Cold Start Idling?

[d9]

Does it make any sense??



From what others have posted, it seems that idling a cummins at any temp BELOW normal operating temp risks cylinder washdown and dilution of crankcase oil with diesel fuel.



So why the heck does Dodge recommend the following (Upon cold starts), (Stated under the flip down sun visor):



"When the engine starts, depress accel. pedal and allow engine speed to increase to approx. 1000 rpms. Then allow it to return to idle. Allow engine to idle for 30 seconds. "



My main question:



What is Dodge's reasoning in this cold-start recomendation? I can understand the "bring your engine to 1000 rpms" for a couple of seconds. Do that for the same reason some guys use sticks and high-idle adjustments to put the engine under load to kick-start crancase oil circulation and engine warmup. But why only for a couple of seconds and then "Allow engine to idle for 30 seconds"



On a frosty 25 degree morning, Allowing my big baby to idle for 30 seconds before I let her out of the gate seems rediculous, potentially damaging, and contrary to the popular wisdom of the TDR. What do you all think? What is Dodge thinking? Thanks!!

 

[Power Wagon]

Not a bad idea at all.



30 seconds of idling isn't going to wash down anything. With the great injection technology in use today, there's no smoke, no washing down, or other ill effects from 30 seconds of idle.



I believe they want you to do that for purposes of getting the oil circulating, the transmission fluid circulating, and stabilizing the internal temperatures a bit - stone cold parts don't fit as well as warm ones.

 

[Sticks]

DC warns against idling for more than 5 minutes (or was it 15?).



Before I was educated in the bad things that can happen from extended idling, I can say that the truck will NEVER warm up from idling, and will cool well below 180 if it is warm. On my first truck when I was working graveyard during the winter months, I would go out and start my truck 15 - 20 minutes before I would be punching out for the night, and when I got out to my truck, the temp gauge would still be pegged below 140* and the heater blowing nice frosty air.



Now I have an exhaust brake, and idle for 1 -2 minutes with it on before I head out (if the temps are below freezing).

 

[Coalsmoke]

What about those people who will take a nap in a really cold climate and let their truck idle fo 3-4 hours at a time? they don't seem to have problems, can someone explain?

 

[Joe G.]

If they are like the truck we parked next to in an eastern Oregon road side rest they have some sort of automatic switch to fast idle when the EGT gets too cool. The idle went up on that truck every so often while we were there. Kept my wife awake.

 

[rbattelle]

The manual for my '03 actually tells you to idle for 3 minutes before driving off if the heater grids are cycling. I've gotten into the habit of idling it just until the heaters stop running (2 minutes, normally), then driving away.

 

[rbattelle]

Oh, and I have never done the "increase idle to 1000 RPM" thing because I absolutely cannot see the logic in doing so. Can someone explain it to me?

 

[Coalsmoke]

depending on the oil pump configuration (how much it is designed to flow at what rpm's) bringing the idle up a bit to 1000 ish gets the oil moving quickly through all the parts, such in our case the p7100 also drains oil, so it takes a bit of pressure to be primed to.

 

[FPoitra]

I always wondered about the cold starting procedure on the visor too. I guess it only makes sense to get the oil flowing quicker and thats about it. I still never did get a straight answer from other forums on how long is too long to idle our trucks. I idle mine for about 5-10 minutes in the mornings before I leave when the temp is under 20*. I hope that is not considered too long. And the high idle mode kicks in right away anyway, so I imagine that helps prevent cylinder washdown. But as already stated, with the technological advances in these trucks, they must have been engineered to withstand some idle time.

 

[FPoitra]

oh ya, and some people recommend that you start up, wait for oil pressure to increase, then take off. I just dont feel right doing that, especially when it is 10 below zero!

 

[Joe G.]

The business about long idling is about when the engine is warm. What they are talking about is like you see some big rigs sit for hours just idling while the driver sleeps or something like that.



The other thing is warm up for a cold engine. Consider this. The most wear happens when the engine is cold. So how to make sure the engine stays cold as long as possible so it wears the most it can? Warming it up by idling it that's how. The best thing is to warm it up as fast as possible without stressing the engine. Some people do this with an exhaust brake and fast idle. Others go as soon as they have oil pressure and take it easy until the heat gauge shows some temp.

 

[Billy Diesel]

Extended idleing, i. e. over 5 minutes, is bad only if you are at idle. A high idle isn't idle. At high idle, ~1200rpm, you can idle as long as you want, as the load on the engine is minimal, yet enough to build heat and prevent cylinder wash. Of course, if you have the factory high idle, it will kick off once you reach certain requirements, and it won't kick back in until it has sat in the cold for a long time.



When the truck is started in the morning, what is the difference between:

1. Start and let it high idle for 10 minutes

2. Starting, waiting for oil pressure, then driving easy

3. Start and let it idle for 10 minutes?



Well, numbers 1 & 2 are pretty close to the same, except that there is a chance of lugging the engine and idleing at stop signs/lights in #2, which isn't good. In #3, the engine temp never got much above outside temp, the defrosters aren't going to work any faster, the oil isn't flowing much better than when you started it, and there is a risk of cylinder wash. ***I prefer #1, but am forced to do #2 often as the factory high idle is set for too low an ambient air temp for my likeing. ***



As a side note, I don't do increase rpms to 1000 like the visor says. It will deactive the factory high idle, and it is hard to do with a remote start!

 

[Joe G.]

#2 is probably better since you will keep the EGT over 300 unless the wait at a light is a long one. The engine also will warm up sooner.



If you have an exhaust brake then #1 is very good. I don't think just a high idle with no exhaust brake in extremely cold weather is going to warm the engine up very fast.



Even in weather that is not very cold these engines take a long time to warm up. I was working a contract in Roseville, CA a couple of years ago. The commute from where I was staying in Sacramento was just a little over 20 miles. Most all of that was freeway. During the winter in what amounts to cold weather there (low 30s) it would take about 18 miles or so before the engine would get warm enough to open the t-stat and give me a little heat. Probably have to drive a lot further than that where it gets really cold. The EGT would be over 300 before I got to the on-ramp to the freeway which was about 200 yards or so.



My truck has 228K miles on it. No measurable oil use by the time I change oil at about 5K intervals. Even when I get lazy and let it go to 9K there is no oil use that I can detect with the dip stick. I know that it uses some out the blow by tube, but it's not much. Oil pressure is still at the relief valve pop off point except for idle after it is good and warm. Then the oil pressure is just a little below the middle mark on the gauge.

 

[Billy Diesel]

If you have an exhaust brake then #1 is very good. I don't think just a high idle with no exhaust brake in extremely cold weather is going to warm the engine up very fast.

Actually, the engine heats up faster in extremely cold weather, as the 3-cylinder-shutoff activates. A couple minutes of that, and it is nice and toasty in the cab. It also lets your neighbors know that you are up!



--

-Will

 

[WadePatton]

High idle stick

I have used sticks and pipes and firewood to mash on the footfeed to run the idle up.



Geno's sells a great little gizmo that hooks to the wheel and pushes on the throttle. CHECK it out. Works on 12 and 24's! and anything else with a steering wheel and accelerator.

 

[Cooker]

Those of use with 12v do not have the 3 cyl shutoff. A high idle on a cold engine does very little, IMHO, especially with the OEM fan on. Without a fan, with the grille blocked, and high idle and warm up is accelerated

 

[Coalsmoke]

I'll start, run up the rpms a little to get oil flow, then idle for about a minute with ex-brake on, then slowly be on my way. After a few minutes truck is starting to get warm and happy

 

[d9]

Visor recommendation

So it seems that everyone starts their truck in cold weather a bit differently. Some have exhaust breaks, some use the Geno's Garage gadgets, some rely on "factory high idle" (must be a 24 valve thang), and some get a move on right after ignition and "take it easy" until the coolant temp guage wakes up.



One thing is staying constant:



NO ONE IS FOLLOWING THE "COLD STARTING" PROCEDURE RECOMMENDED BY DODGE/CUMMINS BEHIND THE SUN VISOR!!



Who revs to 1000 rpms for a second, followed by normal 30 second idle?? Who trusts the recommendation?



IMHO, driving away gently, immediately after ignition, will much more effectively warm a cummins and prevent cylinder washdown than revving to 1000 rpms for 2 seconds and idling for 30 seconds (@~850 rpms) before driving.

 

[Mingoglia]

uhh ohh... what happens when you're in cold temperatures with a trailer? ... since starting out after the oil temp is up will result in lugging because of the weight.