street rod

My 2001 C4 has the issue of sometimes only filling up to show 3/4 tank and also only goes 150 miles (about 8 gal) on a tank which I believe means its only using 1/2 or one side of the tank. I found info in an old post which I copied below with a comment about a TSB. My question is can I drive the car like this until the next time I have it in for service then get it fixed, or is there some reason to get it fixed immediately? I could live with it for 6 months or whatever if its not going to cause other issues.


"TSB's can be found on Renntech, but you must be a member to access them, and they are "view only".

There is a TSB #2015 dated 5/99 that addresses "Difficulty filling fuel tank" and "Running out of fuel due to incorrect fuel gauge reading".

Solution: "the routing of the flexible fuel hoses in the fuel tank must be modified. Additionally, on the 911 Carrera 4, it must be ensured that the jet pump end caps are in place and the connections for the two jet pump lines are properly connected." The TSB then provides instructions for this work.

knfeparty

This is going to sound crazy, but my permanent solution to this problem was filling up the car with the gas pump handle upside down. It never trips off early now. Have you tried that?

street rod

Thanks I will try that. Today after filling the tank and the guage going to 3/4, I turned the car on then off, and then it allowed me to fill it to full. Did you also have the other issue with only 1/2 of the tank working?

Pac996

Problem is you can only put 8 gallons on one side and the other has to be liters. Makes sense right?

Darn I'll give it away. The tank is fine. It's the gauge that is wrong. You fill it up it is a full 16 gallons as far as I know. Only problem is gauge is off normally showing less fuel. Some probably figure well they'll get the 300+ mileage and keep going while the tank says refill with the warning light on figuring the 300+ is the key factor. Don't forget if you are heavy on the pedal and zooming around it;s 200+ till ping ping sputter sputter where is the gas station in coasting range. At least I'm thinking you aren't using a two chambered tank with a valve. Are you?

Loren

Only C4 (and C4S) have a problem with this - it is even noted in the Owners manual.
The C4 has a "saddle bag" fuel tank - that is, part of the tank sits on each side of the front wheel drive axle. So the fuel level sender is only on one side and it does not know how much gas is on the other side - it guesses. So if you let the tank get too low it can get confused.
The easy fix is to always fill the tank as it reaches the 1/4 mark.

Pac996

Didn't know that about the C4's and it makes sense now. If the departure from both sides being level and storing seperate amounts is above 1/2 it's a tough game. Normal refill level for safety is before 1/4 to keep from stirring the tank bottom so it won't pump gunk in the filters or pumping air that causes excess heat in the pump since the high speed fuel injection pumps needs fuel to cool them.

Sorry about not knowing the saddle tank configuration and joking around Seems the C4 gives better excuses to sling the car around in turns to make sure the drawn from side has fuel. I guess the question would be what side is the fuel pick up in and fuel level of seperation so that an opposite side hard turn should load up that side with fuel when levels are low.

cardsrule

I bet your battery died recently or you disconnected it with 1/4 or less fuel in it. You are going to need a tester to recalibrate it and a work shop manual.

Its kinda a pain in the butt...

Dennis C

I have issues with certain gas pumps. This is even true of different pumps at the same gas station. I've found one that allows me to fill completely up every time, so that's the one I use now!

I've also heard of a blown fuse (number E6, I believe) that's part of the vapor recovery system. If this fuse is blown, it could cause your problem. If this fuse is blown, it could be caused by a chafed wire.

I recall reading on rennlist somewhere that underneath the carpeted cover on the passenger's side of the center console, you'll find a 4 pin connector with red wires with green stripe. These wires can chafe near the airbag mount, causing a short and a blown fuse.

street rod

I bought this car 2 months ago and it has been doing this since the first time I filled the tank. I did put in a new battery but was doing it before that also. The fill to 3/4 thing is manageable using the tricks knfe and Dennis mentioned but the fuel gauge goes down very quickly and shows empty after about 8 gallons is used even though its a 16 gal tank. I talked to Hans at RUF today and he said it could need reprogramming or possibly a float issue. The next time I take it in for service I will let him fix it. I will try filling the tank before 1/4 and see what happens. I wonder if I would keep driving it for another 100 miles or so after it shows empty, then filled it if that would make the gauge read closer to normal again?

OGWGFIW

@ Dennis,

Same issue for me. Some pumps will give me a full tank while others shut off a little below full and I have to trickle in the last bit.