Hi 6 Packers,
Sorry in advance for the long post :-).
I'm trying to diagnose a problem with my choke operation. Perhaps some one
can shed some light on this. Car is a 76 with the stock ZS carbs and my
emission plumbing is gone. Car has run fine with this et up before and the
choke used to work as well so I doubt it's the missing plumbing but thought
I'd throw that out anyway. Onto the problem...
My choke is not working as I would think it should. If I pull it out all the
way when the car is cold, the car will typically not start and if it does,
the idle is less than normal idle speed and eventually (ie. maybe 10
seconds) the car will die. I have to start with choke all the way in and
keep pressing the gas pedal to keep it idling until warmed up. Once warm, if
I pull the choke out it will kill the car in the same manner.
My understanding is that the first part of the choke cam action (ie. until
the detent in the cam contacts the spring and ball) richens the mixture, and
the second part of the action the cam contacts the screw to the throttle
lever and mechanically increases the idle speed. I am not seeing this
increase idle speed when the cam goes into that second range (nor when it is
in the first range).
I have attempted to tune the carbs following Nelson's directions on the
Buckeye site but am so far unable to fix this choke problem. After tuning my
normal drive way idle is around 850.
My plugs appear to be fine after a run. The front 3 are a nice tan almost
tobacco color. The back three slightly lighter but still acceptable.
Some other facts:
- Car usually stumbles from a standing start until revs increase and it gets
going, then it seems to run fine. This stumbling occurs even when fully
warmed up. I am using Pertronix ignition and Magnecor wires FWIW.
- Once fully warmed up, like after a brief highway run, coming to a stop
will see the idle go to 1300-1500 and if I stay stopped long enough (maybe
30 seconds to a minute) the idle will slowly return to almost normal (around
900-950). I did re-set the temp compensators like described in the VTR
article and Nelson's site.
- The idle screw on the front carb needs to be less screwed in than the rear
after a tuning iteration in order for the Unisyn to show balance at idle. I
believe all my hoses are fine. Haven't checked the carbon canister
internals.
- I rebuilt the carbs a few years ago (maybe 3) and the car has run just
fine after that, including the choke. In fact in the 21 years I've owned
this car, this is the first problem ever with the choke.
- The anti-run-on valve operates normally. In ever get run on and it does
click after shut off.
My suspicions are that my mixture is too rich and thus the choke is killing
it by enriching even more. Although I'm not sure if this is even possible by
the amount of enriching the choke provides? If not, what else could be
causing the choke behavior?
And is it possible for the mixture to be too rich at idle only while once
running the mix goes to an acceptable level (as evidenced by the appearance
of the plugs)? I have not checked my plugs after merely idling - is this
worth while? I have access to a Gunson Colortune mixture tuning kit it that
might be worth using.
Any ideas would be greatly appreciated. Thanks!
Peter Zaborski -- CF58310 UO
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