letting a diesel run??

[Ryan_V]

Now that I have one, I notice lots of guys leave their diesels run while they run into the store... etc for a short period of time. What is the purpose? How long is the cut off as to when you leave it run vs. shut it off and restart???

[croixflats]

I was always in the frame of mind that a diesel is very efficient when ideling so why shut it off, plus diesels sound way cool.

I know on hot days like today I would be running one non stop at the job site to have cool place to chill out.

The efficiancy aspect may be an old wise tale and it just maybe a bit of "look I have a diesel" thing which is all fine and good in my book.

[jeffreyd]

There are several schools of thought. The one biggest thing is that after you are driving the turbo is spooled up. It is cooled by oil that pours onto the bearing and shaft. If you simply pull in and shut down, it does not give the turbo time to spool down and by shutting the engine off you stop all oil flow to the bearing/shaft. So if a person does this type of shut down on a regular basis, it will allow for premature failure of the turbo.

The operators manual usually states that the engine should idle 3-5 minutes before shutdown. Today with the cost of fuel, the emissions issues, and other items people dont do the cool down time.

By idling it also allows the exhaust temps to come down to a lower temp. One newer vehicles that use particulate filters and other methods to control hydrocarbons in the exhaust, which is now almost cleaner than the air going into the engine, it is imperative to let them idle. The exhaust temps because of the systems that burn off the HC can go up ward of 1200 degrees.

Sorry to be long winded, a lot goes into diesel technology these days.

[Ryan_V]

long winded is good!!! Thanks!! I like to somewhat understand things I have, and a diesel is brand new to me. I like to read and research alot, so get as long winded as you want!!! Plus, my truck came from your state So, I should let it idle for 5 minutes or so when we get to the campground tomorrow with the camper....

[BobT]

I agree with Jefferyd. If your diesel is turbo charged I'd take his advice and cool your engine down a couple minutes before shutting down. Check your owner's manual if you have it and see what they recommend.

I always cool down an engine, even gasoline, for a few minutes if I've been driving it rather hard like down the highway.

One thing to keep in mind about idling a diesel. Old school thinking has been that it is good to idle them but this is not true for extended periods. My tractor manuals and my truck manual advise against idling for more than 10 minutes at a time unless you can bring the idle up while idling the engine. It is my understanding that most truckers have a way to set their idle up when they leave them idling for sleeping. Idling too low can cause build-up of carbon and soot.

[311Hemi]

One thing to keep in mind about idling a diesel. Old school thinking has been that it is good to idle them but this is not true for extended periods. My tractor manuals and my truck manual advise against idling for more than 10 minutes at a time unless you can bring the idle up while idling the engine. It is my understanding that most truckers have a way to set their idle up when they leave them idling for sleeping. Idling too low can cause build-up of carbon and soot.

[deadeye]

There are several schools of thought. The one biggest thing is that after you are driving the turbo is spooled up. It is cooled by oil that pours onto the bearing and shaft. If you simply pull in and shut down, it does not give the turbo time to spool down and by shutting the engine off you stop all oil flow to the bearing/shaft. So if a person does this type of shut down on a regular basis, it will allow for premature failure of the turbo.

The operators manual usually states that the engine should idle 3-5 minutes before shutdown. Today with the cost of fuel, the emissions issues, and other items people dont do the cool down time.

By idling it also allows the exhaust temps to come down to a lower temp. One newer vehicles that use particulate filters and other methods to control hydrocarbons in the exhaust, which is now almost cleaner than the air going into the engine, it is imperative to let them idle. The exhaust temps because of the systems that burn off the HC can go up ward of 1200 degrees.

Sorry to be long winded, a lot goes into diesel technology these days.

All of this+++

Its called oil coking and its a major pita for turbos in general. I have a turbo timer on my Talon (obviously not a diesel but it has a big turbo just the same) for just this reason. Some people will claim its not that big of a deal but after having taken apart a few turbos in my time I will argue otherwise. If you pop your hood at night after making a long/hard haul you will see that the turbo is red hot. If you give it a little time to let coolant and oil circulate it does cool down a lot.

Now I am pretty sure they got a no idle law on the books now but I'm willing to argue with a officer since a ticket is cheaper than a turbo.

[jeffreyd]

you can purchase a kicker that will bring the idle up, it plugs into the computer. The one thing is i would let it idle for 5 min if you are pulling a load somewhere. The issue comes in as to what has been done in the past. as i noted in a post sometime ago, we use to use the block heaters year round on all of our fire trucks including the smaller diesels. the newer trucks would cycle on and off depending on the ambient temp but when you are in mn and the temp is dipping in the winter i would always plug it in. you should not notice any difference between the az and mn operations as both are considered extreme in my eyes. one thing i would do is find out the last time the differentials were serviced. Dodge says every 15k on their synthetic lube. I would convert it to amsoil or something that you can run longer. same with the transfer case if it 4x4.

I agree with the post above that if you want to use the PTO function you can have it flashed. But one thing you should think of is that most semi drivers now do not use high idle when sitting as the newer trucks have a small diesel driven generator to cut down on the emission release. The APU on those trucks will power the a/c and tv etc while they sleep. Also if you go by some of the truck stops they have air handler systems installed where the driver can pull in put a suction hose on the exhaust and it will scrub the air while they idle.

Ever seen a JB hunt truck sitting along the road? Many times the engine will shut down if they meet the driving hours set in the computer. they cant restart until the computer resets the hours. Also no more idle time for a lot of the trucking companies.

Also if you have to replace batteries, do both of them at the same time. I would look and see the last time they were replaced as here in az if you get 18 months out of a battery you are in tall cotton. I average about 14 months on both of mine and I do not drive much.

Good luck enjoy your truck.

Jeff

[311Hemi]

Also if you have to replace batteries, do both of them at the same time. I would look and see the last time they were replaced as here in az if you get 18 months out of a battery you are in tall cotton. I average about 14 months on both of mine and I do not drive much.

Good luck enjoy your truck.

Jeff

I still have the original batteries in my 03', and still going strong.

The heat really affect them that much down there? Seems odd that you average a little over a year on batteries, but can't say I have lived down south.

[croixflats]

Very cool and informative info. I'm just an old school diesel guy that has not been around the new so this is neato. Many fond memories as kid riding in the semi with dad.

Pardon the neato,

[BobT]

As far as changing batteries go the question of whether to replace both or just one may depend in part on the design. If your batteries are connected in series to provide 24v to the starter, the only reason you would have for changing both is if both are bad and need to be changed. On the other hand, if they are connected in parallel (this is very typical for pickups) then if one goes bad, there is a good chance it will damage the other one and force you to replace both.

In either scenario, it is best to load test the batteries to make sure your starter is getting the power it needs.

[broken_line]

thats the main reason i leave our tractors idle after working them hard, the turbo gets HOT and when you remove the oil supply sometimes it will burn all the oil off the shaft and the next time you start it, it is dry.. do that for a few years.. and you will have a screaming mimmi turbo (: then it will make some noises that any man will cringe at (:

[jeffreyd]

Yes actually many folks that do their own maintenance will preventively change them at a year to 18 months. My 04 dodge ram is on its 3 rd battery. In the fire trucks we converted everything to "6 packs" 3 batteries on each side of the frame tied together for 12volts. When one battery goes bad the whole 6 pack gets changed. What we have found and doing studies with Neihoff mfg, that when one battery fails, it robs the others of power from the alternator. Over time, if you simply replace the one that is bad, soon after you would have another go south. By the time you figure downtime and labor to change individual batteries because you have to separate all the pack every-time, you could have replaced the battery.

The ambient temp kills them quickly, one reason the chargers and draw is always going on in the truck.

On my personal cars, i do my own pm's and load test my batteries periodically. You have to figure the temp under the hood can reach 200 degrees in the summer. That is why we see police cars with the hoods open to help scrub off some of the heat from the pavement. I wish i could get more than a year or so out of batteries. The best ones that we found out of our testing was is suggested by NFPA for all fire fighting equipment is the Delco 1150 or 1151 battery. It will take the quick discharge, deep cycling, then charging and constant loads that are on the system.

Hope that helps, nothing is worse than having a battery explode under the hood. have seen it many times.

[jeffreyd]

Hey Bob, most automotive trucks 1 ton and under are 12 volt start 12 volt run. Occasionally we will run into a 24v start 12 volt run. Actually buddy of mine called me last week that he was working on this type. MFG do some crazy things, granted spinning the engine at 24 volt start will pull less amps, it is not like you are doing it all the time. Heck CF trucking runs air starters on their rigs. Nothing worse to blow an air line, drain the system, then cant start the engine. It wont be long before we see 36 volt and 48 volt systems. Recently the hot talk is going to a 96 volt system but hopefully that will be long away, it will wipe out the little guys as the equipment and training to work on them is going to be extensive.

Certified EVT, ASE, NFPA emergency vehicle mechanic. I am also on the certification commission F-4 low voltage testing committee for emergency vehicle mechanics. We write and certify each test that is given in order to be compliant with NFPA 1071.