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Old 04-29-2014, 11:39 AM   #21
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Gasoline has vapors which can be ignited by a spark, and cause a fire. This is why you should always shut down a gasoline engine when refueling, as tons of vapors are released during this process, and sometimes the outside air movement isn't enough to get vapors away from the vehicle. Diesel does not emit vapors like gasoline, and does not explode like gasoline, therefore does not have the same issues as gasoline.

Not sure about the duramax, but the Cummins on my truck has the automatic high idle feature which monitors exhaust temps and other factors of the SCR system. If they are not running optimally, the system will put the engine into automatic high idle. I can also set high idle manually, which I do when I notice it in regen and I'm about to shut the truck down. While you shouldn't let the truck idle for too long, idling when you're working the crap out of the engine shouldn't be a big deal in the long run. You're going to get right back on the freeway and get everything super hot again.
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Old 04-29-2014, 11:42 AM   #22
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Got links to back this up? It's news to me.
He's quite correct. It's a well known fact about SCR emissions systems. When exhaust temps aren't high enough, the system can end up creating too much soot through EGR, clogging DPF and making it so that DPF can't get hot enough to burn off the soot, making the entire system work inefficiently. Many of the newer trucks have high idle features which can help with this, especially when intake temps are low.
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Old 04-29-2014, 11:43 AM   #23
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Got links to back this up? It's news to me.
Sorry SKnight, I just seen this today.

What exactly are you wanting links to back up specifically?

I will do my best to provide!
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Old 04-29-2014, 07:42 PM   #24
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Your newer diesel you are better off not letting it idle too long. Typically if I plan to let mine sit for more than a couple of minutes I will shut it off. Any less and I will let it keep running.
The reason the newer diesels shouldn't idle is due to the new emissions they are installing. Idling is a rather inefficient process with diesels and creates a fair amount of soot and debris from unburnt fuel. The unburnt fuel will begin to plug your DPF filter and either your truck will go into regeneration to clean this filter or worse yet you may need to replace the filter. These filters do have a service life, a fairly long one, but idle time decreases their life.
Thats why they have a front and rear pressure sensor, to motor the condition of the DPF. When the pressure difference meets spec, it goes through a regen process to burn off that soot. The only problem occurs when you don't drive in conditions where a regen can happen, then a forced regen would have to happen but in general that's rare. It's what it's designed to do and pulling a heavy load makes more soot than idling does.

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Another down fall to idling for longer periods is that at an idle your fuel pressure isn't very high. Since the fuel pressure isn't very high the spray pattern from your injector isn't at its optimum patter and begins to flush the cylinder walls with diesel fuel. This can get fuel between the piston rings and the cylinder walls and can actually get into the oil.
False. Common rail systems idle at 6,000PSI plus. No worry about fueling issues there, next time you run across someone with a scan tool that has bi-directional control ask them to test the fuel pressure, a Duramax can make 21,000PSI+ at idle. If working properly, those concerns went out years ago, even mechanically injected diesels don't have that issue unless you've got injector problems.

That's why I asked for links, what you said runs counter to an awful lot of GM training I went through.

I'm not advocating never shutting down or leaving it idle during dinner, but you're not going to ruin your DPF or wash down your cylinders either.
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Old 04-29-2014, 07:47 PM   #25
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Here's a link to where a guy talked about it, light on needing a regen, highway trip let it regen and self cleared the code.

2013 2500 Longhorn 23 Hrs. of Idle results. - Dodge Cummins Diesel Forum
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Old 04-29-2014, 08:03 PM   #26
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Gasoline has vapors which can be ignited by a spark, and cause a fire. This is why you should always shut down a gasoline engine when refueling, as tons of vapors are released during this process, and sometimes the outside air movement isn't enough to get vapors away from the vehicle. Diesel does not emit vapors like gasoline, and does not explode like gasoline, therefore does not have the same issues as gasoline.

Not sure about the duramax, but the Cummins on my truck has the automatic high idle feature which monitors exhaust temps and other factors of the SCR system. If they are not running optimally, the system will put the engine into automatic high idle. I can also set high idle manually, which I do when I notice it in regen and I'm about to shut the truck down. While you shouldn't let the truck idle for too long, idling when you're working the crap out of the engine shouldn't be a big deal in the long run. You're going to get right back on the freeway and get everything super hot again.
This does not explain why it is necessary to shut down the engine. Yes gas vapors are highly explosive, but you still have to have an IGNITOR!! Where is the ignitor when the engine is running?? static electricity is the leading cause of gas tank fill fires, but I guarantee you there is not more static electricity in a running car than there is in one that's shut off. The static comes from the human getting in & out of their vehicle. You have failed to disprove my point that leaving your gas engine running during refueling is no more dangerous than fueling while it's off. In my 25+ years of fueling my vehicles, I rarely turn off my engine, & I have never had anything happen. I also make sure I touch the side of my vehicle before I go back to the fuel door to discharge any static electricity. (which has no difference running or not).
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Old 04-29-2014, 08:17 PM   #27
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I never turn of my diesels when fueling, or making quick stops, or durring longer stops in the winter.
50% of the time I turn off the gassers when fueling, but if its cold, I usually leave it on too.
I usually fill up about 3 times a week, no issues so far!

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Old 04-29-2014, 08:24 PM   #28
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I don't shut down to fuel, after pulling 19,000lbs for 2-3 hours it's not just EGT's I worry about, the trans. fluid is hot, it won't cool down with the easy run up the ramp and to the pump, if anything it gets hotter as the TCC is no longer locked up and is now slipping and building heat, every thing under the hood is hot, keeping fluids moving is always the best thing if you only stop for 10-15 minutes, less harm in that than shutting it down.
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Old 04-29-2014, 08:37 PM   #29
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False. Common rail systems idle at 6,000PSI plus. No worry about fueling issues there, next time you run across someone with a scan tool that has bi-directional control ask them to test the fuel pressure, a Duramax can make 21,000PSI+ at idle. If working properly, those concerns went out years ago, even mechanically injected diesels don't have that issue unless you've got injector problems.



That's why I asked for links, what you said runs counter to an awful lot of GM training I went through.



I'm not advocating never shutting down or leaving it idle during dinner, but you're not going to ruin your DPF or wash down your cylinders either.


I don't need to ask for a scan tool as I am fortunate enough to have many gauges installed on my rig. I can verify you are correct that my common rail actually idles at 7,000 psi.

There is a big difference in 7,000 to 21,000 psi, 300% as a matter of fact. I don't believe the spray pattern would be the same at varying pressures. Simple physics tells you that in a pressure vs orifice spray pattern that pressure changes change the spray pattern.

I cannot verify or prove my beliefs on this matter but I am going off of my own real world experience as far as fuel flow is concerned.

I'd be curious to see a 21,000 psi duramax at idle though if you don't mind, that would be interesting. Also not sure what the benefit of that would be. Ideas?
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Old 04-29-2014, 08:46 PM   #30
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21,000psi at idle it will knock like hell!
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