[s-cars] No Start ABY/AAN engine - Problem Found?
Ben Swann
benswann at verizon.net
Fri Oct 1 21:21:01 PDT 2010
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
:
[ Date: Mon, 27 Sep 2010 00:34:26 -0400
From: "Ben Swann" <benswann at verizon.net>
Subject: Investigation further[ Fusebox internals - map/diagram]
To: <audi at humanspeakers.com>, "'John Cody Forbes'" <cody at 5000tq.com>
Cc: quattro at audifans.com, '200q20V mailing list' <200q20v at audifans.com>
Message-ID: 71CB33CEFB2B415885FA1BD1E285E993 at swansong
OK - I have been poring over wiring and connectivity to figure out why the engine does
not start and run.
Recap for those who are interested:
ABY "S2" engine installed with ABY wiring harness. All connections for the harness are
to the fusebox per factory. Ancilleries like instrument cluster - Tach, etc. are left
unconnected.
On Crank, the fuel pump does not run. Checking obvious suspects starting with Hall
Voltage and operation - that is good and switching.
Diagnostics attempted both by wiring for VAG-COM and simple LED test hookup do not work.
The LED lights when switch on with ECU but not signaling. I did verify all wiring is
connected properly - OBD power +/-, OBD K/L, OBD blink.
I don't want to just plug another ECU in since if wiring is incorrect and full voltage
on wrong pin could concievably be damaging the ECU. So I checked all harness pins at
connector w/o ECU:
First testing all 55 pins w/r ground no battery negative connected: Pins 7, 10, 14, 19,
24, 26, 52 showed some connection to ground.
With battery connected: checked for voltages reveal: 12V on harness pin 18 - that is the
unswitched power supply so OK. What did not make sense is that I saw 3V on pins 3 and
27. Both these lead back to the Fuel Pump Relay terminal
That corresponds to ignition on - I think, terminal 86 on the relay. Some diagrams show
as 46.
Anyway, I'm wondering where that 3 V is coming from. It is fairly consistant -
something in the car like a voltage regulator or the current that goes through a relay?
Is this normal? That is if the key is off and voltage checked on the relay terminal 86
[no relay inserted] that voltage is around 3? Would this cause a current drain or just
voltage present?
Also, I continued to test through all 55 pins again - when ignition switched on, I got
12 V where there was 3V ( pins 3 and 270 and also on pins
18. 8.75V on terminal 50 (vehicle speed signal - from tach)?
Weirdness.
Ben ]
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