Weird MC engine problem

[Jim Green]

Good to hear from you Phil!

--- Phil Payne <quattro at isham-research.com> wrote:
> Before I start - this car is a dog.
>
> It's an Audi 200TQ (5000) with an MC engine run by a
> MAC14.  It was off the road for an
> unspecified period, believed to be long, and then
> had some kind of electrical event.
> Basically every component on the auxiliary relay
> panel with a transistor in it was fried.
>
> The ignition switch is also extremely suspect and
> the tachometer and trip computer are dead.
>
> Anyway - I've gutted and rebuilt the electrics.  The
> diagnostics run and the ECU stores no
> codes.  The car will start and idle from cold - duty
> cycle is 50%ish at idle, ISV current 440
> milliamps.
>
> If you try and put any appreciable load on the car,
> it dies instantly and won't restart.  At
> this time, an attached code-pulling LED illuminates
> permanently.  If you cycle the ignition,
> it comes back on with ECU power.
>
> I've swapped the ECU and coil pack for known good
> ones and tested the swapped ones in another
> car.  Also the control pressure regulator.  The fuel
> pump has been swapped - pressures and
> flows are within specification.

You say you rebuilt the electronics, I know I had one
of my main power relay's go out once, caused all kinds
of problems.  The only way I figured it out was it was
hotter than hell when I put my hand on it.  It sounds
like something is shorting out.  Could be that
ignition switch?  I don't know haw that would be load
dependant though.  Damn, this is a tough one.

Later,

=====
Jim Green
'89 90tq 034EFI, Haltech IG5
http://www.geocities.com/jeg1976/car_home.html

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