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Sorry, ment to send this also to the list for
other's thoughts.
Scott Suhring
Elizabethtown, PA
'70 TR6
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Content-Disposition: inline
Date: Sat, 21 Aug 1999 22:30:13 -0400
From: scott suhring <suhring@lancnews.infi.net>
Organization: InfiNet
To: Beth and Ken <BethKen@erols.com>
Subject: Re: Bypass valves
References: <00a401beec25$d61e2f00$ddceaccf@public>
Ken:
I'd almost bet your problem is with the by-pass valve. I also
redid the temp compensator and even re-calibrated them
which the manual says you can't do (there is a great write
up on how to do this in the tech session of the VTR, and it
works!). I too still had the high idle after this so moved on to
the bypass valve.
The high idle is caused by either a rip in the valve diaphram, which
are made of rubber and eventually become brittle, or the valve is
stuck open. Either way you will need to rebuild, or some people
suggest just blocking off (i am not one). Does your bypass valve
have an external adjusting screw? If it does, you may want to
try screwing it in which will lower your idle if their isn't a leak/
tear in the diaphram. Another easy test is to remove the bypass
valve (you can do this with the carbs still attached to the
manifold) and tape over the holes with some duct tape. If your high
idle is caused by the stuck open valve or a leak, it will disappear
by just eliminating the bypass channels from sucking air/fuel around
the throttle. If you were like me and tried fixing the problem
by adjusting the high idle via timing and slow idle screw, be sure
to go back to a datum setting before trying this because this may throw
you off with the carbs all out of wack!
In essence, and quoted from the Haynes Tech book, "The by-pass valve
provides a means of limiting the very high manifold depression
which occurs when the engine is in the over-run condition." Thus,
allowing the air and fuel mixture to be sucked into the manifold
around the throttle disk when it is shut (let off of the gas peddle when
running the engine, lets say at 60 mph) when the engine is running,
allowing some degree of engine breaking without relying on only the idle
set of the throttle. This is my best understanding but don't quote
me, I'm still learning!
If you need further help, let me know.
Scott Suhring
Elizabethtown, PA
'70 TR6
Beth and Ken wrote:
>
> Scott;
>
> I rebuilt my stuck (closed) temp. compensators, but I still have that high
> idle/little braking situation. So, I'm thinking about those bypass valves.
> If they are my problem, is it because they are stuck shut, allowing no air
> to bypass, or would it be that they are stuck open (or leaking) allowing air
> to pass when they should be shut?
>
> What is it they do when the car is hot...open or shut?
>
> Thanks,
> ken
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