and it lists the fuel tank capacity at 64l for ROW cars and at 63l for USA cars. Both tanks have a reserve of 12 liters.

64l is 16.9 gallons and 63l is 16.6 gallons so maybe that's where I got the info there was a different size of fuel tank between the AWD and regular model vehicles.

The fuel recalibration thing is what I think you will have to do, end up having to have done.

But try the battery disconnect if you want. While I have to be honest and say I do not think it will work, I hope I am proven wrong.

If you do the battery disconnect thing, I must stress you have to be very careful for if you do this wrong you can possibly do some electrical damage to the car's DME.

 

For what it's worth, mine has never shown a full tank and I always fill until the pump knocks itself off at the pumps. I refill when it is showing around the quarter full mark and never check as to how many miles to the gallon I am getting.

 

Ha! That seems to be the opposite of what mine does - it seems that problems with the fuel measuring system are fairly common with these cars - pretty hard to believe in this day and age...