Glow Plug Use

[HAR]

For those wondering if I checked my battery, I did and do. Mine tested as nearly new.

I replaced the OEM battery once in May 2009 with an Interstate MT51R, just thinking a nearly 10yo battery might need it, and then again in Nov 2022 with a NAPA 7551R, thinking again as I was going into winter with a nearly 13.5yo battery.

As I have previously stated, while I cannot attest to previous starts in 23yrs, I am not sure that any of them were done at much below 30F, as around here, that is pretty much when most snow storms occur. While the glow plugs seem to work fine, I have ordered a set of spares to have on hand, an inexpensive option.

It was and is a question of how long a time should glow plugs be heated before trying a cold start. And so far most suggestions, and the owner's manual indicates, the colder the temp, a longer preheat time is required.

As I said, I did manage to test it one day at 7F by holding the preheat for 20 seconds and it started fine.

While I may have missed a few chances to test at a lower outside ambient temperature, I do plan to do another test, if and when the temps drop closer to 0F or lower. While I doubt very much if I will have to clear snow at those temps, I do use my B7300 to run my PTO GenSet and the power does go out at any temp. I plan to be ready, by knowing what will be needed to get the tractor running, if and when that occurs. Part of that readiness is doing the periodic maintenance run, which I will work into a really cold weather engine start.

Cheers and thanks for all the replies. This is becoming an interesting thread. A lot of good ideas and suggestions for sure.

 

[aircommuter]

The pressure in the fuel systems have increased for better atomization. This also is an advantage for starting of course. There are many variables in engines and types of heaters. While some have a light that goes out after a predetermined time the glow plugs may stay on until another predetermined time or until the start position is activated. Mercedes was one such example. The early models had a glow plug in the dashboard so one could actually see how much it was glowing. Some like the Cummins common rail will start without waiting but will cycle the air intake heater while it is cold for emissions reduction. One can see this happening with momentary dimming of lights or a dip in voltage on the meter.
Like others mentioned test the glow plugs, apply the time as needed and if you are in a very cold area get a block heater. Block heaters are good for keeping the oil warm and engine internal parts warm which reduces startup wear.

 

[HAR]

the warm up times in this chart are for the HST, not the engine. I don't know why it mentions the engine in the last sentence as the engine has nothing to do with it other than how long you are running it. As it says, running with cold hydraulic fluid can potentially do damage.

hube2: While you are correct about the HST fluid, you will also note that the first and latter part of the image specifically states "the engine"

 

[Hermio]

My experience with older Kubota engines is that they really really like glow plugs. The B7000 with the Z650 engine I had would need a very solid 30 seconds to start on about 5ºC temps.

The D640 in my backhoe does better with less glow plug time but still likes it very much.

With this being said, it might be a good time to see if your glow plugs are in good condition. It's possible that at least one is bad, making it harder to start. Just plug the bus bar out and measure the resistance on each one. If it gives an open circuit or very high resistance, means it's bad.

Ditto here. I once had a B7100, and it took 60-90 seconds on really cold days.

 

[ray66v]

In very cold temps, long glow plug times are usually necessary. So, is opening the throttle some.

If you get smoke, or chugging after it starts, you have incomplete combustion. That usually means the glow plug time was not long enough, or you have a bad, or several bad glow plugs. They can also be sooted up, which insulates them from the engine air. Removal, and a light cleaning, will do the trick there.

If the tractor does not fire after cranking briefly, go back to the glow plugs. Continued cranking will only result in a dead battery.

At 6 degrees F, I started my GC with no smoke, or chugging. I used about 30 seconds of glow plug time, and about 1/4 throttle. Have you other hand on the throttle, ready to close it, when the engine fires.

 

[dkmc]

My '83 Mustang skid steer has a D1402 3cyl Kubota. No matter how hot outside, gotta run the glow plugs (replaced and all working) for 1 minute at least. Not 40 seconds, not 50 seconds, 60 or more. Throttle must be set to 1/2, not 3/4 or 1/4. After 60 seconds it fires right up and runs smooth. In summer if it sits off for more than 30 minutes, gotta glow again, but maybe 20 seconds will do. It's finikey to start but runs well enough I don't think it's excessively worn out.

When I got it, it was super hard to start, due to old glow plugs and junky undersized battery cables.
I installed new cables, largest gauge I could get. Made a big difference in cranking speed which is critical that it's fast enough.

 

[ray66v]

hube2: While you are correct about the HST fluid, you will also note that the first and latter part of the image specifically states "the engine"
View attachment 4699378

If you have ac power where you park, a small silicone pad heater on, or near the bottom of your transmission will keep the oil from getting cold soaked, making warm ups fast.

It does not have enough power to heat the oil to high temperatures. So, you can leave it plugged in, when a storm, or other use is expected.

A 4"x5" 150 watt nicely keeps my GC trans. from getting real cold.

And, they are very inexpensive now on Ebay, or Amazon.

 

[Smittyy]

I have 4 tractors on the farm... 1 - 1977 JD 2130, 1- 1978 IH 684, 1 - 1998 Universal 683 DT, and 1 -2022 LS XP8084 with a cab, power shuttle, all the bells and whistles and of course a wonderful DEF regen system. Guess which one is the only pain in the a** to start? OMG... LOL

 

[CubCadetGuy]

Maybe this is an old topic, but I have searched, and while there is some glow plug discussion, I found nothing either serious or in depth.

When using glow plugs to preheat for cold starts, does anyone have any better information or knowledge about what is the proper/correct amount of time to preheat before trying to start a diesel engine?

The reason I ask is this. After having had my B7300 for over 23 years, I had my first cold start issue this past week. In the past, it seems, I really have not had the need to start my engine in really cold weather. However recently, we had a couple small snow storms, nothing enough to warrant clearing the yard and drive, but freezing rain was in the forecast, and following that a much colder freeze. I decided to clear up what was down and around before the rain and freezing rain made a mess, and the forecast deeper freeze turning everything into a rutted skating rink.

As it was about 15F at that time, I put everything in neutral, depressed the clutch, moved the key to preheat, and held it there for 10 seconds, basically what the manual said, and has worked in the past, but I cannot attest to what the temps were when I did those cold starts. However, this time, the engine did not fire on the first try. So, I waited about 1 minute, and repeated the process, and once again, it did not start. So, I repeated it for a third time, and the engine started. I did my clean up and put the tractor away, but I got to thinking about this, as winter here is basically just getting started. I reread my user manual, and confirmed what I had done was what was prescribed.

The next day it was much colder, 7F, and I decided to do a test. I went out and began the cold start procedure, but this time I held the key in the preheat position for 20 seconds, and it started right up. I am now wondering if the user manual is being a bit cautious with the preheat time? Or if maybe there is a more widely used or accepted thought/theory/procedure ?

BTW, Happy New Year 2026 to all!

View attachment 4673726

The challenge is measuring the temperature in the cylinders. All that ignition requires is one hot spot someplace in the chamber when the piston is at TDC. Usually, this will be someplace on the surface of the piston itself or the tip of the glow plug. Designing some sort of temperature sensor that would do something like turn on a non-sustaining indicator lamp is pretty much an impossible task. So the engineers and tech writers are left with recommending something that errs on the safe side. Once you have that first ignition, even if it only partially burns the fuel/air mixture, there will be plenty of heat on that piston head. More heat is going to result in better vaporization, which will reduce how much soot you belch on that first detonation, so they are going to recommend a longer preheat time than what is required to get it started, so as to reduce that puff of soot.

 

[Mcdust]

Maybe this is an old topic, but I have searched, and while there is some glow plug discussion, I found nothing either serious or in depth.

When using glow plugs to preheat for cold starts, does anyone have any better information or knowledge about what is the proper/correct amount of time to preheat before trying to start a diesel engine?

The reason I ask is this. After having had my B7300 for over 23 years, I had my first cold start issue this past week. In the past, it seems, I really have not had the need to start my engine in really cold weather. However recently, we had a couple small snow storms, nothing enough to warrant clearing the yard and drive, but freezing rain was in the forecast, and following that a much colder freeze. I decided to clear up what was down and around before the rain and freezing rain made a mess, and the forecast deeper freeze turning everything into a rutted skating rink.

As it was about 15F at that time, I put everything in neutral, depressed the clutch, moved the key to preheat, and held it there for 10 seconds, basically what the manual said, and has worked in the past, but I cannot attest to what the temps were when I did those cold starts. However, this time, the engine did not fire on the first try. So, I waited about 1 minute, and repeated the process, and once again, it did not start. So, I repeated it for a third time, and the engine started. I did my clean up and put the tractor away, but I got to thinking about this, as winter here is basically just getting started. I reread my user manual, and confirmed what I had done was what was prescribed.

The next day it was much colder, 7F, and I decided to do a test. I went out and began the cold start procedure, but this time I held the key in the preheat position for 20 seconds, and it started right up. I am now wondering if the user manual is being a bit cautious with the preheat time? Or if maybe there is a more widely used or accepted thought/theory/procedure ?

BTW, Happy New Year 2026 to all!

View attachment 4673726

Hi, My '98 New Holland 27 hp comes with a glow system that shuts off at about 5 seconds, and has new glow plugs. In warm weather I find that I need to hold the key in glow position for about a slow count of 10 after the heat light goes out. In this cold (20) Weather a count of 30 is needed for a good start. I don't think it does the engine any good to keep the starter grinding away puffing out smoke and loading the cylinders with fuel. Also I was told sometime ago not to re-heat right away after a failed start, so I say give it to her as long as you estimate it will take for a quick clean start. Happy New Year!

 

[Flogger]

My RTV 1140 is totally dependent on temps. From no glow plugs in warm weather to 15 seconds in sub zero temps.

 

[Jlillie2]

My tractor, which is not a kubota, turns the glo light off, when it is done. It usually takes around 30 seconds or so at the temps you are talking about, shorter if I've had it plugged in. Kubota, Yanmar and Bobcat equipment I have used do the same thing, you hold the key in position until the light goes off. Sometimes it might take 2-3 reps if it is cold and you don't have a block heater.

The B7300 glow plug is manual, its off is the operators hand. (Old school)

 

[Jlillie2]

Maybe this is an old topic, but I have searched, and while there is some glow plug discussion, I found nothing either serious or in depth.

When using glow plugs to preheat for cold starts, does anyone have any better information or knowledge about what is the proper/correct amount of time to preheat before trying to start a diesel engine?

The reason I ask is this. After having had my B7300 for over 23 years, I had my first cold start issue this past week. In the past, it seems, I really have not had the need to start my engine in really cold weather. However recently, we had a couple small snow storms, nothing enough to warrant clearing the yard and drive, but freezing rain was in the forecast, and following that a much colder freeze. I decided to clear up what was down and around before the rain and freezing rain made a mess, and the forecast deeper freeze turning everything into a rutted skating rink.

As it was about 15F at that time, I put everything in neutral, depressed the clutch, moved the key to preheat, and held it there for 10 seconds, basically what the manual said, and has worked in the past, but I cannot attest to what the temps were when I did those cold starts. However, this time, the engine did not fire on the first try. So, I waited about 1 minute, and repeated the process, and once again, it did not start. So, I repeated it for a third time, and the engine started. I did my clean up and put the tractor away, but I got to thinking about this, as winter here is basically just getting started. I reread my user manual, and confirmed what I had done was what was prescribed.

The next day it was much colder, 7F, and I decided to do a test. I went out and began the cold start procedure, but this time I held the key in the preheat position for 20 seconds, and it started right up. I am now wondering if the user manual is being a bit cautious with the preheat time? Or if maybe there is a more widely used or accepted thought/theory/procedure ?

BTW, Happy New Year 2026 to all!

View attachment 4673726

Yea, I found them to be a bit conservative. I generally do around 15 seconds in colder weather. (Or longer)
My dealer also told me that to help it along, you can hold it back on in the glow plug position for a few additional seconds after its running if it seems like its running rough.
(The B7300 is one of the few that can even do this as the key is not in the reverse ignition position like a lot of tractors are.)