1990 20V no start when cold

[Cody Forbes]

Crap, accidentally hit send! 

I was thinking of additional things to check, but actually  changed my mind. I'll let you get through that message and get back to me.

-Cody
(Sent from my phone, if a word doesn't fit blame Siri)

On Mar 27, 2012, at 6:38 PM, "Mark Rutherford" <mark.rutherford at emerytelcom.net> wrote:

> Looked at the waveforms on both sensors, the RPM sensor has a good sine
> wave, and the TDC has a single spike for each revolution.  I noticed that
> the RPM plug has 5 V DC on it with the key on, while the TDC does not.  Is
> this normal, is it dependent on where the flywheel stops.  I still have no
> fuel injected during the cranking cycle.  It seems like it should have a
> small amount, or am I wrong.  As a further test I inserted a 10K ohm
> resistor in place of the coolant temp sensor.  With this value it should be
> calling for a large amount of cold start enrichment.  Any ideas?
> 
> 
> 
> -----Original Message-----
> From: Cody Forbes [mailto:cody at 5000tq.com] 
> Sent: Sunday, March 25, 2012 6:08 PM
> To: Mark Rutherford
> Cc: <quattro at audifans.com>
> Subject: Re: 1990 20V no start when cold
> 
> Flywheel sensors can be bad and pass tests. Swap both from parts car or
> monitor them with an oscilloscope. Also don't get the plugs backwards, not
> sure if that's possible on your car but on 5000's, 944's and 911's I've
> fixed them many times when somebody confused the RPM and TDC sensor plugs. 
> 
> -Cody
> (Sent from my phone, if a word doesn't fit blame Siri)
> 
> On Mar 25, 2012, at 7:01 PM, "Mark Rutherford"
> <mark.rutherford at emerytelcom.net> wrote:
> 
>> I am looking for ideas on how to fix a no start condition on my 1990 90
> 20V
>> 7A.  
>> 
>> 
>> 
>> Here is a chronological history of work done so far.
>> 
>> 
>> 
>> Initially the car would not start when cold < 40F.  Would start with a
> shot
>> of ether, but would not rev well unless the throttle is eased into.  I
> have
>> replaced and checked everything I can think of( there is a list below of
>> items I have tried).  With the manifold removed and the fuel supply
>> connected I turned over the engine and noticed that no fuel in admitted
>> during starting.  Taking a injector to ground triggers the injector, but
>> they are not triggered from the ECU.  This does not seem right.  Shouldn't
> a
>> small amount of fuel be admitted during cranking?  Any experience, or
>> suggestions out there.
>> 
>> 
>> 
>> Pulled mass air sensor high voltage code.  Replaced code went away problem
>> stayed.
>> 
>> 
>> 
>> Pulled coolant temp sensor code, changed it, original was still in spec,
>> code stayed, problem stayed.
>> 
>> Checked wiring OK
>> 
>> Wired sensor directly into ECU still have code on 2 different ECU's.
>> 
>> 
>> 
>> Found throttle position sensor on bottom of throttle body had fallen off
> and
>> was cooked.  Replaced, still have problem.
>> 
>> 
>> 
>> Replaced the following from a parts car that will start at any temperature
>> and runs fine.
>> 
>> 
>> 
>> Mass air flow, idle stabilizer, throttle body and sensors, distributor,
>> computer and coil.  Still have problem.
>> 
>> 
>> 
>> Checked fuel pressure, 85 PSI, a little high, replaced pressure regulator,
>> holds pressure and meets specs from Bentley.
>> 
>> 
>> 
>> Checked fuel delivery volume, meets Bentley specs.
>> 
>> 
>> 
>> Replaced fuel injectors and rail from parts car, resistor pack, both the
>> original and parts car meet specs for resistance.
>> 
>> 
>> 
>> Check all wiring from plug A on the computer to source, replaced fuel pump
>> relay, RPM and timing sensor, all originals passed tests from Bentley.
>> 
>> 
>> 
>> Placed all parts back on the parts car.  Parts car starts and runs well.
>> 
>> 
>> 
>> Moved parts back to problem child.  
>> 
>> 
>> 
>> Checked pin in the fly wheel , found one about 15 degrees BTDC. 
>> 
>> 
>> 
>> Looked to ensure distributor, cam, and crank are all in sync.  No
> problems..
>> Condition remains.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
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>> 
>> 
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