Date: Sat, 15 Sep 2007 04:26:15 +0300
Reply-To: tinker man <tinkerman007@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: tinker man <tinkerman007@GMAIL.COM>
Subject: Re: It's time to hit that idle Stabilizer on the head!!! (was:
ISCU Bench test)
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Hi John, glad you asked...(I kinda didn't want to nag the list too often...:-)
Lucky I noticed your post, because you changed the subject and I don't
monitor all list traffic. Better to stick to the original subject in
that respect.
On 9/13/07, John Meeks <vanagon@gmail.com> wrote:
> Have you had any response to this request?
Yep, I got many enthusiastic responses, both from techno-dudes as well
as from the general crowd. It indeed seems that fixing these rare
beasts interests many.
The problem is that I haven't gotten even a single
internal-measurement result yet (although several fellow vanagonites
have informed me they are in the works), and but a few external
measurements
I have been working hard (I need that van up and running...:-P) and
have accepted a good idea from one of the list members - to set up an
info page documenting my efforts with the ISCU at VanagonWiki. For
those that haven't been following this thread here are the correct
links (there was a bug in the page names in the first versions):
The parent page describing the various versions of Fuel Injection and
Idle stabilization systems (follow the various links):
http://www.vanagonwiki.net/index.php/Idle_Stabilization_System
In depth description of the ISCU (including a preliminary SCHEMATIC!)
of my ISCU (European 2.1L Digijet system) :
http://www.vanagonwiki.net/index.php/Second_type_of_idle_control_system
I believe this is the first attempt to REALLY "put the screws" on to
the ISCU, including in-depth circuit analysis and debug procedures,
and that's why it's so good to put it up publicly at VanagonWiki, for
the benefit of our community. Of course I'd like to hear about other
resources, such as a good preliminary one I came across (John
kenneke's website):
http://kenneke.com/vwfi/fi.html
I've included a page with my preliminary measurement results:
http://www.vanagonwiki.net/index.php/Measured_results
And I've even added a page for fellow vanagonites to post their
measurement results, but alas, no posts yet...:-)
http://www.vanagonwiki.net/index.php/Community_measured_test_results
This has been quite time consuming and I was expecting (from
preliminary responses) much more info coming from the community,
because as I've mentioned, I have only a defective and it's hard to
get useful measurements from it...:-P
My conclusion? Very few have the knowledge (or time, or tools) to do
the measurements I've described (especially those involving opening up
an ISCU), and although I have the knowledge and time (well, don't have
time but I need that van, so priorities have been flexed here...) I
don't have a working unit to compare with and the fault isn't trivial
to diagnose.
So until I get some useful info or a working unit I'm lowering the
level of my extensive efforts. It's simply not effective shooting in
the dark, although I've learned a lot in the process of debugging the
ISCU and hope to post more info when time permits.
I've even searched the nearby junkyards for both good as well as
defective units, to be able to compare and even do some "serious
operations" without ruining my only unit, without success.
Now rethinking, I also have another idea - I'm sure very few (if any)
list members would be willing to risk their only working ISCU
(installed in their van) to do these measurements - i.e. remove it
from the van, test on the test bench, pull it apart (heaven
forbid!...) for internal measurements...nope, it's too risky if it's
the only one you've got and it's running in your van.
On the other hand, how many on the list have dead ISCU's that they
don't have what to do with, but cannot do any of the measurements?
Maybe they can bring them to nearby technically capable fellow
Vanagonites that can do the measurements (although I think this
resource is scarce too...).
If I could get a few of those defective units over here for
analyzing/playing with, that would surely impove matters, although my
other problem is that I need a European unit ("C" suffix). I'm not
sure the US versions ("B" & D") are compatible. The circuits are
definitely different. Can anyone shed some light on these
compatibility issues?
I've also been taking a shot at analyzing the Digijet 2.1L ECU too. I
found one in the junkyard while looking for an ISCU, but it seems
pretty fried (including the CPU, which heats up considerably and of
course the ECU doesn't work in the van).
> I just pulled all the good bits form an 86 Vanagon on it's way to the crusher and
> could get you those measurements if you still need the data. Why not just a
> DVM across ST1 and ST2?
1. Because a DVM doesn't simulate the real loading of the ICV. The
test light does.
2. Because in case of a failure, those two output pins will be
dead...and this info won't be enough to help diagnose the problem. I
have only one (defective) ISCU, and have been running circles trying
to fix it...(BTW, I think I've verified IT'S NOT the output
transistors (because when I inject a signal ST1 and ST2 indeed become
active), hence the problem is much more complex to analyze, and lies
in the analog computing circuitry.
3. I would be happy to get a scope capture of those (ST1 & ST2) signals though.
> It would be awesome to make these units bulletproof.
Yup, but they're not. I'd be happy enough to be able to fix them
easily when they fail...
OK, rant mode off...:-)
Cheers,
TM
