Colder = Less Crank Time?

[mike7139]

Why does my car start up super fast the colder it is outside? For instance on an average morning the car takes around 2 seconds(guesstimate) of cranktime for the engine to fire up but today it was in the single digits and all it needed was like 1/2 a second of cranktime for the engine to fire up.

I have owned the car 15 years now and every year always wondered why this happens.

Can anyone explain?

 

[oilpsi2high]

Denser air.

 

[mike7139]

Originally Posted By: oilpsi2high
Denser air.


Is this more of a humidity/dewpoint type of thing or does it deal with actual temperature?

 

[01rangerxl]

Most likely it's just the way the computer is programmed to deal with a cold start.

My truck is the opposite. In warm/hot temps it fires pretty much immediately. Just bump the key and it's running. In the cold it sometimes cranks a couple times before firing.

 

[oilpsi2high]

Originally Posted By: mike7139
Originally Posted By: oilpsi2high
Denser air.


Is this more of a humidity/dewpoint type of thing or does it deal with actual temperature?


No idea, just a guess based on how an engine works.

 

[Clevy]

Colder air is more oxygen dense and I'm assuming gas the engine senses cold the start up fuel charge is more rich.
Just spitballing.

 

[justalubetech]

All the sensors are telling the computer the engine is cold, and gives it a richer mixture. Some engines even have a cold start injector that does nothing but spray in extra fuel when first starting the engine when cold.

 

[Clevy]

Originally Posted By: jsfalls
All the sensors are telling the computer the engine is cold, and gives it a richer mixture. Some engines even have a cold start injector that does nothing but spray in extra fuel when first starting the engine when cold.



What engines are those that come with the extra injector for cold starts?

 

[Lyman]

My truck always fires right away on cold mornings. In the afternoon when I am leaving work it takes a few revolutions. Just the computer doing it's job.

 

[abycat]

Originally Posted By: mike7139
Why does my car start up super fast the colder it is outside? For instance on an average morning the car takes around 2 seconds(guesstimate) of cranktime for the engine to fire up but today it was in the single digits and all it needed was like 1/2 a second of cranktime for the engine to fire up.

I have owned the car 15 years now and every year always wondered why this happens.

Can anyone explain?


Come up here when it's minus 45 out I bet your car will start slow ha ha. Very slow!

 

[JHZR2]

My vehicles are all the opposite. Which makes sense... Cold battery means lower voltage, which means slower spinning starter, possibly weaker spark, etc. Plus less volatile fuel.

So Id guess that there is some adaptation that is in the ECU to assist starting.

 

[01rangerxl]

Originally Posted By: Clevy
Originally Posted By: jsfalls
All the sensors are telling the computer the engine is cold, and gives it a richer mixture. Some engines even have a cold start injector that does nothing but spray in extra fuel when first starting the engine when cold.



What engines are those that come with the extra injector for cold starts?


A lot of older GM engines with early multiport injection had a cold start injector, like late 80s F-Bodies.

 

[abycat]

Originally Posted By: 01rangerxl
Originally Posted By: Clevy
Originally Posted By: jsfalls
All the sensors are telling the computer the engine is cold, and gives it a richer mixture. Some engines even have a cold start injector that does nothing but spray in extra fuel when first starting the engine when cold.



What engines are those that come with the extra injector for cold starts?


A lot of older GM engines with early multiport injection had a cold start injector, like late 80s F-Bodies.


I think some fords and imports too.

 

[mike7139]

Originally Posted By: abycat
Originally Posted By: mike7139
Why does my car start up super fast the colder it is outside? For instance on an average morning the car takes around 2 seconds(guesstimate) of cranktime for the engine to fire up but today it was in the single digits and all it needed was like 1/2 a second of cranktime for the engine to fire up.

I have owned the car 15 years now and every year always wondered why this happens.

Can anyone explain?


Come up here when it's minus 45 out I bet your car will start slow ha ha. Very slow!



The coldest the car ever seen was -21 and thats when I lived in northeast ohio. I am sure -40's will put a strain on everything.

 

[Vikas]

two second of cranking? That is a L O N G crank time!

 

[dlundblad]

Originally Posted By: Vikas
two second of cranking? That is a L O N G crank time!


Renix 4.0 engines are notorious for this. Lol.

 

[artificialist]

Often when the coolant temperature is low, the IAC motor is in the most open position. When the engine reaches operating temperature, the IAC is often more closed, and that causes a longer start. If the TB and IAC are dirty, that makes the engine even harder to start.

 

[SwampSurvivor]

My Cherokee always fires off pretty quick. Usually 5-6 revolutions of the starter in the warm.

In the winter when it's super cold, it usually starts up after the 1st revolution of the starter.

Of course, it cranks so slow that it's about as long as it is in the summer. I think I could spin it over quicker if I had a recoil on the crank pulley!

 

[fdcg27]

Originally Posted By: Clevy
Originally Posted By: jsfalls
All the sensors are telling the computer the engine is cold, and gives it a richer mixture. Some engines even have a cold start injector that does nothing but spray in extra fuel when first starting the engine when cold.



What engines are those that come with the extra injector for cold starts?


I've seen these on old VWs. They were called the cold start valve. Unless they worked, the engine simply wouldn't start. If you could get it to start with ether or by spraying gasoline down the intake or by tow-starting the car, it would then run just fine. Had this experience with a college buddy who had an old Type III.
I don't recall whether our '81 Vanagon had such a thing or not.
It did start without issue in below zero F weather and it did have a fairly old-school Bosch FI system with a computer the size of an eight track tape cassette, along with points in the distributor.

 

[Traction]

You wouldn't even give it a second thought, if you grew up with carbs, iffy chokes, and 30W oil.