'89 200 Won't Start

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Well, actually it will start, but only on about 1% of the attempts I make. A friend who's much, much smarter about all things mechanical than I has
been helping me troubleshoot this problem for the better part of a week, and we're mostly stumped.
The problem is a lack of spark. On those rare occasions when we actually get spark, the car fires right up. And since the spark is plenty strong when it's there, we've been looking for problem either with the ECU itself or with one of its inputs. (Yes, we've checked all the connections in the ignition system, checked the distributor rotor and cap, and so on.)
Near as we can tell, the problem is the signal from the crank reference sensor (located right next to the RPM sensor on the driver's side of the block) being too weak. We've tried replacing the sensor, but the signal is still weaker than my brainy friend thinks it should be. So we rotated the flywheel until the pin that this sensor is supposed to react to was right under where the sensor goes, put some putty on the end of the sensor, and stuck it in its hole to check the clearance. We actually got a bit larger gap than the .040 that the Bentley manual specifies, but close enough that it shouldn't be a problem -- say, about .060.
But what we noticed that seemed a bit odd was this: The indentation from the pin in the putty only went about halfway across the "business" end of the sensor. It would seem to me that in order to generate a decent signal, this pin should extend all the way across the sensor's surface as it whizzes by. There really isn't any wiggle room in which to adjust the sensor so as to move it closer to the flywheel and therefore get a better reaction from this pin, so either our observation (about the pin only coming halfway across the bottom of the sensor) is normal, or there's something wrong with the pin. We didn't see anything in the Bentley manual about this particular detail (doesn't mean it's not in there somewhere), so I'm hoping that somebody here can help out. FWIW, the starter was replaced (by a mechanic) just prior to this problem cropping up, so it's not completely impossible that this pin was somehow damaged in the process.
Can any of the gearheads here confirm whether our observed alignment of the pin with the crank reference sensor is normal or not, so we can either pursue fixing it or move on to something else? (And we're pretty much completely out of "something else's" at this point.) And does anybody have any other ideas as to what might be the problem?
Many thanks in advance!!
- Greg
--
1976 Cadillac Fleetwood 9-passenger sedan
(for sale: http://www.dataspire.com/caddy )
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There have been several experiences like this posted at the AudiWorld forum for type 44s lately. You may want to check there and search the previous threads or ask the question. Lot of talent there.
http://forums.audiworld.com/v8 /

The spec that you are observing has, again, been discussed at AudiWorld. I do not know it off hand but it should be easy to find references to it at the forum.

Hall effect module in distributor have an intermittent?
I thing that your suspicion about ECU inputs being the cause is most likely the issue.
Tony '91 100Q 5spd
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Greg, Have you tried reading the fault codes in the ECU? see www.sjmautotechnik.com about fault code retrieval - what do they say? It's possible that the pin got bent if the old starter self-destructed..? You can remove the new starter (it's a pain, but at least the nuts aren't siezed) and look at the pin to see if it's been hit/bent/???. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Before you get too far with ignition, you can check if the fuel pump (pressure) is ok. I had intermittent stalling problems and ultimately had the pump replaced. In some cases you can try to force drive the pump prior to cranking (to build pressure). It is done by unplugging the fuel pump relay and jumpering its wide slots. By doing so the pump is constantly running (for the duration of the experiment). Let it pump for a minute and then crank. It it starts - the problem is low fuel pressure. Plamen, Toronto

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