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

n-engelbert at terrans.net n-engelbert at terrans.net
Tue Jul 26 16:29:02 EDT 2005

It's possible that I'm vaporlocking as well, but this is even almost
immediately after shutting off the car.  The fuel pump was replaced last
year with a Pierburg unit.  This pump has an internal check valve.  The
car restarted great for a month or so after I replaced the failed bosch
pump (in the parking lot, at an autox), and then restarting got bad again.
 I'll pop the fuel pressure gauge on and see if pressure is bleeding off
again.  Or, I could jumper the fuel pump relay closed with the car off,
let it sit for a few minutes artificially holding pressure, and see if it
restarts more easily.

Anyone have an inline check valve that they're using?  I'm thinking
something like the valve at the bottom of page 357 of the online McMaster
Carr catalog.

But, the tach will not move at all when cranking hot.  Then, all of a
sudden, the tach will move while cranking, and the car will start.  Maybe
it's all in my head.

Sorry for the long reply, there will probably be more while I try to track
this down.

Nathan Engelbert
83 UrQ DA900453
89 90q
91 200q20v donor
91 200q20v avant

> Guys, please correct me if I'm wrong, but I believe there are reference
> marks on the flywheel that determine when and where to spark.  If you are
> able to visually check for spark, and there is one, it is possible you've
> got fuel vapor lock at the injectors.  I also get this from time to
> time...
> HTH,
> Jim
> -----Original Message-----
> From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On Behalf
> Of n-engelbert at terrans.net
> Sent: Tuesday, July 26, 2005 4:06 PM
> To: urq at audifans.com
> Subject: [urq] No hot start (speed or reference sensor?)
> 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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