No Start: Audi 100, 1990, I5 NF engine, non-turbo, non-quattro, CIS-E-111 (California)

[Huw Powell]

> I was under the inpression there is only one ECU in the NG/NF cars. I
> only recall pulling one when I sold the NG out of the 90, and we pulled
> the whole harness with the engine. I ceratinly only saw one in the
> schematics. Unfortunately, I don't have them with me, as I'm in Oklahoma
> right now. When speaking of the ignition control unit, are you refering
> to the small module mounted on a heat sink that has five (I think) wires
> going to it?

Nope.  At least on the NG cars I've seen, there is a fuel computer 
mounted between the fresh air plenum junk and the firewall, and an 
ignition computer mounted in the passenger kick panel below the A pillar.

> There is no harm in hooking up that ground, and running the car that way
> till you can get it repaired properly. Though I still find it hard to
> believe the shop repaired it that way. If it had harmed anything else,
> it would have been on them to repair.

On a 21 year old car getting it running any way that is reasonably 
affordable is the way to go at $80 an hour.  How many early fuel 
injection cars ended up running around with a switch to "hot wire" the 
fuel pump?

How many hours of diagnostics does Marc have invested so far?

I should pull out the schematics and see what that wire they grounded is 
doing...

Oh, and by the way, when checking for continuity with an ohm meter, one 
is testing with very low current - I've seen circuits that tested "OK" 
that couldn't run a light bulb, for instance.

> Send me the part # of your ECU and I'll see if I might have a spare for
> you to use for testing/repair.
> Tony
> On Sun, Aug 28, 2011 at 12:40 PM, Huw Powell <audi at humanspeakers.com
> <mailto:audi at humanspeakers.com>> wrote:
>
>     Thanks for putting all the details in one place!
>
>     I have two comments.
>
>     1. In your list of ground checks you didn't mention the (2?) wires
>     that are grounded to a stud on the intake manifold.
>
>     2. The logic that gets from your symptom and check list to "bad ECU"
>     is flawed, I think, since there are two ECUs as you note, one for
>     fuel (which also runs all that other junk you list), and one for
>     ignition, which only runs, well, the ignition.  Which one is bad?
>       Both?  Just ignition (no spark would shut down the fuel system via
>     the fuel pump relay)?
>
>     Hmmm, wait on that, I may be assuming too much across platforms and
>     model years.  On my NG-engined 88/89 90Qs there are two physically
>     separate ECUs.  Is this not the case with your car?  Did they get
>     around to stuffing them into one box?
>
>     Anyway, you really should try to borrow another ECU to swap in if
>     you can.
>
>     Good luck!
>
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