<VV> Help - Convention Attendance at Risk!

[Joel McGregor]

It sounds like a bad gas cap to me.  It's forcing the pump to pull a vacuum in the tank.  By the time you pull over the vacuum has been relieved enough to allow it to make fuel pressure again and run.  Try driving it with no gas cap. (not a new one or different one)
Joel McGregor
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From: virtualvairs-bounces at corvair.org [virtualvairs-bounces at corvair.org] On Behalf Of Jeffrey B. Aronson [jrh at foxislands.net]
Sent: Wednesday, July 11, 2012 6:55 AM
To: Virtual Vairs
Subject: <VV> Help - Convention Attendance at Risk!

Sorry in advance for this long email, also a post on the Corvair
Center/Corvair Forum!

I'm having a long stretch of continued running problems with my '66
Monza 110/4; now it's making my attendance at the Convention questionable.

The core symptoms are that the car will start and run quite well for
approximately 15 minutes - nice idle, smooth acceleration, good power -
and then cease to accelerate. Pressing the throttle to the floor will
result in a tremendous "bogging."

The only way to pick up and hold speed is to feather the accelerator to
slowly build speed. The car doesn't just slow down, it wants to die off
the side of the road. Unless the car sits for a few hours it will not
run well again. It will tootle about town fine - it only manifests
itself when it's under load at speed. When it has died, it will sputter
to a stop. Then it will start again. A mechanic on the roadside has seen
the carbs shoot gas when punching the accelerator - so have I.

The car has 129,000 miles on it. I've had the car since 2007 and have
put about 15,000 miles on it since its purchase. It did not exhibit
these symptoms until the past year.

A leak-down test yesterday revealed no cylinder blowby in any cylinder.
All the plugs looked the same - dry and a bit black from running around
town too often - both to me and more experienced Corvair enthusiasts
[thank you Dirigo Corvairs].

I've tried to tackle this in sequence to diagnose the problem
effectively, to determine whether the problem is fuel or spark, or some
combination of the two. Here's what's been replaced [so far to no avail]:

-New spark plug/coil wire set [Clarks]
-New coil [Clarks]
-Rebuilt distributor [Clarks]
-New points, cap, rotor, condenser (replaced twice) [Clarks]
-New engine wiring harness [Clarks]
-Rebuilt carbs [Clarks]
-New fuel lines from sending unit to carbs
-New filter sock
-In line fuel filter
-New fuel lines in engine compartment
-Replaced Facet electric fuel pump twice, then removed the pump altogether
-Replaced mechanical fuel pump twice, now running only on mechanical pump
-Gas tank drained examined with scope and pronounced clean
-Filter stones completely clean
-Carbs balanced and synchronized by an experienced tuner and confirmed
by a Unisyn.
-Exhaust "doors" open when the car is warmed up
-Placing my hand over each carb throat when running results in the same
drop in rpm.
-Running the car at speed without a gas cap does not change the running
problems.
-Balance tubes, vacuum hose and PCV pipe are fine and the PCV pipe has a
tiny orifice at the vacuum hose end. It runs the same with and without
that orifice.

Since the car starts and fires I can confirm that I have spark, low
tension and high tension. On the side of the road the car will restart.
Cracking a fuel line at the carb shows that I do have fuel pressure in
the lines.

The coil is in the stock location and has been there since I purchased
the car. The coil's been replaced twice with no change in running
condition. The coil was hot to the touch yesterday when I experienced
the problem again - but it's always been hot after running. When last
tested it had the correct voltage when running.

The car does run around town without these symptoms - the problems seem
to be when the car is running warm [> 10 minutes] and under highway
speed load.

The car needs to earn its keep as a work vehicle [4 hours of driving
once a week] and I want to keep my reservation and registration at the
Convention. Has anyone else experienced this problem and discovered a
solution not on my list?

Thanks for your advice,

Jeff Aronson
Vinalhaven, ME 04863
www.landroverwriter.com
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