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  #1  
Old 01-28-2016, 11:10 PM
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Leave it running or turn it off.

i have noticed that big trucks often leave diesels running and don't turn them off. I have been leaving mine running a lot when I go shopping or stop at the bank. Since I have to turn off key, reach under dash, find brown vac lines pull chopstick out of one, then connect it to line that shuts off fuel. Then unconnect brown line and reinstall chopstick plug. It's even more fun in the dark! Anyone else do this? Am I harming my beloved 83 300d turbo? I'd feel better if it removed the key, but then wouldn't the glow plugs turn on again when I reinserted the key? Is that a bad thing? Mike

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Old 01-28-2016, 11:17 PM
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Quote:
Originally Posted by 123mike View Post
i have noticed that big trucks often leave diesels running and don't turn them off. I have been leaving mine running a lot when I go shopping or stop at the bank. Since I have to turn off key, reach under dash, find brown vac lines pull chopstick out of one, then connect it to line that shuts off fuel. Then unconnect brown line and reinstall chopstick plug. It's even more fun in the dark! Anyone else do this? Am I harming my beloved 83 300d turbo? I'd feel better if it removed the key, but then wouldn't the glow plugs turn on again when I reinserted the key? Is that a bad thing? Mike
Wouldn't it be easier to fix your vacuum lines so that you can just turn the car off with the key?

Externally, you're putting more stress on every vibration-absorbing component surrounding your engine (think motor mounts, air cleaner bracket, etc). Internally, you're creating much more soot at idle, ultimately contributing to oil and engine wear. That isn't to say you'll have issues, but from a theoretical perspective it's not great for your engine.
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  #3  
Old 01-28-2016, 11:58 PM
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Big rigs often have idle controllers to keep it up enough to prevent "wetstacking," something that can occur when combustion temps fall too low, as they do with extended idling at normal Benz diesel idle speeds.
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Old 01-29-2016, 12:08 AM
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I read changing out ignition switch to fix pneumatic off switch is not easy. Let me know if it is doable to just change pneumatic part. I will stop idling . I had in my mind that turning diesels off and on was worse than leaving them idling for 10 minutes.
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  #5  
Old 01-29-2016, 05:53 AM
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Its not a big deal either way. Idling is not good for the engine and is very mildly harmful. I leave them running a lot when its very cold out...on occasion overnight or all day if its 15 below. I take an extra key and lock the doors.
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  #6  
Old 01-29-2016, 06:33 AM
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The vacuum valve on the ignition is two screws. Tough to access, but way easier if you pull the cluster out and under dash panel out.

The valve is simple, unlikely it is the problem but possible. X2 fix the system so you dont have to do that nonsense under the dash. Sounds like a PITA as well as a waste of fuel. Nothing will be harmed including the glow plugs by returning things to normal operation. You can always skip the glow cycle anyway and just start the car if the engine is hot.

Big rigs are technically not supposed to idle in place for emissions reasons, many are fitted with an auto shutoff after a certain period of time.
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  #7  
Old 01-29-2016, 07:07 AM
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Your shut off controller (actuator) may be suspect.

Remove the brown/violet vac line going to it, is there any evidence of oil? If so, you have a ruptured diaphragm, replace it.
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  #8  
Old 01-29-2016, 09:02 AM
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"Big rigs" have direct injection engines, very different from our MB diesels with indirect injection. They don't suffer from carbon build-up like your engine. Carbon in your engine = increased wear and decreased fuel economy. I consider leaving a car running over night to be an emergency measure, and not something to do routinely.

Fix the problem. While waiting for parts and time/tools to do the job, in your shoes I would extend the vacuum line from under the dash so that I could easily use the suction of my mouth to shut off the car, or rig up a squeeze bulb or mity-vac.
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  #9  
Old 01-29-2016, 09:12 AM
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It depends how well you maintain your engine. Are the valves adjusted to spec, fresh oil, new oil filters, diesel purge run through, valve stem seals, carbon build up in and around glow plugs, etc if your on top of all that then don't fret if its a reasonable amount of time. Keep up on the maintenance and you'll be good.
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  #10  
Old 01-29-2016, 11:45 AM
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Quote:
Originally Posted by 123mike View Post
i have noticed that big trucks often leave diesels running and don't turn them off. I have been leaving mine running a lot when I go shopping or stop at the bank. Since I have to turn off key, reach under dash, find brown vac lines pull chopstick out of one, then connect it to line that shuts off fuel. Then unconnect brown line and reinstall chopstick plug. It's even more fun in the dark! Anyone else do this? Am I harming my beloved 83 300d turbo? I'd feel better if it removed the key, but then wouldn't the glow plugs turn on again when I reinserted the key? Is that a bad thing? Mike
This is what I was told in Diesel Mechanics Tradeschool. When Big Rig Trucks move they are generally loaded. When the pull off of the Freeway and stop at lets say a Truck Stop to eat if they shutoff the Engine (remember the Engine was pulling at a considerable load) the heat spikes and the Oil runs off of the Parts leaving the engine dry for the next start.
So lubrication is one of the reasons they leave it running.

The other reason is that if they Engine was shut off when they came backe from eating they would have to warm up again because it is a bad idea to jump in and drive off and go to full load with a cold Engine.
Winter Weather makes that worse.

The last part is less obvious. As it has to do with Heat transfer to other parts. The Engine and Transmission and so on get hot at different rates. So if the Engine is hotter than the trans so for a while there is heat coming off of the Engine and transfering to the trans or which ever is cooler. Eventually that stabalizes.
Leaving the Engne running helps to keep everything stabalized heat wise.

In the Case of a Car you seldom operate at full load especially if you were going shopping to several places and in stop and go traffice everthing that could absorb heat has a lot of time to dump off the heat so that if you park in a parking lot to shop while the Oil does drain off the parts the heat spike is not any where near what is on a big Rig pulling off of the Freeway and stopping.

If if you did get into the Car with the Engine Cold and take off right away you are no likely to be fully loaded.

I know people will not agree with this but that is what I was told.

I was also told that it was Detroit Diesels that in Winter Weather can get too cold while idling because when the Exhaust Valves (the only valves it has) are open the Blower is blowing a large volume of Air through the Cylinder Ports and out of the Valves. That volume of Air is a larger volume than a Cylinder full of Cold Air that a 4 Cycle engine would. Any way the effect is that at idle the cold Air during Winter cold can sometimes over cool the Cylinders.

Delivery Trucks often leave the Engine running to keep from wearing out the Starter. Picture how many times a UPS of FedEx Driver would start an Engine if they did that at every stop they made.
And, they also have that hot Oil draining off of the Parts issue to add to that.
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Last edited by Diesel911; 01-29-2016 at 12:00 PM.
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  #11  
Old 01-29-2016, 12:26 PM
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Originally Posted by Diesel911 View Post
In the Case of a Car you seldom operate at full load <>
Have you ever driven a 240D automatic? (LOL)
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Old 01-29-2016, 12:29 PM
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Originally Posted by Diesel911 View Post
I was also told that it was Detroit Diesels that in Winter Weather can get too cold while idling because when the Exhaust Valves (the only valves it has) are open the Blower is blowing a large volume of Air through the Cylinder Ports and out of the Valves. That volume of Air is a larger volume than a Cylinder full of Cold Air that a 4 Cycle engine would. Any way the effect is that at idle the cold Air during Winter cold can sometimes over cool the Cylinders.
That and the fact that even a fresh DD 71-series or 92-series will only start below ~45F with a block heater or ether, ... if you can't plug it in you leave it running!
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  #13  
Old 01-29-2016, 02:33 PM
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I had to leave one of my 240ds running as I was stranded overnight in cold snowy weather. It kind of surprised me that the engine was able to maintain good temperature using so little fuel over the seven to eight hours. It was still warm and toasty the next morning.

I was certain there where no exhaust leaks and a wind was blowing. So I left the window down a crack and slept. I was very tired from fighting the storm and icy hilltops for many hours. I had just pushed it too far to reach a motel that night. Next morning when I woke the plows and salt truck had done their thing.

In retrospect it may have been better to increase the manual idle speed control but I did not think of it.

I have owned a shorter stroke 9 liter V8 diesel and the dealership told me not to let that engine idle for long periods. Or lug it. That particular engine does not like it.

I did not check but these old engines are probably not short stroke engines.
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Old 01-29-2016, 02:45 PM
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When I swapped in a 617 to my 107, I had to design a shutoff since the ignition switch didn't have the vacuum shutdown valve. I used a vacuum switchover valve and a momentary push button switch for shutdown. This also allows me to remove the key and lock the car with the engine running if desired. It's rarely needed, but nice option to have.

It's the perfect companion to the manual glow plug switch.
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  #15  
Old 01-29-2016, 02:55 PM
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Check your state laws...

SC Code of Laws

SECTION 56-5-2570. Parking of unattended motor vehicle.

No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, locking the ignition, removing the key and effectively setting the brake thereon and, when standing upon any grade, turning the front wheels to the curb or side of the highway.

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