can gas overfill cause fuel gauge sensor to not work ?

<div class='quotetop'>QUOTE(smokey1 @ Jul 9 2007, 08:18 PM) [snapback]475951[/snapback]</div>

The one time I really overfilled, I got over 200 miles before the first pip disappeared.

Dave M.

 

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<div class='quotetop'>QUOTE(catgic @ Jul 10 2007, 05:44 PM) [snapback]476423[/snapback]</div>

I just want to make you aware that filling the tank to the tippy-top may result in damage to the charcoal evaporative emissions canister. I'm not sure at what level the damage starts to occur, but there have been a few posts (at least one by galaxee, I think) about the discovery of damaged charcoal canisters due to overfill.

For me, I stop fueling at the first click-off. If I'm only putting 10 or 9 or 8 gallons in, I'm OK with that. Obviously, you're free to make your own choice, but I just want to make sure you're making that choice with all of the information.

 

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<div class='quotetop'>QUOTE(catgic @ Jul 10 2007, 06:24 PM) [snapback]476439[/snapback]</div>

How can you be sure you started with an "empty" tank when filling with 11.9 gallons (unless you've run out of gas)? I would rather play it safe and fill to the first click. You're getting so many more miles per gallon, you don't have to fill up often anyway.

 

<div class='quotetop'>QUOTE(catgic @ Jul 10 2007, 06:24 PM) [snapback]476439[/snapback]</div>

I don't know what the "tippy-top" means relative to the 11.9 gallon gas tank capacity. HOWEVER, filling the tank to 11.9 gallons may, at certain times, be overfilling the tank. What do I mean by "at certain times"? Well, when the temperature is cold out, the bladder shrinks a bit so the true capacity of the tank/bladder is not 11.9 gallons. I would go as far as to say that the car's tank does NOT have a capacity of 11.9 gallons. I would say that the tank capacity is variable (depending on temperature, mostly), and 11.9 gallons is typically the maximum capacity.

You say: "I assume that one can fill the tank/bladder to the spec'ed 11.9 gallon level without "damaged charcoal canisters" occurring." I think that is a bad assumption and you could get into some trouble by assuming that. I agree with you that filling to 8-10 gallons is underfilling the tank. However, there are no bad consequences from underfilling the tank, which is not true for overfilling the tank.

Moreover, as SaxyBiz points out, how do you *know* how much gas is in your tank when you pull up to the gas station? If you're using the MFD to calculation, some people have pointed out that there is often a slight discrepancy between the computer-calculated mileage and the long-term "hand" calculated mileage. It is, usually, a quite small discrepancy, but it's enough for me to say that you probably don't know how much gas is in your tank to the nearest 1/10th.

There are many sides to this argument, as you will find out if you've searched the board. I am clearly at the "safe" end, in that I stop filling once the pump clicks off for the first time. I'm sure that I could continue to fill for a while and cause no damage to the car. However, what I'm not sure of is how long I could continue to fill without causing damage.

 

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<div class='quotetop'>QUOTE(catgic @ Jul 10 2007, 06:24 PM) [snapback]476439[/snapback]</div>

The bladder is, indeed, funky. What you wrote (above) is true with most cars...but, due to the design and presence of the bladder, the 'full' capacity of the tank actually does vary.

You'll probably not get 11.9 in there all (or even most) of the time, and ---due to this--- there is a chance that forcing the issue in search of a 'full' 11.9 gallons might damage the cannister...since the tank's *actual* capacity at that moment might be less.

The gas gauge is weird, too, and it has been reported that resetting it can sometimes help with the "guess gauge" issues (240 miles before a pip disappears?)

Just fill it up 'till it clicks, maybe make one more attempt...but once you're close to what full should be, just stop. Who cares if you get an extra gallon in there, anyway? To me, it's not worth chancing damage to the car.

 

<div class='quotetop'>QUOTE(catgic @ Jul 12 2007, 05:39 PM) [snapback]477773[/snapback]</div>

You clearly have done some research and thought about this hard, so you're well-equipped to make your own decision. As you pointed out, the real damage can occur when gasoline is forced up into the canister under pressure. People (including myself once) have overfilled the tank by filling to the first click-off, then starting to pump again. In my case, the car spit a couple cups of gasoline back out of the filler neck after I stopped pumping, suggesting that the liquid gasoline was under some pressure in the tank. I imagine that I forced some (liquid) gasoline back up into the charcoal canister. The general understanding of the issue seems to be that if you do that type of thing once or twice, you're not going to cause much damage. On the other hand, if you do it more often, you could run into problems. I agree that there is no clear cause/effect case of failing charcoal canisters. However, there is some anecdotal evidence and I guess I'm just playing it safe.

I'd say that if you never have the problem with the car spitting gasoline back out of the filler hole and if you can never see any gasoline down the filler neck, you probably won't cause canister damage. We don't drive a huge amount (we've had the car for 1.75 years and only have ~16K miles on it), so I don't mind having "partial" fills. Yes, it means that I have to go to the gas station more often, but it's still only once every two weeks, or so.

 

I *alomst* had my first burp last weekend. The one little additional
bit of fill I usually do after the first clickoff seemed to be taking
much longer than usual, so I stopped and let things settle and then
carefully started pulling the nozzle out to look. A tiny bit of
gas dripped onto the rubber collar and it seemed to be full right
up to the neck, and maybe wanting to rise out of it. Aieee! I
stuffed the nozzle back in to help seal that off, and shook the car
around again to try and eject any trapped air -- yes, that seems to
help during fills and get remaining vapor over to the correct tube
toward the canister. Pulled the nozzle again and the level was
still visible, but stable. With some degree of relief mixed with
trepidation I replaced the cap without any real spillage. And then
took a half-hour tool around the surrounding countryside to run some
of that off before it could potentially go through an expansion
cycle the next morning.
.
But this is the first time the gauge didn't drop the top pip until
over 200 miles. I've never filled it that high before, and it *was*
only because of a defective pump nozzle shutoff that didn't. But to
possibly answer the OP question, my gas gauge seems to still work..
.
_H*

 

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I never knew it was wrong to over fill your tank I have 2 bars left & reads 100 miles & fill up with 6 gallons