Fuel gauge calibration question

[Guest]

When my fuel tank is full, the gauge only reads a little over 3/4 full. When it reads empty, I can fit about 60 litres in the tank before it is full. Also, when it reads empty, the reserve light hasn't come on (I haven't been brave enough to try driving until it either comes on or the car stops).

Does anybody have any ideas what might be going on? Is there an adjustment in the fuel gauge system anywhere that would let me correct the offset? Or could it just be that the sender or wiring has gone high resistance?

Any input would be very helpful. It drives me mental [&:]

James

 

[sawood12]

Sounds completely normal to me. My guage reads a needle's width down from full when full and I usually fill up with around 60 to 65 litres after about 300 to 350 miles as the needle approaches the red. The tank is about 80 litres capacity so there is plenty left in there but like you i've never taken it much further down. From previous threads there are suggestions that this is due to either corrosion on the terminals at the back of the guage or just poor electrical earthing which the 944 does suffer. Some people reckon that if they fill their cars up and not drive them for a week or so the guage will then read full which suggests to me something to do with the sender. Either way it's common and I think the guages on 944's are not too hot after all these years. My volt meter reads around 13v (less than 12v by the time my A/C, lights and wipers are on) but I'm actually getting about 14.5v across the battery terminals, and my temp guage never gets into the normal range unless i'm stuck in traffic.

There are similar symptoms of poor eathing as well such as slow operation of the electric windows.

 

[944Turbo]

I have also heard the float can sink due to fuel leaking into it. However my guage will read full but I have to put the last few pound in V. slowly after the pump has cut out once. I think the tank shape means it takes a while to let the rest go in. The light comes on when the needle gets to the empty line lighting up a further section below. I think I have got half way down this section before filling up but it was a long while back so it could be my memory playing tricks on me. Not sure how far down you have to go to run out though!
Tony

 

[Fen]

I have never run out and I generally accept that after the light comes on I have 50 miles tops left in the tank. I think once I went about 53 miles with the light on looking for a Shell station (then just any station!) a few years ago. Mine reads full when it's full as did my cab so I can't really offer any advice.

 

[mik_ok]

didn't realise there was a low-level light [&:]

 

[John Sims]

Mine reads just over 3/4 when normally full but if I rock the car (not easy), and dribble the last of the fuel in, I can get it up to pretty well full full on the gauge. I think the tank airlocks which stops the full fill. If you pull the nozzle half out when it clicks off and then fill slowly it is surprising how many bubbles of foaming fuel come back into the filler tube.

 

[Fen]

I always do the half out and trickle in thing. I hate filling up so I'd always rather spend £70 than £60 if it means I get to go for longer without filling again. Main reason the Pug is going to make way for a diseasel is so I don't have to stop so often.

 

[sawood12]

My gauge is also extremely sensitive to ground angle. If i'm half full the gauge can easily be deflected to quater full or three-quarters full on a fairly mildly sloping hill depending on which way i'm pointing.

 

[Fen]

I used to love my 3.2 Carrera gauge - 1/4 tank variation between acceleration and braking []

 

[Guest]

I have the missing top 1/4 as well, just figured it was an idiosyncrasy of the car. I'll try the dribbling it in trick, although once I get past the £60 mark I start my random mutterings of how much I hate fuel tax, the Government, unfair victimisation of the innocent motorist etc... so try to avoid.

 

[cornishgrose]

I always drive around in the 1/4 tank level and find that the fuel tank is blooming good in the fuel reserves. I can remember only a month ago that the fuel light came on and I knew the next one wasn't for another 40 miles. I went approx 30 miles and found a small garage that was open. Although I always put £20 worth in when I fill up and that reads about 1/3 to a 1/2 a tank. Either I have a magic fuel tank or fuel prices are alot more up country.

 

[Fen]

ORIGINAL: cornishgrose

I always drive around in the 1/4 tank level and find that the fuel tank is blooming good in the fuel reserves. I can remember only a month ago that the fuel light came on and I knew the next one wasn't for another 40 miles. I went approx 30 miles and found a small garage that was open. Although I always put £20 worth in when I fill up and that reads about 1/3 to a 1/2 a tank. Either I have a magic fuel tank or fuel prices are alot more up country.

The gauge isn't linear. Half a tank on the gauge is a lot less than half a tank. If you brim it the needle won't even move for 70 or 80 miles which is enough to take you from 1/4 full to the light on.

 

[Guest]

ORIGINAL: mik_ok

didn't realise there was a low-level light [&:]

 

[Fen]

ORIGINAL: flamingeye

ORIGINAL: mik_ok

didn't realise there was a low-level light [&:]

Note though mik that it doesn't come on with the other lights at ignition for a bulb test so you get the joy of wondering if it will light up of the car will run out for the first time. All 5 of mine have worked.

 

[Guest]

Another favourite from my collection.
Doesn't everyone take pics of their fuel guage ?

 

[John Sims]

ORIGINAL: flamingeye

Another favourite from my collection.
Doesn't everyone take pics of their fuel guage ?

You need to get out more. [] I tend to find the rev counter and boost gauge more entertaining.