[urq] No hot start (speed or reference sensor?)

[Buchholz, Steven]

... everybody ... have you read the IST Documents?  If you haven't had
the opportunity, I recommend that you make time to read them over ...
they are readily available on Martin Pajak's site (oops!  Martin, I'll
get you those scans of the '83 wiring diagram today!)  The IST Documents
provide quite detailed information about how many parts of the urq
operate ... 

The WX engine has three sensors that provide timing reference
information.  Since the engine has an odd number of cylinders, all 3
need to be fully operational for the engine to start or run.  There are
two sensors on the flywheel, one that looks at the teeth, and one that
looks for a reference pin.  The other sensor is that Hall Sender in the
distributor, which the F/TCU uses to tell whether the reference pin is
registering the even or the odd cycle of the engine.  In actuality, the
Hall sender makes every other reference mark invisible to the F/TCU.  

It could very well be the case that one of the flywheel sensors is flaky
... but it could be the Hall Sender too.  The IST docs have
troubleshooting info ... 

Steve B
San Jose, CA (USA)
> 
> Recently on my 83 UrQ DA900453, the car has started fine when cold,
but
> will not restart when hot.  When cold, the tach bounces as I'm
cranking,
> presumably at the speed the engine is cranking, but when hot, the tach
> does not bounce, I don't believe I have spark, and consequently, the
> engine won't start.  As of last fall, the fusebox (under dash) and
> ignition switch were new.  Spring 2003 the transistorized ignition
switch
> in the glovebox was new.  Once I can get the engine to start, though,
it
> runs as if nothing is wrong, leading to the belief that I may have a
flaky
> sensor.
> 
> The question is:
> 
> Is there a sensor that the ECU only uses when cranking to determine
TDC,
> and therefore, when to spark?  This sensor would drop out of operation
> once the engine is started.  I'm going to stop by radio shaft to pick
up
> some freeze spray to bring the offending sensor back to cold on hot
> restart until I swap in my 3b sometime after the CT UPG.  I skimmed
the
> IST documents and didn't see anything on my first time through.
> 
> Does anyone else's car's tach bounce when cranking?  Should it move
when
> cranking?  My 90 and 200q20v's tachs don't bounce that I remember.
> 
> The car's been in storage for a while, but this happened last fall as
well
> before I parked it for the winter.  I can check ECU voltage and step
> through the IST instructions if I can't find the problem quickly
without
> removing the ECU (easy, I know).
> 
> Man, I need a scope,
> 
> Nathan Engelbert
> 83 UrQ DA900453
> 89 90q
> 91 200q20v donor
> 91 200q20v avant
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