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

[Marc Boucher]

Hi Huw and Tony, the schematics for the ECU are located on page 4 of this link:

http://audi.service-bg.com/Articles/usermanuals/Audi-80_90_100/audi100_90_wiring.pdf

The ECU of the NF engine is documented here:
http://www.sjmautotechnik.com/trouble_shooting/100ecuf.html

It consists of a fuel injection unit labeled "Jetronic" at the passenger's footwall.  It has as 35 pin connector.
Then there is the Ignition Control Unit, which is labeled "Bosch" and has a 25 pin connector.

I'm trying to be careful in terminology...
ECU:Engine Control Unit, consisting of both units, the ICU (Ignition Control Unit) and the Fuel Injection Control Unit.  Huw's point was well taken however, if I went to swap one out, which one would I replace?

The two ground wires on the intake manifold were checked.  The only ground wire I haven't been able to find is the one that Tony mentioned in a prior email, reading from the Bentley manual, as going to the base of the right side A pillar.  I'm wondering if this wasn't for a different model other than the NF.  Note that even although I can't physically find the endpoint of that ground, I can still confirm that all the PINS mentioned and labeled as ground in the attached PDF, are in fact ground.

MC

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From: "Huw Powell" <audi at humanspeakers.com>
Sent: Sunday, August 28, 2011 6:22 PM
To: "Tony Hoffman" <auditony at gmail.com>
Cc: "Marc Boucher" <mboucher70 at hotmail.com>; <quattro at audifans.com>
Subject: Re: No Start: Audi 100, 1990, I5 NF engine, non-turbo, non-quattro, CIS-E-111 (California)

> 
>> 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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