Why shouldn't a Mercedes Diesel be left to Idle for long periods. - Page 11 - PeachParts Mercedes-Benz Forum

moon161 · #**151** 01-15-2015, 02:07 PM

Duh!
You should not leave your mercedes diesel idling for long periods because someone other than you may drive it away without asking.

anarchy · #**152** 01-24-2015, 05:08 PM

I find when I sit and Idle for a long period of time say like 2-3 hours that my battery will actually die unless I rev it up a bit now and then.

whunter · #**153** 01-24-2015, 05:43 PM

Quote:

Originally Posted by anarchy

I find when I sit and Idle for a long period of time say like 2-3 hours that my battery will actually die unless I rev it up a bit now and then.

Check for a loose alternator belt.

My best guess = your idle is to low, or the wrong (large) pulley is on your alternator.

.

leathermang · #**154** 01-24-2015, 06:19 PM

Quote:

Originally Posted by 97 SL320

I brought gas engines into the mix because Leathermang insists that once lit, fuel burns 100%. This is completely untrue even with diesel. There will always be a portion that passes through unburnt especially with a pre computer / emission controlled diesel.....

Again you are having to make up stuff in order to argue.
I never said it burned completely....
What I said was that correctly set up... meaning no serious problems like blocked precombustion chamber holes interfering with fuel dispersal.....
that simply reducing the rpm's on our engines does not cause wet stacking.
That is because our engines only work if the fuel ignites due to the hot air it hits when injected.

97 SL320 · #**155** 01-24-2015, 06:33 PM

Quote:

Originally Posted by leathermang

Again you are having to make up stuff in order to argue.
I never said it burned completely....
What I said was that correctly set up... meaning no serious problems like blocked precombustion chamber holes interfering with fuel dispersal.....
that simply reducing the rpm's on our engines does not cause wet stacking.
That is because our engines only work if the fuel ignites due to the hot air it hits when injected.

Actually you did. In your own words from post 114, I've changed your own words to bold font.

Quote:

Originally Posted by leathermang

Some of you are just imagining stuff... like incomplete burn... then stating as fact the results of that imagination.....

once the fuel has ignited you have no reason to assume less than a complete burn..

as for you people suggesting carbon buildup... etc.... that means something is not set properly..
The engine sees idling as just the same as running... except at a different rpm...

leathermang · #**156** 01-25-2015, 10:32 AM

You are proposing.... in suggesting wet stacking at idling rpm's... that LIQUID fuel is left after or during the power stroke to run down the bore walls.... I am saying that no liquid is left if our engines are running.... that all that fuel is changed to a form which exits the chamber via the exhaust valve. I did not say perfect burn...

I said complete burn...all the fuel changed to a combination of the air and fuel and used to power the piston towards the crankshaft.

Here are some concepts which some in this thread have not absorbed.
It is the impression that this ' cold ' air coming into the engine at idling speed is powerful enough to reduce the efficiency of the fuel and air explosion to the point that liquid fuel is left over.

Foremost in their eye's mind is a total lack of confidence in the engine's thermostat.
Second is the realization that the coolant water pump speed is a mechanical relationship to the speed of the engine.... so at 600 something rpm... it is turning at one sixth the speed it would be at 3600 rpm.

The cooling fan on most of our cars is not directly proportional due to the thermostatically controlled clutch. So when working correctly it has the possibility of pulling even less than the one sixth speed which it would if locked up.... but even locked up it can only do the same relationship to engine speed that the water pump does.

So if the engine is running after the glowplugs turn off.... they are needed to overcome the lack of the next concept being ignored... then the air in the combustion chamber is ... bottom line.... hot enough to cause ignition of the fuel air mixture... or the engine stops turning over...

The bore walls.... which are in contact with the water in the cooling jacket... are a huge heat ' bank ' .... but people focus on this ' cold air ' at idle being important..

So lets look at this incoming air with regard to its temperature journey. Lets ignore any effect the turbo on some of our engines have since its effect does not start until higher rpm's.

As it comes into the bore.. being pushed by ambient air pressure only and the space being made by the retreating piston... it is at ambient air temperature...for that flow into the bore.....and about half the next stroke...

at which time the temperature starts being raised by being compressed.... by the end of that stroke it is hot enough to ignite a properly atomized spray of diesel fuel which causes the explosion which drives the power stroke...

so the air is obviously hot on that downstroke....and during the next stroke which only consists of moving it out of the bore to make room for the clean air of the next four stroke cycle..

So out of four strokes.... only one and one half strokes involve ambient cool air inside the bore ..... this is in competition with the aforementioned heat bank of the bore and the dense ( relative to air ) water of the improperly named ' coolant ' jacket.... which is designed to keep the engine at proper temperature... not at too hot... and NOT TOO COOL...

... as the working parts of the inside of the engine are made to work in their Heat Expanded Size.... as an example ... some pistons are not round .. but oval.. due to the difference in the expansion rate of the material constricted by the piston pin boss..but they are round when heated to working temperature....

So during all the other strokes after that first one and one half... the air in the bore is above ambient... most of the time WAY above ambient...

this does not allow for the ambient air temperature to win the competition in affecting the temperature of the engine bores...

and therefor , once running, there is no reason to assume a difference in the function of the engine so drastic as to allow liquid fuel to wash the piston bores.... simply due to reducing the rpm's to idling speed.

pwogaman · #**157** 01-25-2015, 12:28 PM

Smogmonkey · #**158** 02-04-2015, 08:18 PM

waste of fuel and extra wear but in reality

go to spain or spanish isles you will find 100,s of merc diesel taxis idling away all night.
some english truck owners years ago would leave there big trucks idling all night in cold weather
diesel engines idle away 24/7 on water pumps and generators and running saw benches etc