Go Bottomdiesel engine dynamics
 | waynerankin
Join Date: Jul 2003 Posts: 1 Sarnia ON 
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2002-07-14 40359
I've just reread the manual. It says to idle/warm up the diesel engine for 5 minutes after EVERY START (after 1 minute or 24 hours uniformly)so my question is, does anyone do this? Does anyone know what the purpose of this is other than to warm up the engine after a prolonged cool down?
Also does everyone turn the key and wait 3 seconds at every start as pre-ignition - and why, since it seems to work turning the key directly ON just like a standard car...
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 | DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada 
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2002-07-14 40360
I don't. I checked my manual (Deere 4100) and it recommends running the engine at 1/2 throttle only in cold weather to warm the engine and hydraulic oils, but only for five minutes. If it stalls it says to restart immediately and resume operations. It also cautions that idling under other circumstances "will waste fuel and cause a build-up of carbon". The only other time it says to idle is after hard usage (2 minutes) to bleed off excess heat, before shutting down. ....
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| DRankin
Join Date: Jan 2000 Posts: 5116 Northern Nevada
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2002-07-14 40361
I forgot to address the subject of pre-heat. It is probably a good thing you have me reading the manual again. My manual is totally silent on the topic. I can find nothing to indicate one can't just turn the key and go. One of our CTB contributors, Peters, mentioned last week that he only bothers with the pre-heat sequence in cold weather. He is highly trained in the area of fuels and lubrication and his advice is good enough for me. I have stopped bothering with it. Strange..... reading my manual one might come to the conclusion there is no pre-heat on this model. I must have gotten that idea from the dealer..? ....
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 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2002-07-14 40366
Unlike a gas engine a diesel uses the compressive heating of the cylinder chamber to provide the ignition source. Naturally the engine is not at it's peak performance unless the engine temperatures are at the designed operating specs. Many diesels will not heat up properly unless the tractor is under load or higher rpm.
The glow plugs provide preheating of the diesel fuel and air or cylinder chamber depending on their location, to enhance ignition at start up. The need for preheat depends on the temperature of the engine block and the compression pressure of the engine. The higher compression diesels had not preheat, you cranked the engine with the fuel off to increase the cylinder chamber temp and then turn on the fuel. My MF Perkins works like this.
Compression on some diesels has been reduced to aid in starting and decrease NOx emmissions, therefore the need for glow plugs.
The preheat on my Cummings is temperature controlled, in the winter the sensor allows the plugs to stay on a few minutes. In the summer they only blink on and back off indicating that the temperature in the cylinder heat is near right. For these reasons I do not bother unless the temperature is approaching freezing. ....
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| Todd Wilson
Join Date: Posts: 1
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2002-07-15 40412
I only use the preheat on my JD 950 in the winter. I also will let it idle for many minutes in the winter before using it hard.
In the summer time I usually will let it run a minut eor so before use and always idle for a few minutes after a hard run to let it cool. After the first start up on a summer day In dont wait any time to start using it as I have a field mowing business and go from job to job.
Now the place I bought my JD 950 from did rebuild the diesel and they said to let it warm up before using it to break the engine in and never to let it idle for more then a minute or so. After so many hours it was considered broke in and then I could start using it a little different then I was. So far its got 250+ hours on it and running great!
Todd
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-07-17 40442
I warm up the engine at around 1500 rpm until the temp comes up into the normal range winter and summer. My reasoning is that engine clearances are really right only at operating temperature. The viscosity of multi-weight oils probably has increased. And, that combustion in diesels isn't complete below operating temperature. Diesels don’t warm up much at rpm’s below 1500
Glow plugs usually provide pre-heating for indirect injected engines. Other types of preheating, such air heaters in intake manifolds are used in direct injection engines. Indirect injection engines usually require pre-heat winter or summer, but direct injection engines may start fine during the summer without pre-heat.
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| W Schober
Join Date: Posts: 1
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2002-07-17 40468
My Kubota 2850 4 cyl manual says to depress the foot feed all the way to the floor before the first start of the day. After turning the key it starts and idles at ablout 1200 rpm for exactly five minutes, then automatically slows to about 600 rpm (normal idle). The book says the fast idle helps pump oil more quickly into the valve train for less wear up there.
Wayne Schober
Sarasota FL ....
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| Todd Wilson
Join Date: Posts: 1
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2002-07-17 40475
I had a 6.2 diesel in a GMC that would not start in the middle of summer unless the glow plugs would cycle. Some just like to have the extra heat I guess.
Todd
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