89 Celebrity, hard start when cold

This car is hard starting at temperatures below -18 C. It will fire but stalls when the starter is released. After several tries it will usually run, if the battery hasn't died by that time. Once running everything is
fine. A friend gave me a GM computer code reader which comes up with Code 12. The book lists that code as: Diagnostic mode; no distributor signal to Electronic Control Module; System PASS. Doesn't seem like much help, does it? :-(
The mechanic at the shop where I take the company vehicle suggests water temperature sensor. I see two, one in the thermostat housing and one directly in the block next to it. I checked with a meter or removed either to test them. Which one is it? Should I go out and buy at $30 or should I be looking for the problem somewhere else?
I did install new plugs and wires, GM (originals) and that improved starting but it still isn't where it should be. I knew the wires etc. weren't in great condition as quite often there was some miss firing taking place at highway speeds.
Any help is greatly appreciated.
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Correction. I 'haven't' removed either temperature sensor yet. One should have a resistance value I expect, for the computer, the other should be a switch for the panel light, right? It's cold outside. :-)

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shopper wrote:

Hi...
Thought 12 sounded familiar, so I went and looked it up.
Mine says that 12 is nothing (no fault); just an indication that it's in diagnostic mode...
Ken
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That's what I surmised too from the chart.
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Car is hard starting at temps below -18 C. It will fire but stalls when the starter is released. After several tries it will usually run, if the battery hasn't died. Once running everything is fine. _____________________________________________________
This can result from a failing ignition switch, where the START contact provides current to the ignition but the RUN contact is intermittent.
Wendy & John. _____________________________________________________
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Hmmm. Interesting. I would NEVER have thought of looking there, but in cold weather anything like that would be aggravated. And that would be another fun job. :-(

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Some follow-up.
I removed both sensors. On is a N/O contact until over heated so this one would be for the panel high temp light. Not part of my problem, however I discovered one terminal was broken off so that high temp light would never have warned danger. This is the one screwed directly into the block.
The other is a resistor type which measured about 32K ohms when cold, (-25 deg C). At room temperature, about 2.7 K ohms.
I'm guessing it's fine and not contributing to my problem. Where to from here?

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sounds to me like your fuel pressure regulator is shot.

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shopper wrote:

Regulator should be on the fuel rail.
Ken
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