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From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Help!  I'm trapped in Kalifornia and can't get gas in my 
Date: Fri, 07 Oct 2005 14:18:00 -0400
Message-ID: <>

On Thu, 6 Oct 2005 22:08:32 -0400, "Jon Porter" <>

>"Hunter" <> wrote in message
>> They told me it was because I topped it off.
>Wow. From what I have seen of fuel tanks, there is an expansion area
>("bubble") above the useful part of the tank that is supposed to allow for
>expansion without the fuel coming back out of the cap. Even it it was filled
>to the cap. I suppose that it is possible that the diesel expanded enough to
>force it's way through the cap, but that would be a lot of expansion.

You're correct, Jon.  It has been a federal regulation for >20 years
that domestic car and light truck tanks have sufficient airspace to
prevent overflow.  The clue is her previous sentence, that she parked
on a hill.  Gotta wonder about the logic that goes from parking on a
hill to overfilling causing the resulting overflow....

Had the cap been properly attached, the fuel would not have leaked out
even if it backed up the filler pipe.  Though diesels don't have to
have evaporative emissions systems, they do have to have no-spill
provisions on their tanks.

To address another misconception, If fuel does back up into the EEC
system, it will not do any damage.  All systems have some sort of
surge tank/mist separator to prevent liquid gasoline from reaching the
charcoal canister.  On my Z the tank is under the right rear shock
tower.  In my caprice it is above the gas tank under the floor.

Even without gross overflow, normal sloshing combined with the normal
outgasing of the higher volatiles (propane and butane for instance)
causes misted flow into the EEC system.  The separator is there to
handle these normal occurrences.


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