Fast idle on a cold Cummins diesel?

[J&JD]

Add that to also wondering if the full wall slide will come in when I push the button so I can leave the campground.

Amen to that!

 

[Neal]

It's been around or below freezing here in Nappanee (hopefully today is my last day of service) but 60's in the afternoon. While we have a few threads going on with similar topics, I can say the glow light has only been on a few seconds at most. This is probably also because the engine is not cold soaked, prior day of being indoors all day, etc. or having been driven all play in as to when to use your block heater as discussed. Just doing an overnight into cold weather doesn't mean your engine is that temp.

As to fast idle, I have not had my engine start and go into fast idle when cold, until this morning. As I type this my engine is in fast idle and it's interesting it's staying there so I'm not sure if a regen is going on as FL really doesn't show you those, it does its thing when it needs to. So either it's fast idling due to cold temps or its doing a regen, but this is the first time it's gone into fast idle at startup for me while here.

Edit: Normal idle now after approx 5 mins of fast idle.

 

[Rich W.]

It's been around or below freezing here in Nappanee (hopefully today is my last day of service) but 60's in the afternoon. While we have a few threads going on with similar topics, I can say the glow light has only been on a few seconds at most. This is probably also because the engine is not cold soaked, prior day of being indoors all day, etc. or having been driven all play in as to when to use your block heater as discussed. Just doing an overnight into cold weather doesn't mean your engine is that temp.

As to fast idle, I have not had my engine start and go into fast idle when cold, until this morning. As I type this my engine is in fast idle and it's interesting it's staying there so I'm not sure if a regen is going on as FL really doesn't show you those, it does its thing when it needs to. So either it's fast idling due to cold temps or its doing a regen, but this is the first time it's gone into fast idle at startup for me while here.

Edit: Normal idle now after approx 5 mins of fast idle.

It won’t do a parked regen on its own, only passive and active, and when you do a forced regen you get the HEST lamp. So this would be fast idle due to low temp.

I recently learned the difference between “Parked” and “Forced” regens. I‘ve been using the terms interchangeably because for me they are one in the same, but technically a parked regen occurs when you use the regen switch on the dash on commercial trucks or the shorting plug under the dash on RVs (because we can’t be trusted with a switch on the dash?). A forced regen is when you use some other diagnostic device to activate a regen. Of course you can only do a forced regen when parked, so…? Anyway in this case since the rig will only do passive and active regens on its own and you didn’t activate a parked regen, I’d say it was temp initiated fast idle.

Edit: According to all I’ve read, parked and forced regens take at least 45 minutes (mine have all been over an hour) and given your edit just now, it went to fast idle for some other reason. The first time mine did that I thought something was wrong it, but there are several other reasons it will do that.

Also while active regens occur in the background with no indicators on the dash alerting the driver, when you interrupt an active regen by stopping or getting off the highway and driving slower on secondary roads, you will get the illuminated indicators (DPF and/or HEST lamp) on the dash and an audible warning chime.

 

[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

Thanks to Neal’s “idle curiosity”, I’ve done a lot of reading on this in the last couple days and have drawn a few conclusions I think are useful:

• The big issue with extended idling is doing so at lower engine temps. I’ve seen 130° and 140° and below mentioned in various documents. There are some conflicting opinions about this with regards to modern fuel systems but I’ll err on the side of caution.
• Fast idling is said to address the issues associated with low engine temp (low combustion chamber temp) and cold oil at start up, and of course allows the rig to air up faster. Since we have the capability and its better than regular idle, I’ll use it.
• While Cummins says no warm up period is necessary as long as you don’t run under high load during warm up, I don’t want to start driving immediately on a cold engine and it seems fast idle for a short time (after oil pressure is up) would be preferable when idling a cold engine
• Extended or excessive idling, while not defined clearly anywhere, would seem to be anything over an hour based on my interpretation of sections of the Cummins operators manual.
• Since fueling only takes 10-15 minutes, and typically occurs when already at normal operation temp (190° minimum) I don’t see any problem with idling during fueling or any need for fast idle during the process.
• Any concerns about the DPF and idling are unfounded as long as the operator understands the regen process.
• Since the SCR and DPF reduce emissions primarily to nitrogen and water there is no legitimate environmental concern other than noise pollution. A little courtesy should alleviate that.

So that’s about it for me. I’ll idle long enough at start up to at least start warming the engine, and I’ll start doing so at high idle shortly after I have oil pressure (this will be new for me but I’m convinced). I’ll continue to idle while fueling for reasons previous stated at regular idle, and I’ll continue to idle for five minutes or so before shutting down to cool the turbo even though this may not be necessary depending on how I was driving before shut down. That should about cover it. This has been a good exercise for me and once again proves the value of this forum.

 

[Kevin D Pem]

Thanks to Neal’s “idle curiosity”, I’ve done a lot of reading on this in the last couple days and have drawn a few conclusions I think are useful:

• The big issue with extended idling is doing so at lower engine temps. I’ve seen 130° and 140° and below mentioned in various documents. There are some conflicting opinions about this with regards to modern fuel systems but I’ll err on the side of caution.
• Fast idling is said to address the issues associated with low engine temp (low combustion chamber temp) and cold oil at start up, and of course allows the rig to air up faster. Since we have the capability and its better than regular idle, I’ll use it.
• While Cummins says no warm up period is necessary as long as you don’t run under high load during warm up, I don’t want to start driving immediately on a cold engine and it seems fast idle for a short time (after oil pressure is up) would be preferable when idling a cold engine
• Extended or excessive idling, while not defined clearly anywhere, would seem to be anything over an hour based on my interpretation of sections of the Cummins operators manual.
• Since fueling only takes 10-15 minutes, and typically occurs when already at normal operation temp (190° minimum) I don’t see any problem with idling during fueling or any need for fast idle during the process.
• Any concerns about the DPF and idling are unfounded as long as the operator understands the regen process.
• Since the SCR and DPF reduce emissions primarily to nitrogen and water there is no legitimate environmental concern other than noise pollution. A little courtesy should alleviate that.

So that’s about it for me. I’ll idle long enough at start up to at least start warming the engine, and I’ll start doing so at high idle shortly after I have oil pressure (this will be new for me but I’m convinced). I’ll continue to idle while fueling for reasons previous stated at regular idle, and I’ll continue to idle for five minutes or so before shutting down to cool the turbo even though this may not be necessary depending on how I was driving before shut down. That should about cover it. This has been a good exercise for me and once again proves the value of this forum.

Sorry, I had to laugh. It struck me funny to hear a recommendation about high load conditions. With my trusty PU they tell me to push the tow/haul button when under heavy load to save the transmission. Many think they should push that button when towing. But the manual, and the button clearly state when you haul you should press that button.

SO!

An RV is close to full capacity without a single owner item. Does this mean you need to warm up, just because of the nature of the beast?

How close to that 80% of capacity are you loaded? Or is that heavy stress conditions?

Enquiring minds want to know!!!

 

[MemoriesByTheMile]

Thanks to Neal’s “idle curiosity”, I’ve done a lot of reading on this in the last couple days and have drawn a few conclusions I think are useful:

• The big issue with extended idling is doing so at lower engine temps. I’ve seen 130° and 140° and below mentioned in various documents. There are some conflicting opinions about this with regards to modern fuel systems but I’ll err on the side of caution.
• Fast idling is said to address the issues associated with low engine temp (low combustion chamber temp) and cold oil at start up, and of course allows the rig to air up faster. Since we have the capability and its better than regular idle, I’ll use it.
• While Cummins says no warm up period is necessary as long as you don’t run under high load during warm up, I don’t want to start driving immediately on a cold engine and it seems fast idle for a short time (after oil pressure is up) would be preferable when idling a cold engine
• Extended or excessive idling, while not defined clearly anywhere, would seem to be anything over an hour based on my interpretation of sections of the Cummins operators manual.
• Since fueling only takes 10-15 minutes, and typically occurs when already at normal operation temp (190° minimum) I don’t see any problem with idling during fueling or any need for fast idle during the process.
• Any concerns about the DPF and idling are unfounded as long as the operator understands the regen process.
• Since the SCR and DPF reduce emissions primarily to nitrogen and water there is no legitimate environmental concern other than noise pollution. A little courtesy should alleviate that.

So that’s about it for me. I’ll idle long enough at start up to at least start warming the engine, and I’ll start doing so at high idle shortly after I have oil pressure (this will be new for me but I’m convinced). I’ll continue to idle while fueling for reasons previous stated at regular idle, and I’ll continue to idle for five minutes or so before shutting down to cool the turbo even though this may not be necessary depending on how I was driving before shut down. That should about cover it. This has been a good exercise for me and once again proves the value of this forum.

Nice summary.

Only other item I would add - beyond the physics mentioned - some states have laws prohibiting idling for more than 5 minutes. Though idling for 10-15 minutes may not hurt the engine, it may attract unwanted attention from law enforcement. Or if you get a stare while idling this MAY be a reason.

 

[Rich W.]

Having been in law enforcement myself and being very close to many others in law enforcement my entire adult life I can confidently say that you would never attract the attention of law enforcement by idling unless someone complained enough to get a response, and then the most that would happen would be a very polite request to curtail whatever was irritating the complaining party so the responding officer could attend to more important matters.

 

[Rich W.]

Sorry, I had to laugh. It struck me funny to hear a recommendation about high load conditions. With my trusty PU they tell me to push the tow/haul button when under heavy load to save the transmission. Many think they should push that button when towing. But the manual, and the button clearly state when you haul you should press that button.

SO!

An RV is close to full capacity without a single owner item. Does this mean you need to warm up, just because of the nature of the beast?

How close to that 80% of capacity are you loaded? Or is that heavy stress conditions?

Enquiring minds want to know!!!

High load would be any time you need full throttle to accomplish whatever you're trying to do, such as grades, or constant start and stop while pulling a heavy load. Anyone driving a DP knows what this is from experience. Tow/haul on the other hand is for drivers who would otherwise experience a transmission constantly hunting or burning up their brakes because they leave it in overdrive. In fact Ford sadly went so far as to replace the “OD off” button with a “tow haul” button around 2008 or so. OD off was much more useful.

 

[Roadglide117]

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?

I always fast idle mine if my engine is running. When it's a cold 1st start i wait a couple minutes, oil pressure up..if I've been running and stop to grab something quick I raise the idle. Had semi trucks, past practice, would get over million miles on those.