[T3] Leak Down Test and Rich Running

Thu Nov 3 16:12:01 PDT 2011

Ill bet the resistor in that spark plug connector has burned open.

Keith

Top Notch Restorations
topnotch at nycap.rr.com 
http://www.a383ina68.addr.com/radiorest/main.htm
71 Squareback "Hothe"
65 Notchback "El Baja Rojo"
65 Squareback "Eggcrate"
87 golf "Winterat"
93 RX7 "Redstur"

-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jeremy
Menzies
Sent: Thursday, November 03, 2011 12:05 AM
To: type3 at vwtype3.org
Subject: [T3] Leak Down Test and Rich Running

Hello All,
I was doing some diagnostic tests on my stock '71 FI Squareback last week
and thought I'd see if anyone had some ideas/input on some of my findings.
I'll try to cut a two month ordeal short.
Story:I drove to San Diego (about 600 miles each way from SF) and on the way
back the car started running poorly and losing power.  It felt as if the
engine was out of balance and the whole car had a heavy vibration
accompanying the power loss.
Data:I finally got some time to take it to do some tinkering with my
mechanic friend (who works on old air-cooled Porsches) and found that the #2
cylinder seemed to be not firing (no response from pulled plug wires or
injectors).  The plug was black all over the electrode and insulator which I
took to be carbon fouling causing it to not spark or spark intermittently
(the running problem is somewhat intermittent, driving OK then coming on and
off).  So, I figure that's part of why I'm losing it but am not yet positive
on why it's fouling in the first place.
Next, I did a compression and leak down test with the following
results.Compression:  #1- 135lbs  #2- 130lbs  #3- 140lbs  #4- 140lbs, which
is all around about 5lbs lower than the last check, done in July.Leak down:
#1~13%,  #2~45%!  #3~12%  #4~26%
After cleaning the plug (which made it run way better) and a little run
around, we hooked it up to the smog machine to find that it's running very
rich.  It's showing at least 4.6-5.3% CO at about 850-875 warm idle rpm.  I
read one D-Jet manual list 2.8-3.1% for '69-'70 and .7% for '72 (with no
listing for '71 and '73).  So, I assume (and my friend was saying) that it
should be around 1-2%.  This added some info to the puzzle and led me to
concoct the following theory.
Theory one is that #2 is leaking enough past the rings that, when combined
with the very rich mixture, is fouling the plug and causing it to drop out.
Along with this, #2 dropping is causing extra wear (26% leak) on #4 since
it's right across from #2.  When #2 drops, #4 has to pick up more of it's
slack than 1 and 3 and is that is taking more of a toll on #4.  This doesn't
explain the rich running and cause of the lost cyl., though.
I'm pretty positive the FI components are all systems go and none are
failing outright.  I did a complete check of the FI components before the
drive, went through the wiring harness checking resistance and cleaning, and
rechecked the two temp sensors the other day, all with positive, in spec.
results.  I've also replaced the voltage regulator and have a steady 13-14v
at the fuse block (if I remember correctly).
I'm now wondering what I can try to lean out the mixture and to see if
anyone has any input on what could cause such high leak down on #2.  I know
that some people (like the previous owner's mechanic) mess with the screw on
the MPS but I don't want to get into that because it doesn't seem like the
right approach.  I've also heard that putting a small washer on the temp
sensor(s) can lean things out but I don't know that that's true.  Does
anyone know of some more adjustments or tests I can do to lean it out?  Any
other theories on why I'm losing 2?  Are #2 and #4 on a slippery slope that
is going to bring the whole lot down sooner than later?
Sorry for the length. I wanted to provide enough information to chew on,
hope it's not too long.  Any and all input is welcome!
Thanks,
Jeremy

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