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over-filling the gas tank

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Michael Oritt said:
Roger--

My 100 gives me 22-24 mpg consistently and at 200 miles on the tripmeter I am looking for a gas station. My wife's 3000 consumes a bit more and my limit of comfort with it is 180 miles.
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Michael,
Good for you.
My point is my mileage varies so much, and others may too, that a wise man in our situation, does not rely on the tripmeter to determine if he has gas in the tank or sitting on the side of the road waiting for help/gas.

Drive it like you stole it! (till you run out of gas)
Roger
 
AUSMHLY said:
....He questions the gas cap. Is it an original BJ8 cap? Is it a good reproduction? Is it a working cap?...
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This could be the problem. Cap *looks* fine, screws on, stays on etc. I suspect it is a Moss replacement of the original if it is not the original. But now that you mention it, it sure seems like a good cap should be able to deal with this issue. Any ideas on what a visual inspection or other test of the cap should show me?

BTW Roger, I wonder if those 12 mpg involve lots of idling in rush hour/typical CA type traffic. It seems awfully low unless you are burning rubber from each stop. You know, driving it like you stole it.
 
Roger may be on to something. If the rubber gasket is torn or not seated proberly you may get some out flow. The rim of the pipe may be bent too. Good time to get a locking cap in this economy. I've always been told to buy gas in the mornings before it expands form the days heat. Your got more for your buck. But I don't believe gas expands more than 5% in volumn. Course that was the old gas before all the crap they add (ie, ethonal, oxygenation).

Sorry, Roger, I get 17 to 18 city and 23 hwy.But I have to run lean up here at 6500 ft. Must be those heavey chrome nuts on the block. (Don't shoot me, just a little joke). But that is another subject that has been done.
 
TomFromStLouis said:
Twice now I have filled my BJ8 gas tank, drove the half mile home and parked it. Next warm day there is gas seeping from the tank cap. What appears to happen is that the gas expands as it warms to ambient temperature from whatever temp it was at the station.

The first time was a "HOT DAY"it percolated and bubbled out when I removed the cap. :yesnod: Because there is no overflow vent in the Healey tank except via the vent in the gas cap or seeping past it's rubber seal when the contents of the tank expands. Perhaps some air was trapped somewhere in there too possibly caused by too high fuel flow rate from the station pump.

Obviously I am putting too much gas in, :yesnod: :yesnod: although I just let the dispenser shut itself off and I do not top off.

Does this happen to you? :yesnod: If I over fill and it is a HOT DAY and the car is not driven much and is also parked out side.

Any ideas on how I can prevent it other than driving a few miles after each fill-up? :yesnod:
put less fuel in the tank only enough for your immediate driving needs and do not rely on the dispenser auto shut off. My parking spot is level.

OH do not forget to carry a calibrated stick or SS rod in tne boot--- :laugh:
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The thermal expansion of gasoline is more than adequately covered on the web Just Google "Thermal Expansion of Gasoline.
 
TomFromStLouis said:
Twice now I have filled my BJ8 gas tank, drove the half mile home and parked it. Next warm day there is gas seeping from the tank cap. Perhaps some air was trapped somewhere in there.
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Fluids are incompressable - which means they do not expand.

The expansion comes from, when you overfill the tank there will be some air left in the tank. As the air gets hotter, some of the gas will vaporize into the airbubbles in the tank, causing it to overflow.

The best trick here is to not fill the tank on you 6-cyl up to the top of the neck. Only maybe a 1/4 or half way up is enough to stop it from spilling over.

By the way I have one of those repro lockable aston caps on there, and it definitely works wonders to keep the gas in.
 
I am beginning to think that maybe my parking spot is not as level as I thought. Perhaps a wee bit of air gets trapped in the tank and it is that air expanding that causes the overflow. Looks like I need to park on a different angle or burp the tank before bedtime.

Thanks all for your input.
 
HI Tom, if your car is parked on a slant so that the fuel tends to collect at the end of the tank where the filler tube connects this will enhance the overflow problem. Burping the tank after gassing up may release the trapped air inside.--Keoke
 
:smile: Hi Tom. If you attended the European car show 2 years ago you might remember that I too had that exact same thing happen to me. I had just filled up the tank about 7 miles from the show. Drove to the show and had to park on a slight incline with the gas filler side downhill. It was a warm day. After about an hour I started to smell gas and there it was pouring out of the cap! I removed the cap and the gas receded, but started up again when I replaced the cap. Unfortunately I was blocked in and couldn't pull out and leave the show. I had a new Bentley within inches of my rear bumper, and a Ferrari about 2 feet in front of me. Very embarrasing. A friend came over and offered to help. He said replace the cap and rock the car side to side, you have an air bubble in the tank. I did what he said and guess what, it worked! :banana:
 
healeynut,
liquids are not compressible, I'll live with that, however almost all materials have a coefficient of expansion in relation to temperature and atmospheric pressure
 
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