Correct engine idle speed during warm up??

[ray66v]

In the winter, you have cold air that is much thicker, (denser), than it is in the summer. This means there is more air going into the engine when it cranks.

When you have more air than fuel, the mixture can get too lean for it to start.

Since there are generally no computers on these engines, you have to adjust the mixture yourself. You do that of course, by opening the throttle some. More fuel enriches the mixture back to the same level it would be in warm weather.

A good way to determine the proper throttle setting for cold weather starting, is to start cranking with the throttle at idle, and while cranking, slowly advance the throttle lever until the engine fires. Note the throttle setting the engine fired at, and you can try that as the starting point next time.

If the engine does not fire after 5-8 second of cranking, always stop, and return to heating the glow plugs again. Cranking until the battery dies only causes additional frustration.

Sometimes, when it's really cold, and depending on the condition of your engine, you may find you need to heat the glow plugs for 30 seconds or more, to get a good start.

To the OP: Diesel engines cool at low idle speed. You need a nice high idle speed to warm one up in cold weather efficiently. Can't tell you what that is, never owned one with a tach. Just open the throttle until it is running smoothly at a nice speed.

 

[FatTire]

The manual for my Kubota says warm up at 1/2 rated RPM, so for my machine that's 1350 RPM.

 

[Gordon Gould]

My Kabota manual says use 1/2 throttle in the winter. I have found this to much for my liking as it starts rough then races. I open the throttle lever slightly then after it starts adjust it to a smooth running 1200 to 1500 rpm. Summer idle is 900 rpm on mine.
Just find a system where it starts easy and smooths out quickly and you will be OK I would think.

 

[Poopdeck Pappy]

I start mine at idle and after about 10 seconds I bump it up to 1200 - 1300 rpm. Then, after a minute or two, bump it to 1500+/- and leave it there for a few minutes. But we don't have the really cold temps a lot of you guys do.

After the tractor warms up for 2 - 3 minutes, I work the hydraulics slowly to circulate the fluid in the cylinders to the rest of the system.

 

[JerryK]

About 10 degrees this morning, probably about 20-30 in my barn where the tractor sleeps. That area is just outside the 16X40 area I heat during the day. Fired up the tractor [ did not use the grid heater ] then brought it up to about 1200. Lifted the blower up so I could take the timbers under it out, then when and opened the barn door..this all took a couple minutes. Backed it out of the barn, dropping the blower once it was outside and pushed the blower/snow across my turn around area. Ramped her up to about 1400... then went and closed the barn, checked the stove, and put on my winter hat/gloves/locked barn.... maybe four minutes. Went back out and fire up the blower to clean out the snow that was packed in it when I first backed up.. then cleaned about four swipes in front of the barn.. Drove about 500 feet out to the mail box, cranked her up to about 2000... and had at it. That's I the baby'n mine gets.....

 

[zd21]

I agree with Gordon Gould's views. The Kubota Corporation is not an authority on each particular starting situation, so its advice must be generic. Examples of possible user differences include ambient temperature, viscosity of oil used, viscosity index, accumulated engine hours, how heavy a load the engine will operate under after warmup, etc. Look at it another way: Kubota engines provide marvelous durability world wide under all the variety of engine users, climates, oil brands, etc. A fair conclusion is that the engine is not sensitive to how it is warmed up.

 

[crazyal]

I shut it off with the engine at about 1400 rpm and leave it there. That's where I start it and adjust it to around 1300 then let it run (with the clutch depressed) for several minutes when really cold. The sooner you can get the oil flowing to all four corners of your engine the better. 1500 or more sounds like it's racing to me and I think the engine oil will reach the pressure limiter so any faster will not do any good.

 

[dixstir]

I have always let my diesels run 1500 or so during warm up summer and winter, when they run slower at idle they contaiment the oil with turns it black a lot sooner after a oil change. I had a 4 cylinder diesel in a 1956 chevy pickup with over 3 hundred thousand and it was still running good when it went to a new owner, still miss it.

 

[Raspy]

In the winter, you have cold air that is much thicker, (denser), than it is in the summer. This means there is more air going into the engine when it cranks.

When you have more air than fuel, the mixture can get too lean for it to start.

Since there are generally no computers on these engines, you have to adjust the mixture yourself. You do that of course, by opening the throttle some. More fuel enriches the mixture back to the same level it would be in warm weather.

A good way to determine the proper throttle setting for cold weather starting, is to start cranking with the throttle at idle, and while cranking, slowly advance the throttle lever until the engine fires. Note the throttle setting the engine fired at, and you can try that as the starting point next time.

If the engine does not fire after 5-8 second of cranking, always stop, and return to heating the glow plugs again. Cranking until the battery dies only causes additional frustration.

Sometimes, when it's really cold, and depending on the condition of your engine, you may find you need to heat the glow plugs for 30 seconds or more, to get a good start.

To the OP: Diesel engines cool at low idle speed. You need a nice high idle speed to warm one up in cold weather efficiently. Can't tell you what that is, never owned one with a tach. Just open the throttle until it is running smoothly at a nice speed.

This is very misleading and inaccurate. Diesels only fire from the heat of compression. If they cannot produce a high enough compression temperature they will not fire wether there is fuel or not. It has nothing to do with being "lean". They do not run "lean" like a gas engine does, they ALWAYS have excess air, but are not "lean" in the sense that it might prevent them from firing or because it is the wrong mixture. There is always an excess of air unless they are running at full throttle. Rich and lean has nothing to do with starting a diesel like it does on a gasser and adjusting the throttle does not change the mixture. As long as they are getting enough fuel to produce the energy to run and they are producing enough heat, they will start. Diesels cannot warn up very well because they are usually quite massive and they always have an excess of air being pumped through them. This extra air has a cooling affect. There is very little extra heat being produced, and what there is is being sent out the exhaust instead of into the cooling system. You don't have to have a diesel fully warmed up to put it to work. A light load after 30 seconds or so will help it warm up and reduce condensation. Running it for long periods cold is more of a problem because it builds up carbon, causes a lot of condensation and wastes fuel. The condensation is water that is not a lubricant. Imagine the rings running up and down the cylinder walls lubricated by water. It's better to get it warmed up soon with a light load and get the oil to it's proper viscosity.

In Alaska, on the pipeline, many diesels were allowed to idle for long periods to warm them up, or keep them warm and ready to use. This caused a lot of engine failures and extreme carbon build up. It's much better to not baby a diesel. Get the oil circulating, which only takes a few seconds, and then start giving it a light load so it can produce some heat, stop condensing and stop producing a lot of cold carbon deposits. Running cold is the problem.

 

[ddb123]

As you can see, there are a lot of different methods out there and pretty much everyone will swear by theirs as few of us have blown up a diesel. My advice is to start it between 1000-1200 rpms (half my rated rpms would be 1300) and let it warm up where it sounds good, usually somewhere between 1300 and 1500. That's what I do, anyway, and I haven't died from it yet.