Hot start

Roa, Greg Greg.Roa at Cinergy.COM
Wed Dec 4 14:55:28 EST 2002

Had a similar problem with my 4kq.  Never got so bad that the car wouldn't start, but always had lousy warm starting abilities.
I finally got it fixed the other day.  My car always smelled slightly of gas after running. A couple of weeks ago, it started REALLY smelling of gas during and after running.  Looked under the hood after shutting the engine off, and saw fuel leaking out of a vacuum line under the fuel distributor.  I figured the distributor itself was leaking, but on closer observation, the fuel pressure regulator (the canister one on the main fuel line) had developed a leak in the diaphragm.  This was allowing gas to flow through it, into the vacuum line which connected to the intake, and then onto the air filter (as well as dripping from the line).

Replaced the regulator with a working used part (thanks Elliot!) and my car starts immediately after a hot run, and on the first turn of the engine in the morning too.  Plus, I've gained some power I didn't know it was missing.

Not familiar enough with the turbos to know if they use a similar setup, but something to keep in mind for 4kq's at least, if a fuel pump check valve doesn't do the trick.

Good Luck!
Greg Roa
Cincinnati, OH
86' 4kcsq
93' 90 CS
83' 944

>From: "Mark Woodland" <markwoodland at>
>To: jeffrey_audi at
>Cc: quattro at
>Subject: Hot start
>Date: Wed, 04 Dec 2002 13:51:30 -0500
>I'm just getting a handle on this with my '87.
>Still not 100% diagnosed, but the workaround (for now) is to mount an
>under-dash switch ($3-$5)that will allow the cold start injector to be
>grounded at will. This will not only prime the car when hot, but will purge
>the air (vapor lock) from the fuel system. My best guess-to-date is that the
>cold start injector is leaking slightly after shutdown, just enough to allow
>a compressable column of air to keep the rest of the injectors from breaking
>over the pressure threshold to start spraying. Its cheap enough to check.
>I'm guessing the Cold Start injector is leaking because I've already
>replaced all of the other injectors.
>The blue/black stripe wire on my '87 TQ is the +12 that comes on when
>cranking/running, and the plain blue wire is the ground that only "grounds"
>when the temp switch sees the head at or around 80 degrees F. If you control
>the ground, you've got it knocked. Just turn it on long enough to
>prime/purge/start, then turn it off, or the car will run waay too rich.
>(Might be helpfull under full boost 8^P  )
>(Unless, of course, you have a vacuum leak, or any one of a handfull of
>maladies that the TQs are heir to.)
>If I had figured this out earlier, it would have saved me numerous no-start
>horrors, calls to AAA, hitch-hikes in stupid-cold weather, and plaintive
>wails from the family...
>Funny you should mention.. I was just getting ready to go outside and
>install the under-dash switch on mine now. I've already tested the concept,
>and was just going out to make it "offical" before the snow flies here in
>frigid PA.
>Give it a shot and let me know how you make out.
>Best of luck!

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