Date:         Tue, 13 Apr 2010 15:44:02 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Do U carry spare ECU?
Comments: To: pdooley <psdooley@verizon.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 03:14 PM 4/13/2010, pdooley wrote:
>Could we assume the injector drivers are not getting enough current to open
>the injector solenoids due to faulty solder joints limiting current flow?
>Noid light only shows the signal, not the strength, as Mark pointed out.

Another reason for driver-transistor failure is connecting or
disconnecting the load while the ECU is powered.  They warn you about
this in the book and they're not fooling; and the fact that it didn't
fail right then doesn't mean you got away with it.  It can easily
generate voltage spikes that will try to punch through the thin
insulating layer inside the transistors, and the damage can
accumulate until the Xistor fails in operation.  However I think that
would usually cause the transistor to fail short in some way (when
they melt they tend to fail open).  I'm pretty sure these transistors
are field-effect transistors, but they're operated in what would be
called open-collector mode with a junction transistor.  That means
that the power to the load is supplied externally, and the FETs
switch the load on by opening a low-resistance path to ground; so if
you'd punctured one the 'noid light should stay on continuously and
the injectors would spray as long as there was pressure in the system
and ECU powered.

Yours,
D