[DeTomaso] gas tank question

Art Stephens artstephens at charter.net
Sun Sep 2 01:43:43 EDT 2007 

Chris,
     I'm not sure what your roll over valve looks like but unless I am 
missing something,  it is the vent for your tank.  It allows air into and 
out of the tank.  The only time it should close is when it is upside down. 
If your tank was not vented,  you couldn't draw fuel from it.  And 
theoretically,  if the fuel was heated enough,  it would probably burst the 
tank,  if the tank was not vented.  You are correct,  fumes should be coming 
out of that vent. The car originally had a vapor recovery system that 
included a carbon filled canister mounted on the right side of the engine 
bay. The vent line for the tank ran to the canister.  Some guys have done 
away with the canister and simply vent the fumes to the atmosphere thru a 
hose.  Note that if you overfill the tank,  fuel will come out of the 
rollover valve/vent,  that is unless your car is upside down :-))   That is 
why I recommend the vent line either run to the canister, if it still exists 
in your car, or make sure that vent line empties some where away from a 
possible ignition source.  I don't fill my tank to the top any more to avoid 
the problem.

Art


----- Original Message ----- 
From: "Christopher Kimball" <chrisvkimball at msn.com>
To: <artstephens at charter.net>; <detomaso at realbig.com>
Sent: Saturday, September 01, 2007 8:18 PM
Subject: Re: [DeTomaso] gas tank question


> Dear Art,
>
> Thanks for the info.  As soon as I moved the car into the garage there was 
> no more gas leakage.  The drips were running down the side of the tank on 
> the tank side of the heat shield, so unless it started squirting over the 
> top of the shield, which is very unlikely, I should be OK even if it does 
> it again.  The amount escaping was very small.
>
> As far as blowing into the vent tube, I don't think that would work, since 
> the little ball would prevent any pressure from releasing--that's what 
> it's designed to do, anyway.  I'd have to remove the little hose with the 
> pressure ball attachment to get any pressure coming back out the tube once 
> I blew into it.
>
> An idea I might try is to extend the tube so I can position the pressure 
> ball tube pointing upward.  I think that would still allow the air to pass 
> into the tank as the fuel gets used, plus, since the ball wouldn't be in 
> the "seal" position, air should be able to pass both in and out of the 
> tank.  If I flipped over, the ball tube would then be inverted, the ball 
> would roll to the other end of the tube and seal it, preventing gas from 
> running out.
>
> The only concern I have with that idea is that if the tube is pointing up, 
> that effectively means there is a little tube open to the outside world 
> from the gas tank.  Wouldn't that cause the gas to slowly evaporate, or 
> cause dangerous, flammable fumes to be released into the atmosphere?
>
> I appreciate your help.
>
> Sincerely,
>
>
> Chris
>
>
>>From: "Art Stephens" <artstephens at charter.net>
>>To: <detomaso at realbig.com>
>>Subject: Re: [DeTomaso] gas tank question
>>Date: Sat, 1 Sep 2007 17:48:13 -0700
>>
>>Chris,
>>      Make sure you blow on the vent line and not the fuel pick up line as
>>that could start a siphon effect which could be very bad indeed!
>>
>>Art
>>
>>
>>----- Original Message -----
>>From: "Art Stephens To: List-Subscribe:"
>><artstephens at charter.netdetomaso@realbig.comhttp://list.realbig.com/mailman/listinfo/detomaso>;
>>"Sender: detomaso-bounces at realbig.com"
>><mailto:detomaso-request at list.realbig.com?subject=subscribe>
>>Sent: Saturday, September 01, 2007 5:38 PM
>>Subject: Re: [DeTomaso] gas tank question
>>
>>
>> > Chris,
>> >     You might want to make sure you don't have a leak in the fuel pick
>>up
>> > line.  If you have a leak in the line going to the fuel pump, while the
>> > engine is running,  that would be bad!  I would keep a fire 
>> > extinguisher
>> > handy whatever you do.  I would check to see that the tank vent is
>> > working.
>> > you could probably do this by hooking up some clear tubing to the roll
>> > over
>> > check valve.  You could blow on the tubing and see if air will flow 
>> > into
>> > the
>> > tank.  If you blow on it enough,  you should be able to feel air
>>pressure
>> > come back thru the tube which would let you know that the vent is
>>working.
>> > So,  you could blow on the tube then cover with your finger, then blow
>> > again
>> > and continue till you feel pressure come out the tube.  The gas cap
>>should
>> > be on when you do this.  It doesn't sound like you have done anything
>> > wrong.
>> > The fuel probably expanded due to the heat,  and reached the level 
>> > where
>> > it
>> > started coming out the vent?  You may also want to check and see that
>>the
>> > screws are snug that hold vent and fuel line assemblies at the top of
>>the
>> > tank.  I would blow on the tubing with my lips and not compressed air,
>> > you
>> > don't want to blow the tank up!  I would imagine it will stop leaking
>>when
>> > it cool off this evening or when you run the fuel level down.  You
>>should
>> > have tubing on the vent line,  running some where safe,  in case you
>>ever
>> > overfill again.  You don't want that fuel dumping onto something hot!
>>Let
>> > me
>> > know if you have any questions and be careful!  I wouldn't start the 
>> > car
>> > until the leaking has stopped and it has passed these tests.
>> >
>> > Art
>> >
>> >
>> > ----- Original Message -----
>> > From: "Christopher Kimball To: detomaso at realbig.com List-Subscribe:"
>> >
>><chrisvkimball at msn.comhttp://list.realbig.com/mailman/listinfo/detomaso>;
>> > "Sender: detomaso-bounces at realbig.com"
>> > <mailto:detomaso-request at list.realbig.com?subject=subscribe>
>> > Sent: Saturday, September 01, 2007 3:41 PM
>> > Subject: [DeTomaso] gas tank question
>> >
>> >
>> >>I have a recently coated and refurbished gas tank in my '72 which was
>> >> installed in January.  Today I filled the tank (probably more full 
>> >> than
>>I
>> >> should have) and as I was dusting off my car in the warm sunshine, I
>> >> noticed
>> >> gas dripping onto the driveway.
>> >>
>> >> I checked, and I saw that gas was seeping out of the top of the tank
>>both
>> >> where the fuel line comes out and where the air-vent is located.  On
>>the
>> >> air
>> >> vent I have just a short tube with one of those "ball in tube" safety
>> >> deals
>> >> so air can go into the tank, but gas can't come out of it if I ever
>>flip
>> >> over.
>> >>
>> >> It occurred to me the heat was obviously causing the gas to expand and
>> >> since
>> >> the fuel cap is sealed, there would be nowhere for the gas to go, 
>> >> other
>> >> than
>> >> force its way out via the path of least resistance.
>> >>
>> >> I put the car in the garage where it is much cooler, wiped the gas 
>> >> from
>> >> the
>> >> top of the tank, waited to be sure there would be no more seepage and
>>ran
>> >> a
>> >> bead of gas-resistant silicone rubber around both the fuel line
>>connector
>> >> and the air vent connector where they attach to the tank, to seal 
>> >> them.
>> >>
>> >> I then realized that if the same situation happens again, gas will,
>>once
>> >> again want to go somewhere, and perhaps the new path of least
>>resistance
>> >> will be something worse!
>> >>
>> >> Did I do the right thing by sealing the seepage, or have I done
>>something
>> >> really dumb?  Is there some sort of gas cap that would help this
>> >> situation?
>> >>
>> >> I'm hoping to drive to Seattle tomorrow for a car show, about an hour
>> >> each
>> >> way, and I don't want to go up in flames!!!
>> >>
>> >> Thanks,
>> >>
>> >> Chris
>> >>
>> >> PS:  I also noticed the fuel line runs down the engine bay to the
>>bottom
>> >> of
>> >> the engine, passing within inches of the headers, which get HOT, so I
>> >> covered the hose with that silver-on-one-side,
>> >> sticky-black-goo-on-the-other
>> >> side heat shield stuff.  It may not help, but I figure it couldn't
>>hurt!
>> >>
>> >>
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