revving the motor while cold?

[sootman73]

okay im trying to explain to someone why it is that they should not rev the motor up while it is cold. he started it(very roughly) at 11*F. what is the reason that you should not rev it? i know not to just not sure why.

 

[redneckaggie]

the oil pump hasn't kicked in yet the engine just hasn't "smoothed out" is what i have always heard.

 

[sootman73]

heres what the guy im arguing with says.

"Your owners manual explicitly states "Do Not Press The Gas While Starting. Do Not Press The Gas Until The Oil Pressure Is At Normal Reading." Why not rev it? That's the only thing that warms it up. It can smoke for half an hour idling or you can drive it fifty feet and it'll be good to go."

heres his video on you tube.

http://www.youtube.com/watch?v=WLLuoHLaT-Y#QsM7ztOshuY

 

[6 Nebraska IDIs]

That guy's an idiot. If he's a member here or a friend of yours, Im sorry, but that motor wont last long at that rate. He did a number of things wrong. First was that he cranked on it for longer that 45 seconds before stopping, then he went right back to glow plugging it, then started cranked it again with less than 30 seconds of cool down time for the starter, then he floored it over and over and over again when it was obvious that it was only running on a few cylinders.

Biggest reason to not rev for a few minutes after start up is oil is not pumped through the entire engine (if that thing's a turbo diesel kiss it goodbye), second, especially when cold, is that the oil is VERY thick when its cold and it puts an extreme stress on all rotating parts, including the oil pump. And Im sure there's a few others.

 

[sootman73]

no he isn't a friend of mine just some video i found and it made me mad watching it get killed like that.

 

[Ottoparts]

I didn't watch the whole video, but is it me or is that not running on all 8 anyway?

 

[Cheaper Jeeper]

6NebIDIs pretty much covered it. When the engine sits almost all the oil drains into the pan. When you start it it takes a few seconds for all the empty oil passages to get filled back up - especially when it is cold.

Until the oil passages all get full of oil and you have good stable oil pressure you have metal on metal in all the crank, main, & rod bearings. During normal operation high pressure oil actually forms a cushioning layer between the bearings and rotating parts to where they don't actully even touch each other. If you don't wait until the pressure is up before you start to rev it, you are putting all the stress of revving it on the bearings while the parts are still metal on metal - before that cushion of high-pressure oil is there to keep them from actually touching.

This dramatically accelerates wear in the bearings, and as we all know, it only takes a few thousandths of wear in the crank and/or rod bearings before things start coming apart....

 

[rubberfish]

And I agree, his starting procedure needs a bit of correction.

 

[sootman73]

does it really say that? must be towards the end as i didn't watch it all the way through. had to comment it and tell him to change his procedure.

 

[Russ]

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Here's the typical oil route thru a engine. When it's not running most of the oil is in the pan, the oil doesn't start to move until the oil pump turns. It takes a few revolution of the oil pump to get oil to the top of the engine. While it the oil is getting to the top of the engine, all of the top end parts(valve train) are only being lubed by any residual oil left there from the previous run time. If it's his engine he can run it any way he wants. Just don't touch my truck.

 

[redneckaggie]

smoke for half an hour idleing? he's got some problems there anyways i would think though i have never started at below about 34.

 

[rubberfish]

does it really say that?

Yup. But who cares.
I was just taking a jab at some of the boys.
Because if it had been me that posted it......

 

[rubberfish]

If it's his engine he can run it any way he wants. Just don't touch my truck.

That's kind of how I thought of him.
It's his truck and money.....but

 

[funnyman06]

"Your owners manual explicitly states "Do Not Press The Gas While Starting. Do Not Press The Gas Until The Oil Pressure Is At Normal Reading." Why not rev it? That's the only thing that warms it up. It can smoke for half an hour idling or you can drive it fifty feet and it'll be good to go."

My truck tells me to give it have or full throttle when starting it, depending on how cold it is? Is it normal to give it half throttle when starting it?

 

[rickrat]

On my visor it says the same thing, it says to give it half throttle when starting, or if it is below 32 degrees to give it full throttle.

I never do though, I usually dont give it any throttle at all, however, while the glow plugs are warming up, I will depress the accelerator to get the high idle solonoid engaged.