Poll: How long will you let your diesel idle? - PeachParts Mercedes-Benz Forum

diesel don · #1 01-12-2004, 11:18 AM

This topic fascinates me because of the huge stress of cold weather starting. To me these cars love to run but hate to start. Therefore I've been intrigued by:

1. Truckers whose rigs are either at idle or running full open for weeks on end.
2. Diesel locomotives which swap oil while running (never shut down)

Last week was cold here. Single digits during the day. My TD is idling on average of about 15 hours per tank. I still get around 19 mpg.

Twice now I've allowed it to idle for 12 hours at a time.

Don

Lars · #2 01-12-2004, 12:07 PM

It's been in the -20's F around Montreal. I'll leave the TD idleing for an hour or two during the day just to prevent it from becoming too cold. If I do that, car starts like if it was 30F outside. It would not start at the end of my work day otherwise.

lietuviai · #3 01-12-2004, 12:26 PM

Right now with the temps in the upper 20's to low 30's I only let idle for about a minute if even that long. I just go when I feel the car won't stall.

Ken300D · #4 01-12-2004, 01:04 PM

I think he's talking about overnight idling to keep it warm and runnable.

If I did that at work in the parking garage they'd call the fire department because of the smoke. But in planning ahead for really cold weather, I've noticed that a few parking spaces have power outlets on the wall in front of them. So the block heater is my plan.

Been thinking about an all-electric car, but don't think I can get enough current from an outlet to charge it enough to go home.

Ken300D

acastell · #5 01-12-2004, 01:24 PM

12 hours straight? Am I to understand that you let the car sit for 12 hours with the engine running.

I am new to diesels...this seems like a long time. I have read a few old posts discussing owners tendancies to let a car idle while they run into a store for a minute, but 12 hours, wheeeew!

I live in Ca, so the temps never get too cold. I do however, let the car run if I am running into a market to pick up an item or two. Total idle time is probaly 5 min.

Even at 5 min, I felt this could be bad for the car, obviously not!

I learn someting new everyday...

AC

psfred · #6 01-12-2004, 01:59 PM

Much less wear and tear on the engine leaving it idling than by shutting it off and letting it get cold, then restarting.

I leave mine idling when I'm just stopping for a couple minutes if the engine is cold. Warm I don't bother.

I've not yet left it idling all night, but if it gets down to -10 F I probably will just so I can drive it in the morning.

Newer diesles will get below normal operating temps on extended idling -- they will also never reach operating temp until you drive them. I remember sitting at the railroad crossing down the hill watching the temp gauge go down last winter while waiting for a slow train. Nippy in the car!

Fuel consumption at idle for a diesel is very small, so you won't use all that much just letting it idle.

Peter

jhahn · #7 01-12-2004, 02:17 PM

I don't know about the MB diesel, but Cummins doesn't recommend idling the 5.9 or 8.3 longer than 5 minutes. This includes the older 12 valve 6BT. Tends to carbon up the injectors if idle speed is below 1200 rpm.

diesel don · #8 01-12-2004, 02:34 PM

I'm referring to when I'm away from a plug with my TD. If its single digits or colder, the car runs for substantial periods of time. I've noticed that the temp stays warm enough for the engine concerns.

My only other concern is if the oil gets high enough in the engine on low rpm's. As for our coach busses with Detroits in them, they have a 'high idle' switch so they'll throw more oil.

I use to let my Volvo D run forever with no apparent problems over the nine years that I owned it. As for my MB's, I'm kind of experimenting. As PS said, they only sip fuel at idle. Something like a 1:14 ratio when compared to running. Sure seems better than the pain of 'hard starts' and all the moaning that occurs during warmup.

Don

#9 01-12-2004, 02:57 PM

The longest I've let it idle is 4 hours while at my Diesel instructor used it as an example in class.

I have been told that if one is going to let it idle for extended (longer than 2 hours for example) periods of time, the engine should be set at a high idle. But don't forget about the 1000RPM IP governing limit

.

#10 01-12-2004, 03:10 PM

Since it's abot 60*f today, I'm thinking about running a little test.

Get a measuring cup of about 4 cups. Fill it up to 3 cups with Diesel and put the suction and return fuel lines into it (As one does like Diesel Purge.) Start it, let it idle for 1 hour when at operating temp and noting how much it uses. That should be able to be converted into however long you might want to idle. Due to the age of these engines, every one is diferent so this would be just a general measurment.

Think it would work?

BIGRED · #11 01-12-2004, 09:42 PM

This post raises some interesting questions, for me.

I assume that if there were 4 cars, one each in New York, Chicago, Miami and Los Angeles, that once they reached normal operating temp, the oil temp would be simular.

If that is true, then different oil weights would have the greatest impact on starting, when the oil temps. would have the greatest difference.

If that's true then once the engine is circulating oil, no matter where you live, you can drive off. This assumes that the correct weight is used, for the climate in that region.

Don

whunter · #12 01-12-2004, 10:55 PM

Oil weights are critical impact on starting.

Quote:

Originally posted by BIGRED
This post raises some interesting questions, for me.
I assume that if there were 4 cars, one each in New York, Chicago, Miami and Los Angeles, that once they reached normal operating temp, the oil temp would be simular.
If that is true, then different oil weights would have the greatest impact on starting, when the oil temps. would have the greatest difference.
If that's true then once the engine is circulating oil, no matter where you live, you can drive off. This assumes that the correct weight is used, for the climate in that region.
Don

ericnguyen · #13 01-12-2004, 11:22 PM

If you intend on letting your diesel idle for such long periods of time, you need to change your engine oil much more frequently because idling a diesel creates LOTS of soot in the engine oil, and lots of carbon deposits in precombustion chambers and around glow plugs and injector nozzles. MB diesel engines can only tolerate about 2% soot (remember that the original oil filter design on these engines does NOT attempt to filter soot at all).

Carbon deposits will greatly reduce the heating performance of glow plugs as well as shorten their lifespan, and probably affect injection jets.

Do not compare your MB diesel with big rigs and diesel locomotives. MB diesel engines use Indirect ignition while the others use Direct ignition. Big rigs and diesel locomotives have very large oil capacity, thus it can handle a lot more soot than your MB diesel.

Indirect ignition resorts to precombustion chambers to handle a much weaker injection pressure while direct ignition employs much more powerful injection pressure to blast diesel into the regular (big) combustion chambers. The tiny precombustion chambers are highly susceptible to carbon deposits because of its space constraint. You may want to do an "Italian tune-up" from time to time to clear up the carbon deposits due to excessive idling.

IMHO, you should not idle your MB diesel for such prolonged intervals. 5 to 30 minutes idling at a time should be max.

Best regards,

Eric

ericnguyen · #14 01-12-2004, 11:49 PM

Idling your MB diesel car overnight is not an elegant solution for starting problem. Being a diesel afficionado means constantly seeking a better remedy for any of your diesel's problems.

- Just before winter season, check the valve lashes and adjust them if necessary. Correct valve lashes are extremely important for the ease of starting a diesel.

- Check timing chain stretch. Make sure it does not exceed about 8 degrees.

- Check the air filter to see whether it's clogged, and replace if necessary. Don't forget to check fuel filters (pre-filter and main spin-on one) too.

- Use synthetic oil during winter season because it flows much better than dino oil. This may greatly facilitate the starting thanks to almost instant lubrication.

- Check and refill your battery's water level and fully charge it (using a battery charger) when winter season is coming.

- Check to make sure that all glow plugs are in perfect working order. When the weather is very cold, cycle your glow plugs several times (wait about 30 seconds after glow plug light is gone before starting the next similar glow plug cycle).

- Install a block heater to heat the engine block overnight.

- Add some diesel additive (e.g. Power Service, Redline 85, CRC or Valvoline diesel additive etc...) to increase the Cetane rating (increasing ease of ignition) and maintain the the flow ability of diesel fuel.

In California, it's ILLEGAL to let a car idling without attendance. Also, idling a car outside (not in a garage) is an invitation for car thieves. BTW, do never idle a car in a closed garage. Your life is much more valuable than a big chunk of metal.

Do not idle your MB diesel for too long! methink...

Eric

#15 01-12-2004, 11:56 PM

How about this, why not carry an extra extra heavy duty battery in the trunk and connect an DC to AC power converter (I've seen it at Costco) to power up the block heater. Recharge the battery overnight when you get home. Will this work? If it will, less soot in the air!