Extended Idle / High Idle Revisited

[HC]

I know this topic has been touched on many times before, but I wanted to share what the Cummins PowerMaster said recently in reply to a question, because it provides an answer that is different than what I have heard before. Also, I believe it is different from information that others have reported in the past as coming from Cummins.



PowerMaster: Cummins does not recommend excessive idling of the engines because some people let them idle for hours, which can cause excessive carbon buildup on the pistons, piston rings, injector tips, valves, etc. Whenever coolant temperatures are below 160 degF, the diesel engine does not burn fuel very well and this causes the carbon buildup. Therefore, if you are only stopped for 10 minutes or so, it might be just as well to let it run, so the coolant temperature stays in the 140 to 160 degree range. At idle the engine will burn about 1/2 gal fuel per hour, which is not terribly expensive, plus your truck cab stays warm.



Question: Is it true that a high idler essentially eliminates the usual concerns [about extended idle] even under "no load" conditions?



Answer: No that is not true. The fuel will not burn completely and will cause the same type of problems (carbon build up on valves ,cylinders & heads) as if you idled at low RPM. It just takes a little longer at fast idle for the carbon to build up.



Question: Should I remain concerned and avoid idling even at increased engine RPM?



Answer: YES

We hope this helps and please let us know if you have other questions and if away from your computer, feel free to call us toll free at 1-800-DIESELS (343-7357).



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So, what do you think, folks?

 

[joesoot]

Mine idled for 3 hours last week when I locked the keys in it

After I got into the truck, I took it out on the freeway and ran the p*ss out of it hoping to cook out any deposits.

 

[SmokinJoe]

Originally posted by HC

Question: Should I remain concerned and avoid idling even at increased engine RPM?



Answer: YES

I think that an exhaust brake should cause the temps to stay at normal operating temperature, thus no buildup...

 

[Bigsaint]

I thought that high idling was the cure for a quick warm up on those winter days, even built a high idle stick to wedge between the front seat bracket and the go pedal. I would normally warm the truck up for 10 minutes or so, using this method and running the rpms up to 12-1300 or so. Seemed to work well, until I had the stock injectors out for a BOMB run. They looked like crap, to put it mildly. Heavy carbon build up. I had a total of 3200 miles on the truck.



When the BD step 3 injectors came out to make room for the 5's, the 3's were as clean as if they were new. The key, as Smokin Joe stated above, was using an exhaust break for a quick winter warm up, rather than a high idle, IMHO.



If you don't have an e-brake, just plug in when below 40 F if possible and do not work the engine hard until the water temp. comes up. If you have an e-brake, start the truck, let the oil pressure come up, flip on the brake and let her idle for 5-10 minutes.



I try to keep my idling down to 5 minutes or less in the summer, with the brake off. In the winter, I just activate the brake when idling for more than a minute or so. Works for me.



Scott W.

 

[EMDDIESEL]

I have the Adjustable High Idler in my 01' although i have not had it installed in the wintertime so i dont know just how fast it will warm the truck up. I will probably juts stick wioth the Plug in or hopefully an Espar heater.

 

[HC]

Thanks everyone for the input.



Scott, I think your observations on injectors, with and without the exhaust brake, were especially valuable.



I find it somewhat interesting that Cummins tells me in August that high idling is still bad, just not as bad as normal idle speeds, and then in September we see the new reflash that provides a factory high idle for cold weather. Seems inconsistent. I guess in Cummins' defense the question is a little different; the high idle reflash may improve warm up as the TSB says, but idling for hours is still risky.

 

[nps]

HC,



The difference between the factory high idle feature and a high idle stick on the go pedal is that the factory feature also shuts down 3 cylinders. That would suggest that the 3 inop cylinders get no fuel, thus no carbon buildup, and the 3 running cylinders get an even higher operating temp due to the extra work put on them in keeping the 3 inop cylinders moving.



I wonder if the factory feature puts more stress on the injection pump due to an imbalanced operating cycle.

 

[Murle]

All I can say is that my warranty is for 100,000 miles. It does not say how many hours I have to put on my truck. Sorry I'm not going to worry about how much my truck idles or how much it does not idle. They will warranty it.

 

[HC]

Originally posted by nps

The difference between the factory high idle feature and a high idle stick on the go pedal is that the factory feature also shuts down 3 cylinders...

I noticed that too, but, where I live that feature would rarely come into play since it doesn't get below 15 degrees but about once a year. There are many mornings where the low is near, but not quite below 32 degrees, so the factory ECM upgrade wouldn't engage at all most mornings.



Of course, then again, the factory ECM upgrade is probably "free" - can't beat that price!

 

[HC]

More "official" information from the Cummins Powermaster:

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Question: Is it OK to idle for extended periods with the exhaust brake engaged? All temperatures seem to be staying about where they would running down the road; for example, exhaust gas temperature is running between 500 and 600 degrees, so it seems like the only thing I need to watch out for would be overheating due to reduced air flow, but I'd like to hear the PowerMaster's official ruling!



Answer: Yes, the engine will overheat if cooling system (both air and coolant) is not working right. Using the engine brake is best way to idle for long periods of time.

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Well, at least I've solved my personal issues on which device to get. BOTH.

 

[JJW_ND]

THose of you that get to larger truck stops in the middle of the night in Northern states will find lots of hotshots idleing for hours on end. I would always pull in, get interior as hot as I could with heater. Shut down and sleep until I woke up freezing.



Cummins shops up here said the 24V cool down more when idleing the the 12V. It was rare to have stuck valves in a 12V (down not mean idleing was OK, just no obvious damage). This past winter lots of stuck valve issues. Several busses here in ND.



I am going to guess most problems develop when the the truck is first started and then left parked and idled for ever (school buses on game night). When everything is up to normal operating temp and one stops to idle, you could go allot longer before problems happen.



Bottom line is don't start until your ready to start driving. Shut it off when your stopped for a while. Running fanless and with winter front all help keep the heat in, got runner hard to build heat in the first place.



The only thing Cummins could have added to make the Cold idle feature better (if engine protection was the goal) is have it shut done the engine if high idle, cut fuel to cylinder still does not keep coolant temps at a minimum temp.



jjw

ND