Let it run, or shut it off?

[50+]

For as long as I can remember it been the norm to let a Diesel engine idle, rather than shut it down for short periods of time. Such as a 15 minute coffee stop, or even a 1/2 hr lunch break. I dont know why this is, or was, the normal thing to do, other than I know that older diesel engines years ago were a pain to start. And it saves on starters, and building up fuel pressure all over again etc. A friend of mine said he was told (dont know by who) that the worse thing you can do is let a diesel pickup set and idle. Even if all your doing is stopping for three minutes at the local Qwik shop. I usually let mine run if I'm not worried somebody will drive off with it. Any thoughts? And what do you do?

[JD Diesel]

Why let it run it has no purpose. It only wastes fuel the manufacture does not tell you to do this. So I say save the fuel and use it where you need it on the road. JD :rolleyes:

[Dewey Faircloth]

Usually let mine run,been driving diesels over 22 years any never had a problem.
Every one has their own thoughts on this,so just try what you think best.
When every one agrees we are in real trouble.

[Tough Guy]

Letting it run is fine, but letting the EGT's fall below 275F will not allow for proper combustion and it is possible to have "cylinder wash" occur...

The solution to this is an elevated idle, or "high idle" I am not sure about the LLY but a switch can be installed in the LB7's...Use the search function of the forum...

I let my 6.5L idle all the time, and other than wasting fuel I haven't suffered any ill affects.

Cheers

[DmaxMaverick]

I've owned/operated each model of GM light truck Diesels. Over several hundred thousand miles each (except the Duramax--working on that one), idling has not made a difference, other than fuel consumption. I've idled them for long periods of time, in all types of weather/temps. It gets so hot here in the summer, I usually idle my '01 for 20 minutes with the A/C on before taking off. It doesn't seem to noticeably effect my mileage. If it did, that extra $.50 of fuel is worth a cool cab.

The "cylinder wash" concern should not be an issue, in any case, with a pre-chambered Diesel. The cylinder wash warning has been around as long as I've been around Diesel engines, but I've never seen any effects from it. It is only recently that auto shut down timers have been incorporated into heavy duty engines as a requirement of the emmissions standards. Picked up a brand new Volvo OTR tractor a couple months ago. Idle in N for 2 minutes, and the engine shuts off. No overide or settings. Just shuts off. Back in my younger days when I was driving OTR, we shut them off when we went home, or had an extended layover. Started up in the morning, and, usually, never had to touch the starter button (starters had buttons then. If you turned the key like in a car, it broke) til the next morning. Never saw any issues of cylinder washing. Those were Cummins big/small cam engines. That's about as "direct injection" as you get and ran sloppy wet, and smoked like a freight train. They were known for "sucking" sleeves on ocasion, but there was no connection with long idling.

[Kennedy]

This is very popular with the Cummins guys as they must think they have a big rig. Personally, I let mine run quite a bit for warm up or climate control, but if neither are necessary, I shut it down, even for a 5 min run into a store.

I have a remote start with turbo timer so if it is hot I can leave it run, but typically I find that there is sufficient light load coast down to cool things.

Our trip to MT saw little down time, idling at every rest stop and during our single nap time (1.5 hrs) but shut down at meal breaks. Climate control and hot ambient conditions were the key issues here.

With the addition of our second (dyno) building, I typically park inside, but prior to this, I would start my 2002 via remote start to warm up and frequently got sidetracked only to have it time out 20+ minutes later. Warm or cold, I always let my vehicles warm up prior to driving them.

[madmatt]

It has been proven by Cat, Cummins, Detriot and Mercedes that unessacry idle time causes oil consumption and injector failures. Just to file for Warrenty on these engine we had to get a printout that included idle time. If you had a oil consumption problem or injector seize and the idle time was considered excessive...warrenty denined! I haven't heard of problems w/ the duramax and idleing, but if it wasn't hard on a engine, these other mfgs. wouldn't make such a deal of it. most now even have timers to prevent idleing for too long.

My opinion, Don't Idle unless warming it up or shuting it down w/ high egts.

[Jim Brzozowski]

I'm not a fan of letting any engine idle for a long period of time, but I doubt it really hurts the engine. At the place where I work, these guys start the Kenworths and Peterbuilts in the morning and don't shut them off until late at night every day year after year, course they aren't paying for the fuel out of their pocker either. Comfort has become more important for me than it used to be, so when traveling and stopped. I will keep that AC going, but I still blip the engine up off idle every so often out of habit.
Izusu could probably tell us what would happen if one started up a Duramax and let it idle for say 3 months and then shut it down, tear it down and check it out. Who wants to propose that to them?
Inquiring minds want to know.