cold start? warm start?

[Brian Devlin]

My 86 5ktq (MC engine) has been reluctant to start, especially with a
cold engine on warmer days. Here's what I know so far:

Observations:
<50F, cold engine, starts on second try.
at 60F, cold engine, very difficult to start.
>60F, cold engine, ????.
Warm engine, starts with a couple seconds of cranking.

Tests:
Cold start injector does not fire at 60F.
12V to the colds start injector is very helpful at 60F.
Air temp sensor test OK (404 Ohms at ~55F).
Both coolant temp senders seem OK, but ambient temp was a bit low
(>1000 Ohms). They gave the same reading on the warm engine.

Questions:
Why are there two senders providing the same info?
Is the two wire thermoswitch for the idle stabilizer?
What about the big scary temp sender under the coolant pipe?
Is there a thermo-time-switch on this car?
If I attach a VW 1367 "according to manufacturer's instructions" what
is the duty cycle that I would measure?
Is the Bentley manual really that much better than the Haynes?

-Brian

Yes, I will soon try to read the codes.