Diesel Engine Idling

[Bandit1047]

Whenever I see a truck or a backhoe idling for hours at a time, it drives me nuts. (My wife says it's no drive, just a short putt!) When you ask people why they are idling their equipment, you get the most outrages answers; "diesels don't start when they are hot", "It hurts the engine starting it". These are just two of many answers I get when I ask the question. Neither of these is true, in fact all four major American engine manufacturers discourage engine idling. Cummins told me that engines that are subjected to long periods of idling need approximatly 30% more maintenance. Diesel engines need RPM or load to run at correct operating temperatures. On some equipment you can watch the temp. gauge drop as the engine sits idling. Cool diesels do not burn all the fuel that is injected into the cylinders, this causes carbon deposits on the valves and pistons and fuel to leak past the piston rings and as it runs down the cylinder walls takes the carbon with it glazing the cylinder walls. This carbon makes your oil gritty (black) and the sulfer in the fuel mixes with any condensation turning it into sulfuric acid. Non of this is good for the engine. The carbon build up on the valves and pistons reduces your fuel efficency. An idling diesel engine can burn 1/2 to just over a gallon of fuel per hour, and if your injectors are bad, it can reach 2 gallons an hour. At a cost of over $4.00 per gallon, who in their right mind still idles their diesel?

 

[Tazza]

I never thought much of the fuel consumption. Mainly the un-burnt fuel issues.
I have been told that idling any engine for extended times is not good, diesels are worse because they carbon up. They also need to be under load to burn clean.
Gotta love the one that they don't like starting hot, thats when a diesel is the happiest!

 

[Land-Tech]

I never thought much of the fuel consumption. Mainly the un-burnt fuel issues.
I have been told that idling any engine for extended times is not good, diesels are worse because they carbon up. They also need to be under load to burn clean.
Gotta love the one that they don't like starting hot, thats when a diesel is the happiest!

A lot of the diesels that come off the the slope and are sold for auction seem to have problems with piston slap where the piston skirts have excessive wear from long idling periods. Myth?
A friend bought a 98 chevy 1-ton and had to replace the motor and the mechanic said the engine don't get enough lube when they idle. I guess not enough oil splash on the lower cylinders.
I do more idling in the winter than I want to but things have to stay warm including me.And fuel cosumption is getting to be a real issue so I try and shut things off as I rotate between machines.This factor alone will curtail most idling scoflaws if they have to pay for there own fuel. Scott

 

[Earthwerks Unlimited]

A lot of the diesels that come off the the slope and are sold for auction seem to have problems with piston slap where the piston skirts have excessive wear from long idling periods. Myth?
A friend bought a 98 chevy 1-ton and had to replace the motor and the mechanic said the engine don't get enough lube when they idle. I guess not enough oil splash on the lower cylinders.
I do more idling in the winter than I want to but things have to stay warm including me.And fuel cosumption is getting to be a real issue so I try and shut things off as I rotate between machines.This factor alone will curtail most idling scoflaws if they have to pay for there own fuel. Scott

Diesel idling, from my experience living near Detroit where engines in the winter used to run through the night comes from OTR trucks. I asked my trucker neighbor why he did that and his explanation was that starters were very costly, and fuel wasn't. I'm not so much concerned about idling and the mechanical aspects as I am about other affects; it's the running up of the hour meter. Look at it this way---let it idle 5 minutes per day for a normal working year--say 300 days that's a whopping 1500 minutes or 25 hours. Multiply that times how many years of normal ownership before trade-in---say 5 years, and that's 125 hours of deductible, costly hours at trade-in time.

 

[Bandit1047]

Diesel idling, from my experience living near Detroit where engines in the winter used to run through the night comes from OTR trucks. I asked my trucker neighbor why he did that and his explanation was that starters were very costly, and fuel wasn't. I'm not so much concerned about idling and the mechanical aspects as I am about other affects; it's the running up of the hour meter. Look at it this way---let it idle 5 minutes per day for a normal working year--say 300 days that's a whopping 1500 minutes or 25 hours. Multiply that times how many years of normal ownership before trade-in---say 5 years, and that's 125 hours of deductible, costly hours at trade-in time.

Since I started this thread I should also give a history on diesel Idling. This is what I was told by an old diesel Mechanic who worked on them since he was a kid. The old diesel behemoth engines in off road equipment needed a gas pony engine to start them. Back in those days diesel was 5 to 8 cents a gallon and shutting them down was a pain because the pony engine being gas was less likely to start than the diesel. These old diesels could also be difficult to start. This old man told me he has heard 200 reasons for idling a diesel and only two come close to being true. One is that if you have an air leak in your fuel system, (rubber fuel lines develop pin hole leaks that will not leak fuel but will bleed air allowing the fuel to flow back to the tank.) This causes long crancking time to start. Thats my story and I am sticking to it. Joe

 

[Orgnoi1]

Since I started this thread I should also give a history on diesel Idling. This is what I was told by an old diesel Mechanic who worked on them since he was a kid. The old diesel behemoth engines in off road equipment needed a gas pony engine to start them. Back in those days diesel was 5 to 8 cents a gallon and shutting them down was a pain because the pony engine being gas was less likely to start than the diesel. These old diesels could also be difficult to start. This old man told me he has heard 200 reasons for idling a diesel and only two come close to being true. One is that if you have an air leak in your fuel system, (rubber fuel lines develop pin hole leaks that will not leak fuel but will bleed air allowing the fuel to flow back to the tank.) This causes long crancking time to start. Thats my story and I am sticking to it. Joe

*most* locomotives idle all winter on and off... they are never shut down... just food for thought...

 

[OldMachinist]

*most* locomotives idle all winter on and off... they are never shut down... just food for thought...

Check out this link for just about every thing you want to know about the legality of diesel idling.
http://on.dot.wi.gov/wisdotresearch/database/tsrs/tsrdieselidling.pdf
And here for a list of laws by state.
http://www.scribd.com/doc/2170989/2008-Idle-Laws-by-State
Some states like Ma. even restrict the idling of locomotives to 30 mins.

 

[Tazza]

Check out this link for just about every thing you want to know about the legality of diesel idling.
http://on.dot.wi.gov/wisdotresearch/database/tsrs/tsrdieselidling.pdf
And here for a list of laws by state.
http://www.scribd.com/doc/2170989/2008-Idle-Laws-by-State
Some states like Ma. even restrict the idling of locomotives to 30 mins.

I can understand it in cold areas, especially large engines. You need to crank it and get it warm enough to fire so when its sub zero temperatures. I alwats heard it glazez the bores up and carbons the head and valves. You need the engine to have a set load on it at all times or it doesn't burn cleanly.
Thankfully where i live, starting a diesel isn't an issue, just a short glow then it will fire easily. I don't need block heaters or to tarp it and use a heater.

 

[Jyuma]

I can understand it in cold areas, especially large engines. You need to crank it and get it warm enough to fire so when its sub zero temperatures. I alwats heard it glazez the bores up and carbons the head and valves. You need the engine to have a set load on it at all times or it doesn't burn cleanly.
Thankfully where i live, starting a diesel isn't an issue, just a short glow then it will fire easily. I don't need block heaters or to tarp it and use a heater.

I power washed the engine compartment of my Thomas T133 the other day and in order to speed-up the drying process I left the engine idling for quite some time. After it dried and I hit the throttle to move the machine, a large cloud of blue(ish) smoke billowed from the exhaust. It quickly dissipated but is that what you folks are talking about when you say long periods of idling causes build-up of ugly stuff?

 

[Tazza]

I power washed the engine compartment of my Thomas T133 the other day and in order to speed-up the drying process I left the engine idling for quite some time. After it dried and I hit the throttle to move the machine, a large cloud of blue(ish) smoke billowed from the exhaust. It quickly dissipated but is that what you folks are talking about when you say long periods of idling causes build-up of ugly stuff?

When a diesel is running without load or not much load the fuel does not fully burn. This is what you noticed when you throttled up to drive away. It can also (apparently) glaze the bores causing low compression.
I don't know just how much idling you need to do to cause issues, or if in a real life situation it actaully happens, or is just a rare thing that happens from time to time. I try to not idle my machines for any extended periods of time, be them Diesel or Petrol.

 

[RodNH]

When a diesel is running without load or not much load the fuel does not fully burn. This is what you noticed when you throttled up to drive away. It can also (apparently) glaze the bores causing low compression.
I don't know just how much idling you need to do to cause issues, or if in a real life situation it actaully happens, or is just a rare thing that happens from time to time. I try to not idle my machines for any extended periods of time, be them Diesel or Petrol.

I have a Bobcat S650. The low idle is 1330 rpm. That seems high to me but the spec for low idle is 1250-1450 rpm. However, this is my first skid steer so I have no background experience. When I use the skid with my snowblower, I run it WOT in high flow. WOT high idle by spec is 2525-2650 rpm. That's fine for my snowblower but causes an issue for me when using my backhoe. Since my lowest idle speed is about half my maximum, standard flow is still quite a lot. Standard flow at minimum idle (1330) results in about 11-12 gpm. The backhoe manual recommends flow to be 11-14 gpm. That may be fine for an experienced operator but it's pretty fast for me as a newbie. I therefore do not run the skid above low idle when using the backhoe and try to feather the BH controls as best I can. My work is only for myself on my own property and is intermittent with no more than a couple hours at a time. It may add up to a significant amount over a year. It is also predominantly at no/light load.
I don't know why the fast (to me) idle speed. It may have something to do with current emissions requirements. The skid meets Interim Tier IV standards. It's about 8 months old.
Should I be concerned with idling as noted above? I am considering adding a priority flow divider to cut the flow to the BH without running the skid on relief. If I really should be running with more throttle, it might effect my selection of a flow divider. Thoughts?

 

[Tazza]

I have a Bobcat S650. The low idle is 1330 rpm. That seems high to me but the spec for low idle is 1250-1450 rpm. However, this is my first skid steer so I have no background experience. When I use the skid with my snowblower, I run it WOT in high flow. WOT high idle by spec is 2525-2650 rpm. That's fine for my snowblower but causes an issue for me when using my backhoe. Since my lowest idle speed is about half my maximum, standard flow is still quite a lot. Standard flow at minimum idle (1330) results in about 11-12 gpm. The backhoe manual recommends flow to be 11-14 gpm. That may be fine for an experienced operator but it's pretty fast for me as a newbie. I therefore do not run the skid above low idle when using the backhoe and try to feather the BH controls as best I can. My work is only for myself on my own property and is intermittent with no more than a couple hours at a time. It may add up to a significant amount over a year. It is also predominantly at no/light load.
I don't know why the fast (to me) idle speed. It may have something to do with current emissions requirements. The skid meets Interim Tier IV standards. It's about 8 months old.
Should I be concerned with idling as noted above? I am considering adding a priority flow divider to cut the flow to the BH without running the skid on relief. If I really should be running with more throttle, it might effect my selection of a flow divider. Thoughts?

I wouldn't be worried. From what i understand, the biggest issue with idling is the fact there is little to no load on the engine. When you are using your backhoe attachment you will be loading the engine, so it shouldn't build up carbon like they say can happen when there isn't enough load. Like i said, this is only from what people tell me, i don't know if its really true or not, or if it is, when you start working it, it could simply burn off.
When i use my backhoe, i run half or less throttle, no sense running it flat out using more fuel when i don't need the extra oil flow.

 

[hydrostatic]

I have a Bobcat S650. The low idle is 1330 rpm. That seems high to me but the spec for low idle is 1250-1450 rpm. However, this is my first skid steer so I have no background experience. When I use the skid with my snowblower, I run it WOT in high flow. WOT high idle by spec is 2525-2650 rpm. That's fine for my snowblower but causes an issue for me when using my backhoe. Since my lowest idle speed is about half my maximum, standard flow is still quite a lot. Standard flow at minimum idle (1330) results in about 11-12 gpm. The backhoe manual recommends flow to be 11-14 gpm. That may be fine for an experienced operator but it's pretty fast for me as a newbie. I therefore do not run the skid above low idle when using the backhoe and try to feather the BH controls as best I can. My work is only for myself on my own property and is intermittent with no more than a couple hours at a time. It may add up to a significant amount over a year. It is also predominantly at no/light load.
I don't know why the fast (to me) idle speed. It may have something to do with current emissions requirements. The skid meets Interim Tier IV standards. It's about 8 months old.
Should I be concerned with idling as noted above? I am considering adding a priority flow divider to cut the flow to the BH without running the skid on relief. If I really should be running with more throttle, it might effect my selection of a flow divider. Thoughts?

the onspoke reason for the high idle is that bobcat has a high load on idle let say for instance 900 rpm and the machine wil smoke black exhaust (tier 4/5 my ass) because of big pumps in your case somtimes 5 in a row big discusions over here but kubota can not assist about your backhoe if you run deluxe panel and new backhoe with controler its posible to select backhoe and the machine will automaticly adjust the flow talk to dealer about that if not Seen once that the owner has put mechanicly end stops on de valve blok to limit the aux travel flow when acuated greet h

 

[biggie]

Any diesel enginge. Work the P&SS out of it. Idling will kill it. But high idle helps to not do damage it.If that's not an option. Block heaters/Engine Heaters. I plug my machine in at night. I live in Canada,-40c. 0-40 oil year around,+40 in the summer. Not a problem. You can get remote engine heaters installed[wabasto] There's more out there.

 

[South Texas Rancher]

One reason I let my machines idle is to help prolong turbo charger life. All most every machine I own has a turbo. Turbos get really hot. What happens if you just turn the engine off every time you stop. Do that a lot and you can cook a turbo. I like the idea of letting the engine run at least five minutes to keep the oil flowing and help cool the turbo and engine down. If you are doing a lot of stopping and starting during your work day that is a lot of wear tear. I think you are better of a least letting it run long enough to cool down. Where you live and time of years makes big difference. I live on the Texas coast, 100% humidity and over 100s day of 100 degree temps will stress an engine. Works for me.

 

[Tazza]

One reason I let my machines idle is to help prolong turbo charger life. All most every machine I own has a turbo. Turbos get really hot. What happens if you just turn the engine off every time you stop. Do that a lot and you can cook a turbo. I like the idea of letting the engine run at least five minutes to keep the oil flowing and help cool the turbo and engine down. If you are doing a lot of stopping and starting during your work day that is a lot of wear tear. I think you are better of a least letting it run long enough to cool down. Where you live and time of years makes big difference. I live on the Texas coast, 100% humidity and over 100s day of 100 degree temps will stress an engine. Works for me.

I totally agree on letting the turbo cool down after a good flogging. Keeps the oil flowing to the bearings and helps prevent it turning to carbon.

 

[Mikefromcny]

I totally agree on letting the turbo cool down after a good flogging. Keeps the oil flowing to the bearings and helps prevent it turning to carbon.

What about when its cold out, like below freezing? I let my machines idle for 5-10 mins before using and gradually increase throttle. They do sit outside though. to me not much sounds worse the revving up a cold diesel. In the summer, temps between 60F-90F, I'll start it and start using it while gradually increasing throttle. I always let them idle for a minute or 2 prior to shutting them off for cool down.

 

[Tazza]

What about when its cold out, like below freezing? I let my machines idle for 5-10 mins before using and gradually increase throttle. They do sit outside though. to me not much sounds worse the revving up a cold diesel. In the summer, temps between 60F-90F, I'll start it and start using it while gradually increasing throttle. I always let them idle for a minute or 2 prior to shutting them off for cool down.

I see no issue with that, they are just concerned with idling for hours on end.

 

[Kanman]

I see no issue with that, they are just concerned with idling for hours on end.

Although much idling is a pure waste of fuel. It's not doing as much harm as some of these posts would lead you to believe. Diesel engines no longer "wash down/wet stacking" the cylinders like they used to. Most engines these days have an ECM controlling pulse width, timing and sensors. Where as the older pump controlled motors had no such advantage. One thing is for sure. Every time a crankshaft goes around, that's 1 less time it will ever do so.