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Thread: Why is my fuel tank getting smaller?

  1. #31

    Default Re: Why is my fuel tank getting smaller?

    Quote Originally Posted by Grizzman View Post
    Don't forget that neither the engine nor the fuel pump need to be running in order to empty the tank.

    True that. However, never siphon gasoline by sucking on the hose with your mouth. Nasty, nasty stuff!

    ~ Chance
    Never point a flashlight at anything you don't intend to illuminate! Never buy a flashlight you have to make payments on.

  2. #32
    Flashaholic* Poppy's Avatar
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    Default Re: Why is my fuel tank getting smaller?

    I agree with all those who said it is most likely the sender or the gauge.
    The sender is like a rheostat (a variable resistor that increases resistance as the float drops in the tank). The increased resistance, reduces the voltage to the gauge as the fuel level drops.

    If you want to trouble shoot the sender, you can check its resistance values when full, and compare it to specs.

    It is quite possible/probable that the sender has increased resistance over the years, it is wearing out.
    You might also have a crappy (high resistance) connection to the sender. Either case will give you a lower gas level reading than what you actually have in the tank.

    -------------------------------------------------
    OK.... now time for a story, if you have time to read it, OR care to

    I had a 32' A class motor home, that we used, to go cross country. That was our ONE big trip. We then used it each year to be a class A limousine, to take the family to Disneyland in Florida, where we didn't stay in the RV, but rather in a hotel.

    So... one year I bring it home the day before we are ready to leave, to clean it up, and load it up. Sanitize the water holding tank, etc.

    It has 3/4 tank. IIRC 70 gallon tank.

    I try to start the generator, and it won't start... damn, that's important or we won't have roof air conditioning, and the cab air isn't enough on a hot day.
    OK... so it starts on carb cleaner. Oh look... squirrels chewed on the fuel line to the generator! Got a new fuel line, but it still wasn't getting fuel. Maybe there is an in-tank fuel pump for the gennie. IDK, but the decision is made to repair it some-day while we are down there.

    I figured... let me top off the tank, it should only take about 15-18 gallons, but let's do it and then go.

    Well AT $2 a gallon, I started watching the pump at $30 ... $35 ... $40... $45!?? $50 ??? WTF??? $90
    Sun of a gun! I was almost out of gas!
    The generator won't drain the tank below 1/4 tank. That is why it wouldn't start.
    With a full tank... the generator started right up.

    I remember being really surprised, during the last stretch home during our last trip, that I was getting amazing mileage.

    Yeah, what happened is that the wire from the sender was also chewed by those furry tailed rats, and snapped at 3/4 tank.

    So here's the deal.
    The gauge will typically stay where it was when you disconnect it/break the sender wire.
    IF you short it, it will go to FULL tank.
    I don't know what the resistance should be for EMPTY. It may vary with the gauge.
    Last edited by Poppy; 05-04-2016 at 09:54 AM.
    My Grand Kids call me Poppy

  3. #33

    Default Re: Why is my fuel tank getting smaller?

    Face,

    Did you find what was causing the problem?

    ~ C.G.
    Never point a flashlight at anything you don't intend to illuminate! Never buy a flashlight you have to make payments on.

  4. #34
    Flashaholic* Ladd's Avatar
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    Default Re: Why is my fuel tank getting smaller?

    I was wondering the same thing. Be nice if the OP could update......
    Thanks, CPF!

  5. #35

    Default Re: Why is my fuel tank getting smaller?

    Me three.

    bob

  6. #36
    Flashaholic* mcnair55's Avatar
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    Default Re: Why is my fuel tank getting smaller?

    Me four
    Alkaline collection Energiser-Duracell-Ansmann-GP

  7. #37

    Default Re: Why is my fuel tank getting smaller?

    X5....
    John 3:16
    "The only friends I have from France are french fries" -PK

  8. #38

    Default Re: Why is my fuel tank getting smaller?

    Hi everyone,

    Sorry for not getting back to you sooner, but I had forgotten that I had posted in this forum; I had posted in quite a few out of desperation :-)

    Since I posted the issue had persisted with the appearance of a smaller fuel tank.

    However, with the last few refuellings, amazingly, everything seems to be back to normal and as it was before the mystery started.

    I have no clue as to the answer to the puzzle, but I have noticed that I no longer get the "rushing" sound when I release the fuel cap on the last couple of fuellings.

    Thanks once again to you all for taking the time to reply and please accept my apologies for the delay in replying to you all.

    Enjoy the rest of your weekend.

    Face
    I am actively seeking employment in the Norfolk/Suffolk area of the UK. I have good IT and communication skills, with 18 years of print experience. If you can help me in any way, please send me a PM.

  9. #39
    Flashaholic*
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    Default Re: Why is my fuel tank getting smaller?

    Quote Originally Posted by Face View Post
    Hi everyone,

    Sorry for not getting back to you sooner, but I had forgotten that I had posted in this forum; I had posted in quite a few out of desperation :-)

    Since I posted the issue had persisted with the appearance of a smaller fuel tank.

    However, with the last few refuellings, amazingly, everything seems to be back to normal and as it was before the mystery started.

    I have no clue as to the answer to the puzzle, but I have noticed that I no longer get the "rushing" sound when I release the fuel cap on the last couple of fuellings.

    Thanks once again to you all for taking the time to reply and please accept my apologies for the delay in replying to you all.

    Enjoy the rest of your weekend.

    Face
    As is usual, when a person does not understand problem, there are usually two or more problems...

    1. The 'rushing sound' is an important clue. Actually, I had somewhat the same 'rushing sound' on my 1998 Honda Civic 1.6L manual xmsn, 50+ mpg highway, 40+ mixed, 220K miles at time of sale. still with original clutch.

    In my case, the 'rushing' was an outflow of fuel vapors from the gas tank immediately upon opening the gas cap, soon after the engine had been switched off. meaning that the tank was pressurized even after the engine was switched off, at least overpressurized for a while. After being parked overnight, there was no over-pressure in the fuel tank. This overpressurization occurred most of the time when the ambient temp changed sharply during the course of driving the vehicle or the vehicle had been driven long distances. The excessive over-pressurization is not a correct condition.

    The EVAP system is supposed to control excess fuel vapors by directing the fuel vapors from the gas tank to the ORVR canister in the engine compartment. The ORVR canister is filled with activated carbon. The trapped fuel vapors are then released into the intake manifold to be burned in the engine.

    In the case of my 1998 Civic, the activated carbon in the filter was collapsing as well as the tubing between the gas tank and ORVR canister was partially blocked (unknown why). Which is why the overpressure slowly released over time w/o opening the gas cap.

    Why did the OPs situation improve? another poster commented that old petrol will congeal on various surfaces. That would fit the situation with the activated carbon filter or tubing leading to the OR.

    2. Ref fuel gauge questions: There are too many fuel gauge types to take a remote guess at this. Here is a short simple tutorial on fuel gauges.
    Last edited by moldyoldy; 10-19-2016 at 07:21 AM.

  10. #40

    Default Re: Why is my fuel tank getting smaller?

    I have a 2002 VW Jetta TDI and get an average of 55mpg.

  11. #41

    Default Re: Why is my fuel tank getting smaller?

    The electrical system or float are the two most likely causes.

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