Cold Starts / Really Cold

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RichLo

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Something to remember about cold temps is that wind chill means nothing for vehicles. That is just a metric used to measure how fast a living creature will have heat removed from the body.

-10* ambient with a -40 wind chill means that your face or exposed skin will get frostbite in the same amount of time as if it was -40 with no wind.

A vehicle sitting in -10* weather overnight cant get any colder than -10 no matter how fast the wind is blowing.
 

Schurkey

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Something to remember about cold temps is that wind chill means nothing for vehicles. That is just a metric used to measure how fast a living creature will have heat removed from the body.

-10* ambient with a -40 wind chill means that your face or exposed skin will get frostbite in the same amount of time as if it was -40 with no wind.

A vehicle sitting in -10* weather overnight cant get any colder than -10 no matter how fast the wind is blowing.
Wind chill doesn't quite mean "nothing" for vehicles.

Just like skin, they cool FASTER, but not COLDER than the "real" temperature.

But since they do cool faster, you can't count on "residual heat" when starting a vehicle parked outside in the wind. A 600-pound lump of iron and aluminum that started out at ~190 degrees, and which might retain some heat in still weather for several hours may be totally chilled in that time when it's windy.

But the main thing with wind-chill is that the National Weather Guessing Service can get everyone scared by yap-yap-yapping about extreme weather. "Sixty Below" (wind chill) sounds WAY worse than "-20F and strong wind", which gets folks riled-up and watching The Weather Channel's sensationalist crap, and whining 'n' crying about travel. Around here, anyway, the NWGS could be every bit as wrong about the weather with half the funding and one third the staff. They can't accurately predict afternoon weather from late morning.

But they know exactly how warm the Earth is going to be in fifty or seventy years.
 
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RichLo

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Very true about cooling down faster. I was just getting at if a car sits over night there's a big difference between -40 and -10 with a -40 wind chill.

And forecasts are wrong 100% of the time... whether is weather, business earnings, stock prices, etc. They are predicting the future. I like the forecasts that give the best and worse case scenarios and show those models into where that info is coming from, that gives me a good range of expectations and not just this is what it'll be. How far off is what gives them credibility or not. Anybody can look out the window and say it'll be cold, windy with a possibility of snow. But the good forecasts can get within a couple degrees, a few MPH wind gusts, and show where the snow will be and how much will accumulate in those areas
 

thinger2

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-20F (real temperature, not "wind chill") is not cold enough for a vehicle in good condition, winter-weight oil, and winter-blended fuel to fail to start.

Carburetor or fuel injection--doesn't matter. (Assumes the carb has a properly-functioning choke.)

I don't know what was accomplished with the five seconds for the vehicle to "think". I'm more likely to believe it was coincidence; or an additional fuel-priming cycle.
He also said he boosted it several times before it started.
Did it slow crank the first time?
Weak or frozen battery. Bad connections etc.
Did you crank it over and over again and it got slower and slower?
Hot starter.
Dont keep cranking on the starter when it turns slow thinking that it is the battery though it does drain the battery pretty quick.
The starter is a high reduction motor and they get really hot really fast.
That is why you can crank an engine and it gets weaker and weaker untill it wont crank at all.
Then if you wait a few minutes it will kinda crank again.
That is not the battery rebounding though it kinda does.
That is the starter cooling off enough that resistance in the windings drops.
Probably coincidental, probably accumilated heat from cranking.
But cold wire energizing is a really big part of aviation starts.
You often key on a circuit to warm it and to test it.
When you power a wire its resistance changes with heat.
And the feedback from that sensor changes.
These trucks are obviously not built to aviation standards.
But they are from that same generation of systems development but have a much looser and cheaper "out of bounds" set of parameters.
Plus, if you have a sketchy connection someplace.
Key on and off and a jump box might just warm that up enough to make it work again.
It has nothing to do with letting it "think about it"
Thats just a term he used to describe what his results were after the whole episode.
Im cold as hell reading this and its 18 degrees above zero here.
 

gwolf

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It could be coincidental but possibly just some extra time for fuel pressure, but the fuel is good. I just know what happened. No trouble light/code thrown either. This also works on some bike ecm's, if you give them a few seconds to run the circuit and adjust for input from the sensors they start more reliably. Though I admit the factory says it does this thousands of times a second, reading intake air temperature, etc, knock sensors, all of it has to happen at the speed of electricity for these trucks to run right.
 

Pinger

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Seeing as Thinger has broached the electrical side of things.... Something a guy (who'd spent his working life maintaining medical X-ray machines) said has come back to me. Before attempting a cold start it is better to switch on another load (eg, headlights) for a short while (15 seconds say) as this supposedly 'prepares' the battery for the big cranking load.
I have no idea if this is true but it did come from someone who had a firm grasp of electrical fundamentals.
 

Erik the Awful

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If it's cranking slow, quit trying until you can fix the slow cranking. Either charge the battery, clean/fix the terminal ends, or preheat the block. Otherwise you're just doing more damage.

Here in Oklahoma the NWS has a better reputation, borne out of many years of studying tornadoes and the conditions that lead to them. Fifty years ago there was no warning for tornadoes, but now we can usually tell hours in advance that the conditions are leading to it.
 

HotWheelsBurban

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Seeing as Thinger has broached the electrical side of things.... Something a guy (who'd spent his working life maintaining medical X-ray machines) said has come back to me. Before attempting a cold start it is better to switch on another load (eg, headlights) for a short while (15 seconds say) as this supposedly 'prepares' the battery for the big cranking load.
I have no idea if this is true but it did come from someone who had a firm grasp of electrical fundamentals.
Yes I have heard that too, Dad did that when it was really cold. Said it "wakes up" the battery, was what he'd been told. When he was young, the family had an old and trustworthy shop and mechanic they used on their cars(this was in the 50s). That guy imparted a lot of advice to my Dad, and I remember some of it!
 

Vikingdude

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Yes I have heard that too, Dad did that when it was really cold. Said it "wakes up" the battery, was what he'd been told. When he was young, the family had an old and trustworthy shop and mechanic they used on their cars(this was in the 50s). That guy imparted a lot of advice to my Dad, and I remember some of it!
I don't know enough to tell if this is an old wives tale, or true science, but I'm definitely going to try it.
 
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