Date: Tue, 26 Nov 2002 17:53:22 -0500
Reply-To: JM/CO <jmerritt2@CAPECOD.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: JM/CO <jmerritt2@CAPECOD.NET>
Subject: Re: Replacement computer
Content-Type: text/plain; charset="iso-8859-1"
There are several possible causes for this symptom, including bad vacuum
lines, or a rupture in the rubber "elbow" in the air inlet system. I would
not condemn the computer without a through testing by someone qualified to
work on these systems, which would probably NOT include your average
mechanic. One quick way to find out would be to substitute a known "good"
one and see what happens. This system is, essentially, a version of the
Bosch "L-Jetronic" system, and, as such, is well documented on the web, as
elsewhere. I picked up most of my knowledge regarding this system from
living with my Jaguar XJ-6 which uses a nearly identical system, although
the engines are not at all similar.
The ECU, or "computer" as some call it, is not a computer in the modern,
digital, sense, but rather an analog device that uses, essentially, 1970's
technology. You could probably build one if you place little value on your
time. The biggest problem would be in obtaining documentation, including a
schematic. To my knowledge, this information is not made available by VW, as
their approach has always been to force the owner into paying out the nose
for a new or "rebuilt" unit. A friend with an 83 Van gave me her old "dead"
ECU a while back, and, being the curious sort, I opened the thing up and
examined it. A diode had shorted ( these sometimes do this for no apparent
reason ) and had burned out a small track on the PC board. A 50 cent part
and about 1/2 hour of my time had the thing functioning just like it should.
I would strongly advise getting one out of a junker that hit the junkyard
for some reason other than a dead engine. I would also strongly advise that
you obtain the service manual for your '86, and go through the checklist for
diagnosing the fuel injection system. These "computers" are a problem which
is bound to get worse in the future, as the supply of good ones is depleted.
Chuck-
'83 Westy
'84 XJ-6
----- Original Message -----
From: "jeremy bornstein" <uke@JEREMY.ORG>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Tuesday, November 26, 2002 9:19 AM
Subject: Replacement computer
> Greetings all!
>
> My mechanic tells me that the computer in my '86 Vanagon is for some
> reason failing to properly control the idle speed, with the result
> that the idle-speed-adjustment-screw needs to be turned way down to
> keep it at around 1000 RPM. Also, replacement computers are
> apparently about $800.
>
> Having some knowledge of embedded computers, but no specific knowledge
> about auto computers, it occurs to me that it might be possible for me
> to build a replacement, at a parts cost considerably less than $800.
> However, I don't yet know enough about the program the thing is
> running, or the complete list of tasks that it performs.
>
> Can anyone point me to more information?
>
> Many thanks!
>
> -jeremy bornstein
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