On Sun, 11 Oct 1998, John Middlesworth wrote:
> I've noticed that the gas tank in my 1966 TR4A has no tube to vent fuel
> vapors out under the car, as I understand the original design to work.
> I'm guessing that it has a TR6 tank in it, which wouldn't be bad if the
> gas tank vented the vapors out. So my question is--does the 4-4A cap work
> that way (or does any TR's cap work that way)? If, as I suspect, it
> doesn't, then what problems should I expect with a tank that has no real
> way of venting fuel vapors? Should I attempt to retrofit a TR6 carbon
> canister to this tank?
If you have an airtight tank then you will experience fuel starvation. I
think the stock TR4-4A gas cap has a 2" o-ring to seal the cap. My tank
has a vent tube (originally a banjo bolt, now a hydraulic fitting :-))
that comes off the top of the passenger's side of the gas tank and pokes
down thru a hole in the body.
I think the only real way to test is to try running with the gas cap
'open' if you experience fuel starvation. If it goes away then you've
found the culprit.
To my knowledge the TR6 gas cap is vented. You shouldn't need to install
a carbon canister, as I don't think there is a vapor return line from the
carbs (could be wrong tho!!) on the TR4A. Just a gas cap.
-Malcolm
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