[s-cars] No Start ABY/AAN engine - Problem Found?

[Ben Swann]

Scott, All,
 
I am considering doing this - anything beats pulling the trans out again.  So I have a
few questions and other possible solutions to run by you.
 
First, on the reference pin for the 3B flywheel - looks like  I need to match the exact
point to get the pin in order for timing to be dead on within a degree of rotation or so
I understand that this is a critical location with no tolerance for error - correct?  
 
At first measure using spare 3B flywheel aligned on top of original AAN flywheel as
reference, the new pin would need to be located in the same spot as the pin that locates
the pressure plate.  I presume this is hardened steel and I'd be drilling through the
locating pin and through the hole the pressure plate already has drilled.  Where exactly
did you locate the pin when you did yours?   Any clues that I can see from behind the
flywheel?  Did you in fact end up drilling through the orignal locating pin?  
 
Can I use a good grade 8mm stud, drill and tap and screw the bolt/stud in, or is a pin
that much better?  I just feel a threaded stud with red locktit would be more secure
than a roll pin.  When you say 11mm - is that the diameter of the pin or you mean the
amount of pin protruding from the flywheel surface?
 
Any more tips on replacing the pin through the starter hole would be helpful.  It seems
like a difficult job, especially regarding the need to be exact, but surely easier than
removing the transmission.
 
On what I did since last email:
I confirmed the provisional epoxied location works as far as generating a good signal -
even better than the original location.  Even though this was a provisional test, there
is no way the metal epoxy I used and the way it was applied was going to come out on it
own - heat cycling or not!  Anyway, the signal was better than the stock location.  This
I found after redoing the job and making a spacer.  Got very good signal, but now it is
before the hall window by a few degrees - enough to be out of window after instead of
before.  So now fuel pump trigger once, exactly at the pin location, but shuts off
abruptly and still no start.   The original reading on the sensor was also picking up
"noise" from the pressure plate shape - it appears the original pin location is not
ideal.  If you look at the location and see how the pressure plate is mounted, this
becomes evident, and I was picking up  the various metal shape of the rotating pressure
plate instead of just a pin (or two).  
 
So..I am considering another alternative -  a backup plan to the flywheel drilling in
situ.  This is to simply drill a hole through the trans bell-housing at the precise spot
where the sensor should go probably a few degrees counter clockwise on the trans
bellhousing from where it is now.  Seems I may be able to drill proper size hole and tap
a fitting in that can retain the sensor to the proper depth.  This seems like it should
work since the way the pin is located now there is a very good signal - the sensor is
about a mm from the pin when it is closest so the sensor almost brushes the pin.  I
could bring the hole in a bit closer to the flywheel too, since where it is now the pin
protrudes about halfway under the sensor.  I scoped the signal and found it to be more
precise than when it was in the stock location, but probably if it saw more pin then the
signal would be stronger.  I just need to determine where exactly to drill and therein
lies the difficulty.  Good Idea?  Problem?
 
Some day I may pull the trans out and install an aluminum flywheel and beefier clutch
setup, if needed.  Right now I'm pretty sure the disk and PP are adequate for moderate
power levels around 400 HP and would be a big step backward to pull the trans again.  It
would be nice to get this car running and on the road - the project has been in works
now for over 4 years!
 
Ben 

  _____  

From: qshipq at aol.com [mailto:qshipq at aol.com] 
Sent: Saturday, October 02, 2010 11:14 AM
To: cody at 5000tq.com; benswann at verizon.net
Cc: chris.miller at bqconsultants.com; s-car-list at audifans.com; quattro at audifans.com
Subject: Re: [s-cars] No Start ABY/AAN engine - Problem Found?


Cody et. al
The first line caught my attention...  You absolutely *can* do timing reference pin in
situ, btdt on various bodied cars probably 10 times in the last 20 years.  Never lost
one either.  Drill bits and red locktite, btkabitzedthat in the condo garage at
Steamboat

Agree on 'no' to the cam timing as timing pin reference, that's got more slop than the
flywheel pin placement, and unlike the flywheel pin, it will vary on temp, tension and
load, and 2 revolutions doubles the slop by definition

The best wave form from the crank pin comes at 10-11mm 'pin' width IME/Measures.  Easy
math:  The further you stray from that dimension, the closer the sensor has to be to the
pin.  I'm pretty convinced that's the main reason why audi switched from the pressed pin
to the cast nub (and  IIRC the nubs I measured on AAN FW are ~11mm - hmmmm).  I've
replaced dozens of 'bad' timing reference sensors on MC motors, can't remember doing one
on an AAN.

epoxy (I call proxy) mounting....  heat cycles and vibration, epoxy will crack, Murphy's
law says that will not be in your driveway.

Ben I'm not sure I'm clear on what combo you are using, but I read your end conclusion
to be you need to relocate a timing pin.  My suggestion:  Pull the starter (I drop the
subframe too, it's easier) and get an expensive drill bit (at least 1), that fw is made
of kryptonite.  Measure the critical diminsion from FW teeth to nub.  Go slow, or you
will snap the bit off.  Then use loctite red, and insert the next size drill bit shank
side first...  Tap with a hammer to seat, cut the bit to length with a dremel (the
longer the better the signal wave strength -  as long as it makes a revolution without
hitting the block).  Install starter, subframe up.

HTH and my .02

Scott J
FW pin professor emeritus



 
-----Original Message-----
From: John Cody Forbes <cody at 5000tq.com>
To: Ben Swann <benswann at verizon.net>
Cc: Ben Swann <benswann at verizon.net>; <chris.miller at bqconsultants.com>
<chris.miller at bqconsultants.com>; <s-car-list at audifans.com> <s-car-list at audifans.com>;
<quattro at audifans.com> <quattro at audifans.com>
Sent: Sat, Oct 2, 2010 7:46 am
Subject: Re: [s-cars] No Start ABY/AAN engine - Problem Found?


First off, you can not accurately place the pin in situ. The hole must be 

drilled using a milling machine. It is critical. 



Second, you do not want the pins on the cam. The timing belt has slop and the 

valve springs cause the cam to bounce back and forth in this slop. This will 

cause an ignition timing variance. Because it's on the cam that variance will be 

doubled. You do not want your ignition timing bouncing around +\- 10 degrees 

;-).



I've got more input, but I have to get back on the road. I'll send another 

message at lunch time.



-Cody (mobile)



On Oct 2, 2010, at 12:21 AM, "Ben Swann" <benswann at verizon.net> wrote:



> Well I believe I have found the problem and it is not one of those where 

finding the problem is most of the battle.

>  

> I have suspected something up with signal  synchronization between the Hall 

and Flywheel Crank Reference and Crank Position  sensors, but everything seemed 

to be checking out electrically.   I borrowed a Vantage Probe in order to check 

the waveform on the sensors.  The hall is putting out a nice square wave right 

where it should.  What is difficult to see is the pulse on the flywheel sensors 

- very slight, although the ref sensor does trigger the fuel pump relay.  Yet 

the car won't start and fuel pump relay only trips on briefly as the engine 

turns over.

>  

> I manually probed for the flywheel pin - there is a convenient hole in the 

trans that shows the  first pin to coincide about dead middle of hall window.  

At first I though - so this is not the problem, but then realized that the ref. 

sensor is mounted lower on the bellhousing - almost by 60 deg.   Bad thoughts 

that I might be missing a pin - no they were there.  But did not make sense that 

the first pin was basically going to be sensed about 60 degrees too late - after 

the hall window closes.  Basically you can think of the hall sensor as opening 

up a gate for the other signals to pass through.

>  

> So, here is the information that I did not give earlier because I did not 

think it relevant - I used the flywheel from a 3B engine from 200 quattro 20V.  

Why?  Because earlier research indicated it was the correct thing to do and the 

dual mass spring loaded AAN flywheel parts are more  expensive and have possible 

durability issues.  I was for some reason under the impression that they were 

basically interchangeable.  Well they are, except for one thing - the flywheel 

pins are located differently.  In fact, the AAN flywheel does not really use 

pins, but has metal protrusions.  So, at first inspection things looked OK and I 

installed the 3B setup.  Now that I am looking and on closer inspection, the AAN 

"tabs" happen at just after TDC and about 60 degress later for the second tab.  

Whereas the 3B pin #1 happens about 60 deg. after TDC and #2 60 deg. after that.

>  

> So, the logic of the AAN ECU must have been recoded for different pin location 

- all other things being similar on the engine crank, bellhousing, etc.  GOTCHA!

>  

> Now, I'm trying to figure out how I can make this work without pulling the 

transmission out.  I'm exploring some ideas and appreciate if anyone has a good 

way out of this predicament - maybe someone has dealt with this very issue and 

has a good solution that is easily implemented.

>  

> So far i've considered:

>  

> 1. pull trans and install AAN flywheel setup.  This is probably the most sure 

fix, but I already pulled the trans. out after installing due to an issue, and 

now it is even more difficult with everything completely hooked up - axles, 

wiring, exhaust.  I really don't want to do this again - I'm so close!

>  

> 2. install a pin in the flywheel in situ somehow.  I may be able to access 

through the starter hole, drill and insert pin  through.  Investigation reveals 

that I would not be able to do this without drilling through existing hardened 

pressure plate retention peg - located ironically just where the pin would have 

gone.  Still this is an option if I can locate the pin accurately.  I would 

probably need to yank the second pin that would now be pin #3 - I presume it 

would throw things off on startup.

>  

> 3.  a. Relocate the sensor.  This option I toyed with a little already.  There 

is that hole in the transmission I mentioned - it is right where one would 

expect the pin should be at TDC.   This is a feature in the 01E transmission 

installed.  I epoxied a spare ref. sender in the hole using a spare bracket.   

However, I was not able to get a good read on the pin - maybe I just need to 

seat is in a bit farther.  That epoxy is holding better than I thought, so will 

need to be removed by force. 

>  

> I toyed with a few spare sensors using the scope.  The flying steel pin/tab 

needs to almost come directly in contact with the sensor.  If I brushed the 

sensor with a large steel screwdriver, I could get a spike, but waving the 

screwdriver about 1/16" away gets nothing.  A gap the size of a business card 

works OK.  This is a very close gap, and the sensor would be reading near the 

end of the pin.  I did verify that I could get a good read near the edge of a 

pin using a spare flywheel - showed good on scope and also trigger the fuel 

pump.

>  

> 3b.  What if I mount a pin (or two) on the cam sprocket and hang a sensor off 

the cover plate with a bracket?  Can I get away with 1 Pin?  Is the second pin 

required?  Also, since the cam only revolves once every crank rev. I might need 

another set of pins 180 deg. out.

>  

> Ideas.  Has anyone installed the 3B flywheel on AAN/ABY or other  - I was sure 

I read this, but apparently did not get the full picture.  I'll probably work 

with 3.a. tommorrow some more, but perhaps there is a better idea!  It would be 

so nice if there was a jumper inside the ECU that deals with this!

>  

> Ben

> 

>  MAJOR SNIPPAGE..