Glow plugs not glowing

[Cglaza]

Question for those who know more about this topic. I have a G6200H with 1400 hours. I am having a hard time getting the engine to fire because the glow plugs are not heating up. I am getting battery voltage to the glow plug terminals when I turn the key backwards but they are not heating up. Also I took an ohm reading on each individual glow plug and all three are at 3 ohms and the coil in the dash which I think is called the glow indicator or glow light does not turn red or get hot any longer. Only have about 400 hours on the glow plugs since I last replaced them and the battery seems strong with good crank speed and a resting voltage of 12.6 volts. Any guidance would be greatly appreciated.
Chris

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[dlundblad]

Im not sure what to tell you on the diagnosis part, but a quick way to test them is to remove them and hook them up to jumper cables and a battery. If it doesn***8217;t get red hot, it***8217;s bad.

NGK makes these for Kubota btw. $4ish online vs. $13 at the dealer.

 

[Dave_eng]

Question for those who know more about this topic. I have a G6200H with 1400 hours. I am having a hard time getting the engine to fire because the glow plugs are not heating up. I am getting battery voltage to the glow plug terminals when I turn the key backwards but they are not heating up. Also I took an ohm reading on each individual glow plug and all three are at 3 ohms and the coil in the dash which I think is called the glow indicator or glow light does not turn red or get hot any longer. Only have about 400 hours on the glow plugs since I last replaced them and the battery seems strong with good crank speed and a resting voltage of 12.6 volts. Any guidance would be greatly appreciated.
Chris

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If you are getting voltage at the glow plugs the Glow indicator is good.

The resistance valve of 3 ohms is far too high. Should be just under 1 ohm.

New GP's needed.

Dave

 

[Cglaza]

Im not sure what to tell you on the diagnosis part, but a quick way to test them is to remove them and hook them up to jumper cables and a battery. If it doesn***8217;t get red hot, it***8217;s bad.

NGK makes these for Kubota btw. $4ish online vs. $13 at the dealer.

Thanks for the info dlundblad, I will check that out.
Chris

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[Cglaza]

If you are getting voltage at the glow plugs the Glow indicator is good.



The resistance valve of 3 ohms is far too high. Should be just under 1 ohm.



New GP's needed.



Dave

Appreciate the info Dave_eng. I wasn't sure what the ohm value should be on them. Just surprised they only lasted 400 hours. I will look into the NGK ones and get them replaced. I'll update once I do.

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[Dave_eng]

The quick and dirty test method of removing GP's and applying 12 volts carries significant risk. The GP can over heat and the tip explode.

By passing the Glow indicator is also not wise as it is in series with the GP's and limits the current flowing to the GP's.

From a major manufacturer of GP's technical manual:

TEST CONDITIONS
 Cooling during the glow process: The installed plug is
sufficiently cooled by the cylinder head. If a disassembled glow
plug is to be tested, it must be screwed in a cooling block or a
dismounted cylinder head. If absolutely necessary, the plug can
also be lightly clamped at the hexagon in a vise.

Many have gotten away with the quick and dirty test but a few have not.

Dave

 

[dlundblad]

The quick and dirty test method of removing GP's and applying 12 volts carries significant risk. The GP can over heat and the tip explode.

By passing the Glow indicator is also not wise as it is in series with the GP's and limits the current flowing to the GP's.

From a major manufacturer of GP's technical manual:

TEST CONDITIONS
 Cooling during the glow process: The installed plug is
sufficiently cooled by the cylinder head. If a disassembled glow
plug is to be tested, it must be screwed in a cooling block or a
dismounted cylinder head. If absolutely necessary, the plug can
also be lightly clamped at the hexagon in a vise.

Many have gotten away with the quick and dirty test but a few have not.

Dave

I was not aware of this.

Thanks for sharing.. I definitely wasn’t wearing safety glasses while doing this. You could have very well saved my eyes down the road.

 

[Dave_eng]

I was not aware of this.

Thanks for sharing.. I definitely wasn’t wearing safety glasses while doing this. You could have very well saved my eyes down the road.

Glad you took my comments in a positive light!!!

Dave

 

[BruceP]

The very fact that you are seeing battery voltage at the glowplugs suggests there is no load on the circuit. (glowplugs may ALL be burned out)

When all 4 GPs are loading the circuit, there will be a voltage-drop across the indicator. (This is one of the functions of the indicator... to drop the voltage to the GPs) Infact, as the indicator begins to glow, its resistance goes UP hence dropping the voltage to the GPs as they reach temperature.

A better way to test this circuit is VOLTAGE DROP test. Clip one of your meter-leads on battery+ and the other on the top of the GPs. In this way, you can directly measure the drop between battery and GPs.

I find it VERY suspicious that ALL the GPs would burn out at the same time. If this is the case, I would suspect that somehow the GPs received FULL battery voltage at some point (the GPs should NEVER EVER receive full battery voltage)

I guess what I am saying is that there may be some REASON why all the GPs burned out at the same time. You may need to do some more electrical troubleshooting before firing up the new GPs for the first time. (you do not wish to burn up all the new ones.)

QUESTION: Did you ever use a booster to jump-start your tractor? Some of the boosters put out excessive voltage and could burn up the GPs

 

[Cglaza]

The very fact that you are seeing battery voltage at the glowplugs suggests there is no load on the circuit. (glowplugs may ALL be burned out)



When all 4 GPs are loading the circuit, there will be a voltage-drop across the indicator. (This is one of the functions of the indicator... to drop the voltage to the GPs) Infact, as the indicator begins to glow, its resistance goes UP hence dropping the voltage to the GPs as they reach temperature.



A better way to test this circuit is VOLTAGE DROP test. Clip one of your meter-leads on battery+ and the other on the top of the GPs. In this way, you can directly measure the drop between battery and GPs.



I find it VERY suspicious that ALL the GPs would burn out at the same time. If this is the case, I would suspect that somehow the GPs received FULL battery voltage at some point (the GPs should NEVER EVER receive full battery voltage)



I guess what I am saying is that there may be some REASON why all the GPs burned out at the same time. You may need to do some more electrical troubleshooting before firing up the new GPs for the first time. (you do not wish to burn up all the new ones.)



QUESTION: Did you ever use a booster to jump-start your tractor? Some of the boosters put out excessive voltage and could burn up the GPs

Thanks for the comment. To answer your question about jump packs I have never used one. I did jumpstart it with another one of my Kubotas (L2500) but that was last fall. As to the voltage drop test, I did actually do this and got a reading of a tenth of a volt. Did the same from the cylinder head to the negative side of the battery and got a similar number. Being that is a very simple wiring setup I figured that it would be blown plugs. I also measured the resistance of the glow indicator and it was 0 ohms.

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[Cglaza]

The quick and dirty test method of removing GP's and applying 12 volts carries significant risk. The GP can over heat and the tip explode.



By passing the Glow indicator is also not wise as it is in series with the GP's and limits the current flowing to the GP's.



From a major manufacturer of GP's technical manual:



TEST CONDITIONS

Cooling during the glow process: The installed plug is

sufficiently cooled by the cylinder head. If a disassembled glow

plug is to be tested, it must be screwed in a cooling block or a

dismounted cylinder head. If absolutely necessary, the plug can

also be lightly clamped at the hexagon in a vise.



Many have gotten away with the quick and dirty test but a few have not.



Dave

Appreciate the info, never knew that but I've never tested them in that way either. Glad I haven't

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[BruceP]

..... I also measured the resistance of the glow indicator and it was 0 ohms.

This sounds suspicious. Either your meter cannot measure very low ohms....or the indicator is internally shorted. (A shorted indicator would be a reason why ALL your GPs seem to be burned up)

Mine is essentially the same tractor you have. I replaced the GP indicator on my G5200 several years ago.

The previous owner left the oil-drain washer lying on the top of the engine and it shorted out the GP circuit... this burned up the indicator coil.

Our small 3 cylinder engines use a different indicator than other Kubota tractors. (based on the design of the GP circuit) If you need to replace it, make CERTAIN you get the proper one.

 

[North Idaho Wolfman]

Thanks for the comment. To answer your question about jump packs I have never used one. I did jumpstart it with another one of my Kubotas (L2500) but that was last fall. As to the voltage drop test, I did actually do this and got a reading of a tenth of a volt. Did the same from the cylinder head to the negative side of the battery and got a similar number. Being that is a very simple wiring setup I figured that it would be blown plugs. I also measured the resistance of the glow indicator and it was 0 ohms.

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FYI: Most glow indicators will measure 0 Ohms of resistance till heated then the resistance rises very high to keep from over cooking the GP's.

 

[Cglaza]

This sounds suspicious. Either your meter cannot measure very low ohms....or the indicator is internally shorted. (A shorted indicator would be a reason why ALL your GPs seem to be burned up)



Mine is essentially the same tractor you have. I replaced the GP indicator on my G5200 several years ago.



The previous owner left the oil-drain washer lying on the top of the engine and it shorted out the GP circuit... this burned up the indicator coil.



Our small 3 cylinder engines use a different indicator than other Kubota tractors. (based on the design of the GP circuit) If you need to replace it, make CERTAIN you get the proper one.

I don't have any specs for this little tractor. I thought there would be some resistance in it also. I measured it with the key off from stud to stud. I have never replaced the glow indicator and figured that it must do something to control voltage to the glow plugs being that is the only other item in the circuit besides the main switch and the plugs themselves. I'm pretty sure this is the original glow indicator as well. Can I ask why you replaced your glow indicator? I appreciate the comments, they are helpful.
Chris

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[BruceP]

.... Can I ask why you replaced your glow indicator? I appreciate the comments, they are helpful.
Chris

Please reread my append... "The previous owner left the oil-drain washer lying on the top of the engine....."

 

[North Idaho Wolfman]

If your reading a voltage on the GP's when in glow, then the indicator is fine, as the indicator will not pass power when bad, and will not go lower in ohms, it will go higher like infinite when they are bad.

 

[Cglaza]

Please reread my append... "The previous owner left the oil-drain washer lying on the top of the engine....."

Sorry, my bad

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[Cglaza]

If your reading a voltage on the GP's when in glow, then the indicator is fine, as the indicator will not pass power when bad, and will not go lower in ohms, it will go higher like infinite when they are bad.

Thanks for the info NIW.

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[Cglaza]

Just an update, I ordered new glow plugs and installed them. Everything is working good again and doesn't take as long for the glow indicator to glow either so the old plugs must have been getting weak. Thanks for the advise everybody!

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[North Idaho Wolfman]

Excellent to hear!