Yeah I guess some have only one sensor. A shop manual or guys at Napa could confirm.
There are 5 coolant temp sensors that screw into coolant jacket on my early 90’s Corolla
- Used by computer to calculate coolant-temp related engine-operating parameters
- Used to display coolant temp on dash gauge
- Used to control operation of engine fan
- Used to inject extra gas on cold starts
- There’s one more, but forget what it is used for … lol … edit: just remembered, number 5 is for purge valve control.
As you might expect, this creates much confusion at parts store when asking for a “coolant temp sensor”.
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I stand corrected. I did a little looking in my old textbook and a few ECU tuning sites. Seems that 9 or 10:1 is a good starting value growing to 14.7 (14.1 for E85) once warm and closed loop. I’d guess that extra fuel helps heat up the cats, too.
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I expect one of the issues for cold-start mixture calculations is the fuel doesn’t vaporize as readily when cold. More is needed b/c some of the gasoline injected doesn’t combust.
In the old days or on snow blowers you would choke a cold engine. Thi reduces the air flow or in effect richens the fuel mixture. Choke a hot engine and it floods.
My lawnmower has no choke, but a little rubber bulb can be pushed to inject some extra gasoline from the carb fuel bowl into the air intake path. That bulb ripped open on mine, so now have to use a bicycle pump to get it running in cold temps … lol …
It has a choke but it is automatic so no lever to pull. That’s the way my pressure washer is. It can be problematic though on a hot restart. Push the prime bulb a couple times, choke it, bring it up to tdc And it starts.