Message text written by "Jay Snavely"
>I am still trying to figure out why my rear carb on my stock 74 TR6 leaks
gas when the car is not running. After looking thru the E-mail archieves,
I
think the problem may be in the emission system. My gas tank builds up
pressure inside, even when the car is not running for days. If I relieve
the pressure, the leak stops. I've already replace the jet with Grose jets,
checked the float, and checked the float height. From what I read, there
should not be any pressure in the tank. Does everyone agree with this? If
this is true, I guess there must be some blockage in the vent line between
the tank and the carbon canister. I see there is a small expansion tank in
this line, above the tank. Does this tank have any valves in it which
might
be stuck? Any ideas on where I should look first? As far as I can tell,
all the emission parts are intact and attached properly. Thanks for any
help.
Jay
74TR6
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Jay,
When I bought my 71 TR6 I found I had a similar problem. Mine manifested
itself by drawing a partial vacuum on the tank while running. The first
time I ran the engine I heard a pop like sheet metal "oilcanning: after a
while. Soon there after the engine stopped. Checked for gas and found
none. When I opened the filler cap there was a great equalization of
pressure and the tank "popped" back.
Further investigation revealed that the plastic vent line had come to rest
on the exhaust system and had melted to the point of blocking off the ID
altogether and drawing fuel from the tank resulted in a vacuum situation.
I trimmed off the melted part of the line and the car has run fine for the
last 15 years.
You may not have the same problem as I had but you definately have a
blockage in the vent system. You can trouble shoot this through the
process of elimination. Does the problem occur if you leave the filler
open (most likely not). What if you pull the line loose from the charcoal
canister (convenient to get to)? If yes then the problem is in that line.
If not then the canister is the problem.
If the former is the problem (line) you will have to trace the line from
the top of the tank, through the vapor separator, down under the car along
the frame rail to the front to the charcoal canister.
Good luck hunting
Dave
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