Hi Phil:
When replacing my original gas tank after my restoration- I remembered NOT
SEEING A TOP VENT!
Well to my surprise- you are absolutely correct- In the Triumph Workshop
MAnual, under Body, Section 5-page 356 the diagram clearly shows a bajo
fitting vent and the beginning of a vent tube.
SO I just went out to the workshop and pulled the trunk cover panel and
examined the 'front side of the tank with fingers and inspection mirror.
There is Absolutely NOT a vent fitting or plugged hole on my fuel tank. In
fact on the right side of the tank (looking from the trunk) there is a
'grommeted hole' adjacent to the tank on the lowest metal panel, so clearly
at one time a vent tube was placed through this 'orifice' on the earlier TR4
body shells- as implied iun the workshop manual and as you suspected..
I examined the cap again and see that 'air' could find it's way thru the
disc slide-to 'allow' the atmospheric pressure to fill the tank with air as
the fuel is consumed. In fact the later TR6's used a vent tube, but the tube
extended forward to the engine bay where it fed into a carbon canister like
the Jensen H ealys did. On 70'sXJ6 and XJS Jaguars, if the system is not
sealed, the pressurized fuel injection system will not function. Reports of
clogged vent lines cause fuel to flood out the carbon canisters and reports
have been made of fuel tanks being 'buckled' due to the lack of venting - as
Atmospheric pressure exerts upon the 'fuel sucked' tanks, weakening the
sides over time to cause weeps/leaks. Our TR tanks are quite solid in that
respect.
So your reasoning is correct for the need for 'vented tanks' on the
pre-emissions cars (My Jensen Interceptor and Jensen GT ( '74 and '76)
BOTH have the emissions vents, carbon canisters etc. Those fuel caps must be
sealed or fuel vapors also escape.
I have noted that when I smell fuel in the shop while walking around the TR,
if I pop the fuel lid- the next few days the oder is much less- Perhaps I am
'depressurizing' the closed system- and then things, as you say 'settle
down'.
I was told by a lister I have the last known 'still alive' TR4 by commission
#. Perhaps the TR4A's (certainly the TR250's did have the emissions equipt;
and, in the LUCAS Tradition (nothing consistent) perhaps I have 'an early
'post vented era' tank.
I know it is the original tank. Until last January the car was never
garaged-and duringthe retiorataion no gas left in the tank- so this was a
'new' Triumph Discovery!
Sherman Taffel
'65 TR4 CT40054L
www.tracltd.org
----- Original Message -----
From: "Phil Ethier" <pethier@isd.net>
To: "Sherman D Taffel" <staffel@comcast.net>; <jmerone@rocketmail.com>
Cc: <triumphs@autox.team.net>
Sent: Monday, September 02, 2002 10:02 PM
Subject: Re: Where's that GAS SMELL FROM ? I know!
> You can seal up whatever you like, but the fact it that your TR4 fuel tank
> is deliberately not sealed. There is a tube which is connected to the top
> of the tank and comes out under the car.
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