Folks,
Over the last couple months I've rebuilt the carbs on
my car, replaced most of the tired ignition
components, replaced all vacuum hoses, etc. The car
has been running great. My only known problem is that
the (new) rear carb float valve sometimes sticks open.
I just got a new set of Grose Jets last week from Moss
but haven't yet installed them.
But since I can't leave well enough alone, I decided
to convert the car to a Pertronix for "added
reliability." Since I still have a stock coil and
ballast resistor, I connected the positive Pertronix
wire to the fuse box, to the open terminal next to the
white 12V wire. I connected the neg side to the coil.
Verified timing at 4 ATDC.
The car ran better than ever for the first drive with
the Pertronix. On the second drive, after sitting in a
drive-thru and watching the temp climb above 3/4, the
car starting idling very rough and slow and eventually
quit. On the way home, it would run fine over 1200
rpm, below that, barely stayed alive. After letting it
sit and cool for a few hours, it started right up and
idled fine. After 5 minutes of driving, idle problem
returned.
So I put the points back in. Reset timing to 4 ATDC.
Problem stays: car drives fine for few minutes then
tries to die on idle. Turn it off and back on and it
starts fine but soon repeats the scenario. I noticed
the car would idle OK with the choke out and had a lot
of popping on deceleration, leading me to believe the
mixture was leaning way out at idle. Pulled the plugs
after it died and confirmed they were very
"white".
With the car idling normally, I pulled the small hose
to the anti-run-on valve from the manifold to hook up
my vacuum gauge. Suddenly the idle problem shows up. I
reconnect the hose, rev the engine -- no change. Turn
the car off and back on - problem fixed. Pull the
hose, problem returns. Restart and pull the hose at
the anti-run-on valve end and the engine speeds up
slightly. Pull the hose at the manifold now and the
engine speeds up. Go for a test drive, car runs fine.
So this makes sense (I think!) -- if the anti-run-on
valve somehow switched and stuck open with the engine
running and ignition on, I would pull a vacuum on the
float chamber but still get a spark in the cylinders.
With a stuck float valve on the rear, I may be getting
just enough fuel through to barely keep the engine
going. When I increase RPM, the pressure differential
in the chamber drops and mixture mostly returns to
normal. Turning the car off and back on would
"reset" the anti-run-on valve, giving me back
the stable idle.
Tonight I will pull the anti-run-on valve and cycle it
manually/clean it and the connections. But my
questions are: how could I trigger this behavior by
pulling the vacuum hose off (did I just jostle the
assembly enough to trip a bad connection)? And could
the way I hooked up the Pertronix possibly have
anything to do with this, or was it just a
coincidence? Anything else I should check?
Thanks,
William
'74 TR6
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