cold start weirdness

[SJ]

> From: John Paul Tapp <tappj at videotron.ca>


> Just picking up on this thread - At least 4 of us have the same problem
> - and I've had the problem since 91 when I purchased my 87 Quattro. Only
> happens when the temperature falls below - 15 Celsius. I've tried
> absolutely everything and now just crank away until it starts (great
> starter motor!) Starts great when cold - we've been experiencing a cold
> snap - 32C - drive for anywhere from 15 minutes to 1 hour shut it off,
when I try to re-start it cranks forever.

**** -15C = +5F
-32C = -25F
To re-phrase what you have said.
1. The engine always starts, no matter what the temperature . .at the first
start after a long cold soak(overnight).
2. The engine always starts the second time after a short warmup . .. but
only when temperature is above -15 C.
3. The engine will not start after short warmup . ..  but only when
temperatures are below -15 C.
3a. The engine finally will start after long cranking.

And these are consistent problems and not intermittant?

> Fuel pressure OK if you pull up on the air sensor plate it starts
**** I dont understand this comment. You cannot lift the sensor plate
without removing the rubber air boot.
Are you starting the car with air boot off? Using unregulated air, and
making your own Air/fuel mixture by lifting the air sensor plate? Is that
correct?

I took some readings on the old temperature sensor that I replaced. Its a
two contact sensor. Pin one feeds the fuel injection ECU, and pin 2 feeds
the ignition ECU.
Using a digital thermometer and starting with ice cubes in water in a
saucepan. Put the heat on and heated the water up slowly to a boil.
My wife gave me a hard time when she saw the set up in the kitchen . .
wires, meters, sensors. When I offered to read her nipple to nipple
resistance . . she threw a plate at me.

Temperature readings are in F.
F        Ohms
- 2    13.8K freezer
29      6.0K  garage
30      5.5K  garage
40      4.4k   water in pan
60      3.25k
80      2.3K
100    1.36K
120    880
150    510
180    320
200    225
207    203

Both pins track each other very closely.
Maybe someone will find this useful when tracking down the problem.


> No air leaks
> Lots of spark
> Tried a number of CO settings - no result
> I've also thought of the CSV solution but it usually warms up before I
> get to it.
**** I dont consider jumping the CSV as a solution. Only a method to isolate
the problem . . .and to get me out of a bind when stuck at a supermarket
parking lot.
Since you have a permanent problem . .at least when the temperature is right
. . .it would be easy to take some readings at the CSV and see what is
happening.

SJ