Leave the diesel running??

Cruiser , I switch off @ $ 1.50 plus a litre .

Leaving diesel running might relate more to trucks etc

But all engine will last longer if there not turned off .......heating & cooling thingo

cheers nick

leave it running, millions for and against but really the most damage is done in the first few seconds after start up and on the first rev there is practally NO OIL PRESSURE ...... and that equates to wear, fuel is cheap compaired to rebuilding eh ...... up here it is alway hot so we dont turn off unless we need to as ac is running always and also a deisel needs to be run at idle for a few mins not seconds to cool down properly ...............
Cheers
Joe

Hi Cruiser 74

Don't belieive everything you read on this forum.

The reason is that the turbo in modern diesel engines spins at a ration of the engine revs. That being the case it is constantly increasing and decreasing in revs much greater than the engine revs. Hence it gets very hot.

Once you turn off your engine it takes time for the turbo to cool. If very hot it has a greater chance of ceasing. Letting the engine idle after running give the turbo time to cool down before being turned off. Many modern diesels have a "turbo timer" built in. This will spin the turbo or keep the engine running for a few minutes after you turn off the engine. Once it has cooled below a certain leve the engine/ tubo will switch off.

You can buy a after market turbo timer and have it fitted to your cruiser. Then you just switch off and walk away even though your engine is still running.

Mate do what you want, either way it's not going to hurt and as for wear at startup you won't notice any extra wear, the oil film left on moving parts is enough to stop any wear unless you start it up with you foot to the floor..... after a few second your engine will have all the oil it needs, but then again buy the time it reached damaging Rpm and load conditions it will have oil pressure.

Bit of an urban myth!

I think this myth came about in the old days when it was a chore to restart an engine.... people would leave them running.

This is myth could also go with the "let the engine warm up before driving".

Just to add to the comments re the turbo. If you have been driving hard in the minutes before stopping then it is prudent to leave the engine idling to allow the Turbo to spin down because as soon as you switch the engine off you lose all oil pressure and the turbos spin at incredible revs. If on the other hand you have been idling around the car park trying to find a spot then it is probably ok to just switch it off.

Hi Cruiser74,
I leave my 1HD-T running, the fuel used at idle is buggar all, it's not going to do your pocket any harm or your Cruiser.
keeps everything ticking over, if it's a hot day the family are happier if the AC is still going, I know I hate sitting in a hot vehicle waiting.
Have a good one.

I understand that the concept of leaving the engine idle until next needed came from the olden days to avoid using the starter motor unnecessarily.

The problem comes about due to the effect of electrons moving through the copper cables and windings of the starter motor at the high Ah's. These electrons move at incredible speed and tend to want to travel in a straight line so at every bend in the wire the electrons impinge on the outer side of the cable and the friction creates both heat and molecular wear. So the less the starter motor is used the better. The escaping electrons often lodge in the cooling system and cause radiator corrosion.

The problem is greater in cars manufactured before 1995 when a scientific breakthrough enabled wires to be manufactured with oxygen-free copper which significantly reduced the friction and enabled the electrons to move at much greater speed through the wires. The later addition of molybdenum produced even greater gains and there is current research into electroplating the wire strands with kryptonite.

There seems to be little evidence yet to support the benefit of utilising a HiClone device in the starter cable to realign the electrons but research continues by individuals into this.

Hmmm,

I am not a diesel owner and had a good laugh at some of the responses.

I decided to have a look through Google and the answer is TURN IT OFF.

But its not that easy... this is what I have found....

The reasons for leaving it running originated in a high compression engine and poor battery and recharging technology back in the 50's to early 80's.

Hard to start when cold, glow plugs to warm the cylinders pre start, sucked power from batteries that did not charge as well as modern batteries do now with alternators instead of Dynamo's.

So delivery trucks and others did not turn the engines off with, stop - starts as the batteries would not keep up with the start load.

The "spin down time" for Turbo's is valid, but 5 minutes???

BMW - Volkswagon and many, many European high powered turbo diesels have Stop Start technology, that kills the engine at traffic lights or when the engine is not needed.

Even Detroit state turn it off.

The start up wear is a myth, modern oils prevent this assumed wear, provided that they are changed regularly. If you don't change oil regularly, then the alleged idle wear is going to be 100 times worse..... :)

FACT: A diesel engine works best under load... which is why trucks use them.

FACT: A diesel engine at idle (no load) creates incomplete combustion, leading to carbon build up on valves, in the crankcase oil,in the combustion chamber, causing piston rings to wear. This is why Diesels need more frequent oil changes. Deposits in the engine oil cause wear.

That carbon is often seen after a down hill decent where the throttle is used lightly, the first dab on the throttle produces smoke, burning the excess carbon.

So the real answer is a mix of common sense.

Drive hard, give the engine a few minutes to let the turbo spin down.

Low speed driving, including much of the 4WDing, much done at low speed, you can turn it off as the low speed of the turbo won't matter, but, that is if you are not going to restart in a few minutes.


Just don't leave the engine running if the police are around.....

Years ago I use to deliver pizza.

I found that if I left the car running at each delivery, I used less fuel than if I turned it on and off at each time.

Hi mate,
If you read the pooperating manual for most machines it will state for you to leave the engine idle down for between 3 and 5 minutes. This is for an engine that has been working.

I worked for a guy on dozers and his rule was. If you want to stand beside the machine and have a l;eak leave it running, if you want to get off and walk away idle it off for 5 minutes and shut it down or find yourself another job.

I have no problem shutting an engine down and restarting ias it is still hot with oil up in the engine.

Short and cold running are life shorteners of diesels.

I reckon anyone thats started any engine by crank handle as a young bloke,

would be one of the guys to-day that would say ",Never turn the bastard off"

....LOL.


Cheers Axle.

I drove a vw diesel around Europe. Every time I stopped at a set of lights the car turned the engine off. Touching the accelerator started it again instantly. So much for letting it spin down or whatever... It was a while before I got used to it I must admit. The first time it happened I thought I had broken down after 1 block. :-)

With the pewny little modern motors in our 4wds, i don't think it matters a jot.

If ya motor is 12 litres and the engine block weighs the best part of 2 tonnes, its probably a different story.
Back in the days of cheap diesel and Leyland flat sixes, the brisbane citty council buss drivers where instructed bot to turn their busses off till after their second run...it was considered it took that long to warm the engine up properly....may be?


With older heavy trucks, there where always reliability issues.

If you started a Mack with an air start without letting it run between starts (like moving the truck a few few feet to follow a loader), very soon you would find you where out of start air and looking for some air or a push start.

Because heavy trucks use air brakes, if you where on the brakes a lot before you turn the engine off, ( such as getting into a hole or ducking and shoving) you could find youself short of air when you start back up again.
Particularly when some trucks have a habit of leaking air when you do the wrong thing.

but these are all truck things and have no impact on small 4wds.

on the matter of turbo temperature.
On the OLD Mack I was driving untill recently the largest guage on the dash was the EGT ( exhaust gas temp) guage, you could be flogging the guts out of the old thing, and the EGT could be quite high, button off and the EGT would drop hundreds of degrees nearly immediately, I doubt that the bearing temp would be far behind considering they have their own oil supply.
The turbo components will be going thru drasic tempeature changes all the time the engine is running.

The single biggest thing you can do for your diesel is to change the oil regularly with a good quality diesel spec oil of the correct viscosity.

The other is to avoid short runs at low RPM and low throttle applications.

cheers

G'day Cruiser 74

I hope you have a shovel to get through the pile.

Cruiser74 - Tony V has the correct answers. A diesel engine generates barely-adequate injection pressures at idle, and as a result, combustion is relatively incomplete at idle, because of low injection pressure and a poor injector spray pattern.

An idling diesel engine will generate a substantial amount of crankcase oil pollution from unburnt fuel. The inadequately-burnt diesel stays in the combustion chamber, loads up the cylinder wall, dilutes the oil film, and finds its way past the rings, into the crankcase.

A diesel with a few revs up (800 RPM or more) is generating full injection pressures and the injectors are developing a proper spray pattern and correct fuel atomisation.

In the U.S., in many cities, it is illegal - and you are hit with a large fine, for allowing heavy duty diesels (buses and trucks) to idle longer than 3 minutes. The reason being the high pollutant load from the exhaust at idle.

Cummins engines with PT injection are the worst for poor fuel burn at idle - but all diesels suffer from it, in varying degrees. Because the Cummins uses a unit injector (combined pump & injector), the engine needs more than idle RPM to inject fuel at high enough pressure, and atomise it properly. You never idle a Cummins with PT injection for more than 2 or 3 minutes if you can avoid it.

The only time you need to idle a diesel for several minutes, is directly after a long hard run, when the the valves, the exhaust manifold and the turbo (if fitted) are at a very high temperature (500°C or more). Idling for several minutes in this scenario allows the engine components to cool down, and allows the heat levels in the motor to stabilise.

I bet you're glad you asked, now!

Cheers - Ron.

You might also want to read your insurance policy, if you duck into the shop and come back out to find your pride and joy being driven up the road by an opportunistic thief, the insurance might not consider this theft and may not pay for the loss.

I'm not sure about the other states, but under W.A. & QLD traffic regulations, leaving an unattended vehicle running - even if it's locked - is a chargeable offence. That has been law for over 80 yrs in W.A.
I found reports in the 1934 West Australian newspaper, of court records of motor vehicle owners being fined 10/- in that year, for leaving unattended motor vehicles running.
In this day and age, it only takes seconds for thieves to break a window or screwdriver a lock, to gain access to the vehicle, and that'll be the last you'll see of it.

Turbo timers are a grey area. If you have a turbo timer and remove the keys, apply the handbrake and lock the vehicle and move away from it (effectively "leaving the vehicle running" under the law) - then you probably have a lawful excuse to say that your turbo timer was effectively an approved shut-down method under law.

However, there are no vehicles built in the last 20 or 25 yrs that are able to have the key removed from the ignition and be left running.
So, effectively - if you're going to leave a vehicle idling (apart from a turbo timer), you're leaving it running with the keys in the ignition, and leaving yourself liable to a fine.
As stated, it's also highly unlikely your insurance company would pay out on a theft where a vehicle was left running attended.

Cheers - Ron.

Thanks very much to everyone for your thorough, detailed and hilarious responses! I guess I've got a pretty good idea now albeit a tiny bit confused. My 1HZ is not turbo'd at this stage so that side of things not really an issue for me.

A bit concerned about the lawfulness of leaving the car unattended while idling though. I am always out of the vehicle when the car is idling when I have the compressor hooked up and am putting air back in my tyres...often on the side of the road where I could be seen by Mr Plod. Always have the hand brake on and wheels chocked if I am on an incline or decline. I have never heard of anyone being booked for doing this. I suppose it depends on the definition of "unattended".

I think in the relation to my question I will be switching her off if I'm just ducking into the shops and after a hard run I always have her idling for a bit while I'm pumping the tyres up anyway so that solves that!

Cheers again folks.

Craig