[T3] Mysterious squareback condition.... need suggestions.

[Dave Hall]

Check both carbs have the choke heater wires connected firmly - they can
fray with engine vibrations over time - and operate correctly.  If one is
fully closed and the other opening properly, you will get very uneven
running.  (Assumes you still have the autochokes functioning, not disabled
and set permanently open).

Another twin carb problem is if one of the balance pipe connections is loose
and causing an air leak.  That will cause a similar fault.


Dave.
UK VW Type 3&4 Club
===================

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of James
Lingenfelter
Sent: 26 January 2011 00:42
To: type3 at vwtype3.org
Subject: [T3] Mysterious squareback condition.... need suggestions.

   I have a '68 squareback, with dual Weber 34ICT carbs. My wife drives it
much more than I do. About 6 weeks ago she called me saying it had started
running poorly on her way home from the store, felt like it was missing,
started backfiring, etc. She got a block from home and it died and would not
restart. When I got home I looked at it and saw nothing other than the coil
wire being slightly loose.  
After pushing that back on, it started immediately, idled perfectly, I took
it for about a 45 minute test run and it ran absolutely perfectly. I
determined either the coil wire had been coming off, or either my wife was
going nuts.
   We continued driving it over the last month with no problems whatsoever.
Then yesterday, my wife was taking it to the grocery store..... she said it
was hard to start, then ran horrible leaving home, so she immediately came
back and parked it. She tried later in the day to start it and couldn't.
When I got home from work, I got it started after much cranking and pumping
on the gas, but then it idled horribly and would die within 30 seconds if
you let off the throttle.  
And I witnessed it backfire once through the passenger side carb when I
opened the throttle from the engine compartment. From randomly inspecting
things in the engine compartment I discovered massive corrosion at the plug
wire connections to the distributor cap..... I was already planning to
replace them since one plug wire had shocked me through the shielding
recently. I consulted with my brother, who's an auto mechanic, and
determined that, considering the all-day rain we had yesterday, that I
indeed had an ignition problem probably resulting from poor connections or
arcing somewhere.
   So, today I replaced the distributor cap, rotor, and plug wires.... It
started immediately, idled OK; I let it idle in the driveway about 15
minutes, then took it for a shakedown run. I drove about 5 minutes, and
suddenly without warning, it felt like it was running on two cylinders.....
not even three, but TWO. Barely enough torque to let in the clutch in any
gear without killing the engine. I let off the gas and it idled very slowly
and lopsided, and was destined to die.... I revved it, it sounded ok again,
and I pulled over the first decent place I came to. I shut it off for a few
minutes. It restarted easily, and ran fine coming back home.
   So this is where I'm at now. I've now witnessed what my wife has been
trying to describe, and I have no idea what it is. Fuel pump is good,
recently replaced fuel filters; intake leaks that plagued me forever are
permanently fixed.... I maintain this car pretty obsessively since it's a
daily driver. Could it be a carb issue?  
Sorry this message is so long, but I thought I'd relay every detail in case
any of it helps. Any clues or suggestions will be greatly appreciated!
   Thanks,
    Jimmy

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