[tech] Help diagnosing an 8V?

[m-carlson@comcast.net (Michael Carlson)]

Sorry for the late reply; it's been a busy day...

Well, I performed the OXS control unit tests per the Bentley today.
According to those tests, everything checks out.  (I feel like a certified
Scirocco owner now that I've actually made and used my very on fuel pump
relay switch.)  I also performed the oxygen sensor test, and it checked out,
too.

Beyond the tests, I watched the frequency valve duty cycle as the engine
warmed up.  Just out of curiosity, please verify that the following behavior
is correct (or at least reasonable):

1)  While the engine was cold, the duty cycle was solid at 50% (even when
the engine ran rough and stumbled).
2)  Once the engine warmed up a bit, the duty cycle fluctuated between 40%
and 58%.
3)  A little later, the duty cycle fluctuated between 45% and 56%.

> Have you done the test in Bentley for the Thermo-time switch?  Might want
> to check that too....I doubt it is the problem, but might be worth
> checking.

I believe my thermo-time switch is broken.  I didn't get any resistance from
it when the engine was cold, which means it's probably never turning on the
cold start valve.  I didn't have enough time to pull out the cold start
valve and verify this, but I trust my meter.  That would explain the hard
starting when cold, but I doubt that's causing my rough-running issue.

> Oh man...now you gotta pull the injectors and check their spray
> pattern...maybe number 2 is just dumping fuel....

I suspect this is my next step.  Argh.  Now I need to get an injector puller
and some new O-ring seals (been meaning to replace those for awhile now)...

> No problem, I mean, I am just throwing ideas out....looks like my first
> hunch may have been wrong....

There's no shame in that.  At least you gave me a direction to start
marching in.  There's just as much value in verifying what the problem
*isn't* as figuring out what the problem *is*.  (Can you tell I'm a software
engineer?)

> but, when your all done here, you certainly
> will know every good and bad part of your injection!

True enough!  There's nothing wrong with that, as far as I'm concerned.  :)

Oh yeah, one more thing.  While I was scrutinizing stuff today, I discovered
that the rubber sheath on the line between the fuel filter and the fuel
distributor had some visible cracks in it.  Could that be letting unwanted
air in the system, or is that rubber sheath just a protective layer for the
fuel line?  Either way, I plan to replace it--should I go ahead and replace
the fuel filter while I'm at it?

Mike Carlson
'84 Scirocco Wolfsburg Edition (slightly ill)
'95 GTI VR6 (daily driver again)
http://www.divergent.org/mikes.vws/