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Thread: Why is my fuel tank getting smaller?

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    Why is my fuel tank getting smaller?

    Hi everyone,

    I hope that someone who has some good car knowledge can help me find an answer to this puzzle please.

    I will explain in detail below but I just can't physically put as much fuel in to the fuel tank as I have been able to in the past. This isn't a MPG question; but a full tank capacity question.

    The car in Question is an N16 Nissan Almera 1.5 Petrol 53 plate which I have owned since January 2005 and has been very reliable indeed (the most reliable car I have ever owned).

    The car has a 60 litre fuel tank according to the manual and I can confirm it must be around this size because in the past when I have refuelled, I normally put in around 55/56 litres or so to brim it when I am just above the red mark.

    Historically, on a full tank I have been able to complete 11 round trips to my workplace and home (approx 50 miles round trip); this would leave me just above the red mark and this is when I would refuel with about 55/56 or so litres. Also, when full I would get 2 rounds trips to work before the needle moved down from "above" the Full mark to the Full mark - hope that makes sense.

    Now, over the last few months I began to notice that I was only getting 10 round trips to work and only 1 round trip before the needle moved down to the Full mark instead of the usual 2, which I put down to the cold weather etc etc.

    But over the last 3 or 4 refuels I have noticed that I am getting less fuel in to the tank from the pump. In fact, on Saturday I had run the car so low that the fuel light was on, I was almost at the bottom of the red mark and the fuel computer couldn't even work out how many miles I had remaining; in fact, this was the lowest I had ever run the fuel level down to. So I went and refuelled and completely filled it up to the click, and then a couple of little bits more and all that had gone in to the tank was 51.5 litres. Where has my other 8.5 litres gone? I would understand the odd litre or two, but we are talking nearly 2 gallons here!

    I looked back over the last couple of receipts and they were all in the 52-53 litres range as well. The MPG seems to be about right too.

    It just seems like something has made the fuel tank significantly smaller almost like putting a big dent in it would do or something along those lines. I have had a look under the car - not that I really know what I am looking for - and if what I think is the fuel tank is the fuel tank, then the bottom of it looks fine at least.

    Does anyone have any idea whatsoever that could be causing this?

    Any ideas, advice or tests would be greatly appreciated so that I can take it to the garage which some idea of what to tell them.

    Thanks for taking the time to read this.

    All the best,

    Moley

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    Senior Member Tonka777's Avatar
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    Re: Why is my fuel tank getting smaller?

    Probably a sensor issue with wear and/or age.

    Clearly the fuel tank cant change size, and as far as i know, they only vent through the filler cap, so it's unlikely to be trapped air.

    The only thing i can think of is that there is more fuel left in the tank when it indicates just above the red mark than there was when you first bought the car.

    I guess you could try dipping the tank, or weighing the whole car, but with no data from 3 or 4 months ago it'd only be guess work.

    Have you always used the same fuel station? When were their pumps last calibrated?

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    Drum & Bass Till I Die deejayburnout's Avatar
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    Re: Why is my fuel tank getting smaller?

    Sounds like a sensor fault to me.
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    Re: Why is my fuel tank getting smaller?

    Plastic tanks can implode, get it checked out by a garage.

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    Re: Why is my fuel tank getting smaller?

    Perhaps you are now filling up at a pump which is on a slight slope, so the tank is at an angle and gets a bit of air trapped in it.

    Either that or you have a bad connection to your fuel sender. They are a simple device that works by resistance, so if some resistance is added then it will look like the tank is emptier than it really is.

    On the positive side, you have a bigger reserve when the tank reads as empty so you are less likely to run out

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    Pork & Beans Powerup Phage's Avatar
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    Re: Why is my fuel tank getting smaller?

    Insert "We're in your car, drinking your fuel" meme here
    Society's to blame,
    Or possibly Atari.

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    HEXUS.timelord. Zak33's Avatar
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    Re: Why is my fuel tank getting smaller?

    first: get under the car and check for dents in the tank

    If it has a big one, you know the problem. I once drove over a large piece of rubble and it mangled my tank

    second: if the tanks ok in size, it's worth considering the following: get a NEW fuel filter fitted, so you have no chance of contamination, and then buy a petrol can and fill it with spare fuel

    then drive your car as long as you dare, until you truly find out how low it will go! I think, as the guys say, the gauge is miss reading from old age.

    IF you brave it and drive as far as you used too.. and then refuel... you know it's just the cars guages and sensors getting old

    you COULD get a new tank sender unit... but why? She;s an old girl now... learn her vices and live with them


    I've sold a few Almera's and they truly are bullet proof.

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    Pork & Beans Powerup Phage's Avatar
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    Re: Why is my fuel tank getting smaller?

    This is the bikers fuel gauge. How far did you you used to go before filling up ? 300 miles ?
    Reset the trip miles when you fill up. Then buy more fuel at the 290m mark
    Society's to blame,
    Or possibly Atari.

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    DILLIGAF GoNz0's Avatar
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    Re: Why is my fuel tank getting smaller?

    Someones slipped a few kilos of cocaine in the tank maybe?

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  10. #10
    DDY
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    Re: Why is my fuel tank getting smaller?

    An 8.5L dent?

    That would be a big dent.

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    Re: Why is my fuel tank getting smaller?

    Quote Originally Posted by DDY View Post
    An 8.5L dent?

    That would be a big dent.
    depends if it was longtitudenal and creased the tank, creating a barrier to it sloshing about.

    Quote Originally Posted by Advice Trinity by Knoxville
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  12. #12
    DDY
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    Re: Why is my fuel tank getting smaller?

    A longitudinal dent?

    That would be a long dent.

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    Re: Why is my fuel tank getting smaller?

    Quote Originally Posted by Tonka777 View Post
    Probably a sensor issue with wear and/or age.

    Clearly the fuel tank cant change size, and as far as i know, they only vent through the filler cap, so it's unlikely to be trapped air.

    The only thing i can think of is that there is more fuel left in the tank when it indicates just above the red mark than there was when you first bought the car.

    I guess you could try dipping the tank, or weighing the whole car, but with no data from 3 or 4 months ago it'd only be guess work.

    Have you always used the same fuel station? When were their pumps last calibrated?
    OT, but any car from the past decade or so doesn't vent through the filler cap - it's bad for the trees. Vapours get trapped somewhere and fed into the inlet manifold when the engine's hot, commonly using a canister of activated carbon

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