Fast idle on a cold Cummins diesel?

[Neal]

I've watched some start their coaches in the morning and go straight to fast idle. Raises an eye brow a little for me, is that really good for a cold engine? Seems I'd want to let it idle and get fluids flowing first, warm up, then go high idle if needed

Any opinions on fast idle on a cold engine or shortly after starting?

 

[JRS]

I'll go to fast idle after oil pressure buildup + 30-60 secs. Experienced diesel mechanic said to keep idling to a minimum.

 

[Rich W.]

Fast idle is still only around 1000rpm with no load so its harmless but I too would wait a few minutes before doing it if at all. I imagine they were just in a rush to air up, but I’m never in that much of a hurry. Maybe they think less idle time is better so they are doing it at a higher speed for a shorter time? Doesn’t make sense but ya never know.

 

[Rd1]

This is another misnomer now a days. You 'may' have noticed, when you first start your engine, if it iscool enough temps outside, the engine ECM hi-idles for a brief period of time and then drops down to regular idle. Thats all it needs.

With new engines and ECM, I don't see any use for hi-idle as Rich says. The ECM takes care of what needsto be done. The old diesels had to be hi-idled to keep thing inorder.

Even for stops, ie fuel, I let the engine idle for even as long as 30min or whatever. The regular idle helps to stabilizes the engine and transmission temp, the turbo, etc.. when the engine is turned off for that 10-30 min or so of stopping, some parts of the engine may stay warmer than others. To me, thats more concerning than letting it idle for long periods.

I do the same when reaching camp, it idles for a long time while I get things hooked-up. Likewise when leaving, it idles while I get things secured.

When traveling long distances, Itypically covered 5-8 hrs of driving. Before planned stop, I'd easeup for some period of time to let things cool of some, before hitting the exit. Same after getting back on the hwy, I''l keep ez depending on weather, etc, Till all warms up evenly, before hitting the cruising speed!

 

[JRS]

Mine doesn't high idle at first than drop down.
The experienced mid 30's mechanic who told me (he was a camper nearby) a couple times during our stay not to idle new diesels with the new emission systems for long periods of time and to keep idling to a minimum. He suggested fast idling when you have to idle. Also said it's one of the worst things you can do to these new engines which actually surprised me when he told me that....
IMHO, by the time you get off the hwy exit and to the campground office the engine has cooled off. I shut down when checking in.
To each his own

 

[MemoriesByTheMile]

Fast idle is part of the standard air brake test procedure, when testing that the compressor builds up the pressure between 2 different pressure points in less than a certain time.

There seems to be some variance between different tests, but the one we use we check that the pressure builds between 50 and 90, while using fast idle, in less than 3 minutes.

I will give the engine time to build oil pressure before fast idle, but that is typically less than 30 seconds.

What makes me raise my eyebrows is diesel engines idling more than 5 min when most manuals that I have read state they should not idle for more than a couple minutes — except when cooling down after leaving highway or heavy load use.

 

[Rich W.]

if you can ignore all the pop-ups and ads, this seems like a fairly balanced discussion on the topic:

What Is Diesel High Idle and When Should You Use It?

If you drive a diesel RV, you may be aware of diesel high idle (sometimes referred to as "fast idle"), and your rig may even have a high idle mode or

www.thervgeeks.com

 

[CaptainGizmo]

FWIW, these are the Standard protocols I’ve learned for the most extreme use…Fire engines and trucks. Our rigs were under the strict care of certified mechanics; Detroits, Cummins, and CATS.

- Engine heater to keep block and fluids warm
- Idle until pressures are built up before hit’n it
- After load, do not shut down immediately

Of course, we had hours of near idling; rarely using fast idle.

These diesels are beasts and will tolerate “constant RPM” running for days…just think of a generator!

This said, the DEF system keeps clean with HEAT. And in the middle of a REGEN, the procedure is to let idle for 45 minutes, it it’s not being driven.

So…Carry on…our “RV” usage is pretty weak-toast compared to what these engines can take.

 

[Rich W.]

Since this discussion began I’ve developed a few concerns as follows:

1. Soot build-up in the EGR
2. Cylinder wash
3. Varnishing of combustion chambers (I just found this one to add to the list)

I’ll continue researching all of the above. One thing I’m not concerned about is the DPF - having the ability to perform regens negates any concerns here.

The modern fire engines we operated idled for hours on scene as Captain Steve stated although we were also periodically advised against extended idling. But there are some major differences with those rigs: they were exempt from any emissions related derate functions, they had constant care by the city garage, any time we had an issue we could just swap into a reserve unit, and while they were in service for 12 years before rotating to reserve status, they never developed very high milage because we didn't travel that much in them - a few strike team trips around the state each year but primarily local response. Operators were never worried about long term impacts of idling. We might need to pay closer attention to the issue.

All that said, I won’t shut down at a fuel island, and while I’ve recently read some comments about idling while checking in to a park being “bad manners”, generally speaking the entrance of a park is far enough away from occupied campsites that the concern seems unwarranted. I’d rather wait until I’m parked for the day before shutting down, avoiding unnecessary starts and stops, and ensuring that I won’t be stuck somewhere I don’t want to spend the night (or longer).

But as I said, I’ll revisit all of this and I hope others will add their insights, practices, and experiences.

 

[jbh]

Generators and pumps are running at speed under load, not idling.

 

[JRS]

Rich, thanks for the post and look forward to hearing what you end up finding. I'm going to continue keeping idling to a minimum at this point. After cool down which doesn't take long, I even shut down while fueling. When I fast idle, it's typically 1100-1200rpms. Naturally I wish I didn't have to fast idle but currently think it's best based on what I've been told and read

 

[ARD]

All that said, I won’t shut down at a fuel island, and while I’ve recently read some comments about idling while checking in to a park being “bad manners”, generally speaking the entrance of a park is far enough away from occupied campsites that the concern seems unwarranted. I’d rather wait until I’m parked for the day before shutting down, avoiding unnecessary starts and stops, and ensuring that I won’t be stuck somewhere I don’t want to spend the night (or longer).

I used to turn my engine off and on everywhere, but after having to replace 2 DEF heads, one in my DS and one in my LA, I prefer to let the engine idle. Perhaps I'm a little traumatized , but I am in total agreement with @Rich W. I find it very hard to believe that the little bit of idling I do will have any bad effects on the engine.

And when I get to my site, I let it idle further as my Newmar tech recommends to keep the engine idling while running out the slides - even when connected to shore power.

As far as going to high idle on a cold engine, I was taught at my Newmar CPU and Spartan Owner's to go to high idle. If I know it is going to be cold the next day, I turn on the block heater the night before. Also, I have noticed when it is cold outside, my engine will not immediately go to high idle no matter how much I coax it. It will run for a bit and idle higher in its own time, not mine. I swear it's possessed.

 

[Rich W.]

Rich, thanks for the post and look forward to hearing what you end up finding. I'm going to continue keeping idling to a minimum at this point. After cool down which doesn't take long, I even shut down while fueling. When I fast idle, it's typically 1100-1200rpms. Naturally I wish I didn't have to fast idle but currently think it's best based on what I've been told and read

I recently read a post on the FB Newmar owners group about shutting down at a fuel island and then not being able to restart. I think it was a DS with solenoid problem, but the short-term issue was being stranded at the fuel island, unable to re-start and move for an extended period of time. That seems like it would be very unpleasant.

 

[Bigblockyeti]

I put some miles on a new (at the time) 2006 International 4300 with the DT466E and if someone forgot to plug it in the night before, and often if it was plugged in, it would go to high idle by itself when the temperature was 20°F or less. The only way I could prevent it from going to high idle was setting the cruise control/idle speed to the 700rpm minimum, this was available to control the PTO speed for the hydraulic hoist. Years later I worked on a number of CAT C12, C13, C7, C9, Cummins M11, 4bt 6bt, Detroit Diesels, Volvo diesels, Mercedes diesels and Mack diesels. All of these were pre-DEF and most were in offroad equipment. Many of those that were electronically controlled would default to a high idle right after startup when it was cold outside, regardless of whether or not they were plugged in. Plugging them in only serves to heat up some of the engine coolant and does little to nothing for the 10-20 gallons of engine oil, 20 gallons of transmission oil and up to 100 gallons of hydraulic oil some equipment had. The high idle for those applications was to get the fluids moving so they could start making money.

 

[J&JD]

And when I get to my site, I let it idle further as my Newmar tech recommends to keep the engine idling while running out the slides - even when connected to shore power.

Unfortunately, my 2017DS will not allow the slides to work with the engine running. Just as well as I’m not a fan of idling either the DS or any of my gas powered vehicles for that matter. My brain just can’t seem to accept the continuous burning of fuel when it’s not needed. And I’m not much of a fan of listening to diesel’s idling next to me for extended periods at either the fuel island or campsite but that’s just cantankerous old me.
Back to the OP’s question, it seems reasonable to me to enter fast idle within 30 seconds or so after oil pressure is up in my humble totally amateur opinion.

 

[Texas Clodhopper]

I recently read a post on the FB Newmar owners group about shutting down at a fuel island and then not being able to restart. I think it was a DS with solenoid problem, but the short-term issue was being stranded at the fuel island, unable to re-start and move for an extended period of time. That seems like it would be very unpleasant.

I suspect if that were to happen to me, stranded at the fuel island, that there would be some cantankerous driver behind me who would be more than happy to give me a push.

 

[FLSteve]

All that said, I won’t shut down at a fuel island, and while I’ve recently read some comments about idling while checking in to a park being “bad manners”, generally speaking the entrance of a park is far enough away from occupied campsites that the concern seems unwarranted. I’d rather wait until I’m parked for the day before shutting down, avoiding unnecessary starts and stops, and ensuring that I won’t be stuck somewhere I don’t want to spend the night (or longer).

@Rich W. @ARD ... This is pretty much the way I operate as well.

FLSteve

 

[J&JD]

I recently read a post on the FB Newmar owners group about shutting down at a fuel island and then not being able to restart. I think it was a DS with solenoid problem, but the short-term issue was being stranded at the fuel island, unable to re-start and move for an extended period of time. That seems like it would be very unpleasant.

There are so many worse places where not being able to start the engine could be much more problematic than one lane of a fueling area. At least there is a good possibility of professional help nearby. Do most people worry about whether the engine is going to start each time they try to start or shutdown?

 

[Rich W.]

There are so many worse places where not being able to start the engine could be much more problematic than one lane of a fueling area. At least there is a good possibility of professional help nearby. Do most people worry about whether the engine is going to start each time they try to start or shutdown?

Well part of that is the embarrassment factor of taking a fuel lane out of service that truckers are expecting to be able to use, and part of it is 45 years in the fire service where we never shut down until we were back in the barn. So no I don’t worry about it, but I also am somewhat more risk averse than “normal” people and have somewhat different habits.

 

[FLSteve]

Do most people worry about whether the engine is going to start each time they try to start or shutdown?

@J&JD ... not sure it rises to the worry level, but it sure does cross my mind each time. Add that to also wondering if the full wall slide will come in when I push the button so I can leave the campground.

FLSteve