'87 5KCSTQ reluctant to start cold

[John Larson]

On 1/10/2015 8:11 AM, ekellock at gmail.com wrote:
> I had the exact same thing happen with the valve at the fuel pump on 
> my 89 200q. I went in expecting to replace it and found that it was 
> just loose. Tightened it up and all was well.
>
> Ed
>
> *From:* cobram at juno.com <mailto:cobram at juno.com>
> *Sent:* ‎Thursday‎, ‎January‎ ‎8‎, ‎2015 ‎11‎:‎09‎ ‎AM
> *To:* viejoloco at comcast.net <mailto:viejoloco at comcast.net>
> *Cc:* quattro at audifans.com <mailto:quattro at audifans.com>
>
> I had a similar thing happen on the 200TQA many moons ago.  After much
> diagnosis and shotgunning, it turned out to be the fuel return valve at
> the fuel pump was a bit loose or defective and would lose pressure when
> the car sat.
>
>
> I found a copy of my old post about this:
>
> "When the return valve was loose, it took a whole lot more than 5 seconds
> to start, and wouldn't start at all depending on whether the engine was
> up to operating temperature or not.  That one was a btch to figure out,
> since the valve was failing intermittently, and would test fine.
> Check valve is something everyone should keep as a spare when you change
> fuel pumps (usually get a new one with fuel pump), I think it was around
> $35 as a separate item, and if you have one on hand, it's probably faster
> to just change for a known good one than to test it."
>
> BCNU,
> Experience is the name everyone gives to their mistakes
>
> John Larson <viejoloco at comcast.net> writes:
>
> >Cold meaning "sitting until the engine is at ambient
> > temperature".  To answer another post, the fuel pump runs when the
> > car
> > is in a cranking situation.  Fuel pressures appear to be normal.
> > I'll
> > confirm that this morning.  Temps here are currently about 60
> > degrees.
>
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Good idea, but my system holds pressure.  Update;  The test for the temp 
switch is to compare it with a known good one.  They're cheap, and 
Autohausaz had one for cheqap, so I'm awaiting its arrival.

John