Strange fuel/gauge problem - any ideas?

Had a strange problem with my fuel gauge on Wednesday & wondering if anyone has had similar? Had the car 9 months & not a blip/problem...was off for a 2 day trip on Weds so filled up Tues night - all OK. Drove about 350 miles and the range ws down to 15 miles when I was in the middle of nowhere a.k.a. mid-Wales Anyway, had to stop at small Murco garage in a small vilage & put £15 of unleaded in (no super on offer)...and drove off. Only to realize 2 miles down the road that fuel gauge was still registerng (virtually) zero. Did a u-turn & went back & finally cinvinced myself that the problem was not with their pump but with my car's gauge so drove to destination. I knew 3 gallons was enough to get me there so assumed a trip to OPC ASAP was in order when i got home. Next morning, I put in £35 of super unleaded for my onward journey and, hey presto, the fuel gauge etc all sprang into life again! A temporary glitch? An problem with ordinary unleaded - although I have used it in the past without problem. Particular brand? Anybody else had similar? Any theories? :?

Vague idea this has been covered before. Iirc it has something to do with the sensitivity of the sender; if you only have a small amount of fuel in the tank, it is not enough to cause the guage to register. Someone who knows a bit more may be along in a minute though to help.

If you let your fuel level get down to where you get the fuel warning you need to fill it up to the maximum, or near to maximum to 'reset' the fuel gauge, otherwise as with yours it will not register the fuel you have put in. Its the same for 997s too. No idea what the reason is behind it or if it is intentional.

Cheers guys, well getting it over half full seems to have done the trick....but is still seems VERY odd/weird :shock:

What is weird is that you can get 350 miles out of a tank. :shock: As Barney said, if the fuel level drops very low you need at least half a tank to reset the thing. Nothing to worry about and nor is putting in a little 95RON every now and again if super is not available.

Yep, sorry...a chunk of it was motorway cruising in 6th

I was speaking with my neighbour who also has a 911, and he was told by the local OPC that on a 996 you shouldn't run the tank much below 1/4 full as due to a design flaw the float can jam. If severe it requires the tank to be drained and the float to be freed off, which is obviously an absolute pain. I experienced a 'dead zone' when I ran the tank down (before the above conversation), I put £10 worth of fuel in as the nearest petrol station did not have Super, and this did not register on the guage. Fortunately when I filled up complety the guage was fine. Since that time I fill up when I get to around 1/4 tank

Sounds like I'm not alone Although I've regularly ran it to almost empty before refilling so I'm not entirely sure that's the full story :? First time I've put so little in though I guess :roll: :idea:

I agree - both theories sound a bit odd. The first one requiring the tank to be refilled to reset the guage, could only serve to un-nerve the owner. The second one being a design flaw seems a little careless (I'm a design engineer and I think I'd be lucky to retain my job if I let that through!) Don't know whether C2s or C4 have different tanks - I have a 3.4 C4 and my neighbour has a 3.6 C2. All very odd - yet another 'unique' aspect of 911 ownership - just like the oil level sensing! Brilliant car - but the fluid level sensing seems to be a bit haphazard!

First one is not a theory. I read it in the service manual. 3 gal = £15? That is $10 a gallon in the US!

yep - it's approx £4.50 a gallon in the uk of course that's the equivalent of only £3.75 per US gallon!

Well, in a further attempt to "solve" the mystery, I just rang my OPC (Swindon) and asked their opinion. Nice lady there initially asked if it was a C4...it's a C4S and she said it's a known (problem/design feature/)issue that you have to put about 25/30 litres in them before it (re-)registers on the fuel gauge. She couldn't explain why and say if it was documented anywhere. Anyway, there it is...don't know if that helps or adds to the confusion!

Interesting that the guage goes progressively down to zero (on my C4), and then needs approx 5 galls to get it to register again. Either they have a diabolical sensor with massive hysteresis, or it sticks in the down position. I can't help thinking that the float must end up at some near vertical angle when empty and therefore needs plenty of fuel to get it floating again............ I think I'll continue to fill on 1/4 to be safe!

On my C4S I need half a tank for the needle to register it. I did find whilst doing a few laps at Silverstone that high-G cornering helps 'loosen' the needle

The float should NOT jam if you let the car run low on fuel, however the float does not actualy touch the fuel much below 1/4 tank. If you let it run low and only add ten pounds or so the fuel still wont reach the float and hey presto the car does not know the fuel has been added. The car systems calculate the fuel use electronicaly at less than 1/4 tank thus the gauge still appears to work going down.