Ok here is the description of the latest carb problem I am experiencing.
As background, I recently rebuilt my ZS175s (stock carbs on a 76 TR6).
The air pump and egr valve are removed from this car (and have been for
many years prior to the rebuild - not sure if this affects the carbs at
all but I though I'd mention it).
The problem is a lack of rpm reduction _sometimes_ when I open the
throttles with the pedal. It just stays at high revs. This weekend I
rebuilt the linkage and it now works tons smoother than before. Although
this could be the cause of the problem I fear my problem is somewhere
else. Now when I drive the car for a while (ie. well _after_ the point
at which the temp gague has reached "normal"), I can stab sharply on the
gas and it will just stay at the high revs. The linkage seems to recover
to the pre-stab position. Does this sound like by-pass valve problems?
The Bentley manual lists three causes for "lack of engine braking".
- sticky throttle
- faulty decelration by-pass valves
- faulty ignition retard unit
Now, when doing the carb rebuild, I was a little over anxious and took
apart the deceleration by-pass valves. I had the gaskets from the Moss
kit so I thought maybe I would replace them. Of course when I took the
things apart, I lost the setting for the spring/diaphragm in the by-pass
valves. Although there is a description in Bentley on how to reseat the
valves, I cannot duplicate the described behavior on my car.
Here is what Bentley says: Warm up the car to normal and pull the vacuum
hose off the retard unit on the distributor. The revs should increase to
1300 (from the original 800-850 at idle). Mine go up to only about
1000-1100 if this is a clue. Anyway, you then turn the adjustment screw
on the by-pass valve clockwise until the revs shoot up to 2000-2500
which menas the valve is unseated and floating. I cannot get this
behavior no matter how much I turn the screw. It just stays at the same
idle (1000-1100). I don't think I broke the by-pass valves when I took
them apart I think I just threw them out of adjustment (new ones are
$$$).
So has anyone successfully re-set these by-pass valves? Any ideas?
Also, how does one test the vacuum advance/retard on the distributor? I
can't find this in Bentley or Haynes.
Thanks in advance!
Peter Zaborski
76 TR6 (CF58310 UO)
Calgary AB Canada
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