glow plug removal and testing on TC 29

[dqdave1]

Since I never removed a glow plug before and my tractor started to be hard to start when cold ( crank for 10 seconds and try to start, along with gray and black smoke, start- stall then hold glow plugs again and it will finally start) I assumed I may have a bad glow plug. I decided to remove all three and test them. Simple Idea. I removed the buss bar , no problem. I began to unscrew the glow plugs; I unscrewed for quite a while and they are still in block; I can see about 4 threads that have backed out of block but something is holding them in block. Before creating a problem, I am writing here. What am I missing? After I remove them, is there a test procedure? I was going to just put three new glow plugs in it, but just saw that they are $48.07 each.

 

[JC-jetro]

Since I never removed a glow plug before and my tractor started to be hard to start when cold ( crank for 10 seconds and try to start, along with gray and black smoke, start- stall then hold glow plugs again and it will finally start) I assumed I may have a bad glow plug. I decided to remove all three and test them. Simple Idea. I removed the buss bar , no problem. I began to unscrew the glow plugs; I unscrewed for quite a while and they are still in block; I can see about 4 threads that have backed out of block but something is holding them in block. Before creating a problem, I am writing here. What am I missing? After I remove them, is there a test procedure? I was going to just put three new glow plugs in it, but just saw that they are $48.07 each.

Glow plug should only help the combustion to start when engine is cold, once the engine is running it is no longer powered. I'm thinking it may something to do with either combustion air or fuel and kind of running reach due to black smoke. On mine when I removed the bus bar(+ terminal) I just unscrewed it CCW and it came out easy. As far as testing, I really don't know what the surface temp needs to be when you turn on the glow plugs, but reading the temp with power and without power should be simple. I would use a non contact type thermometer (Infra Red)if I have one available. The guts of the glow plug is just a resistive wire and it should either work or not and there is no in between. There should be a K-ohm resistance Value for the glow plug that can be measured without disassembly. If there is bunch of soot and contamination caked on the glow plug may prevent it to transfer proper heat for cold start... in that case removal of plug and wire brushing it may do the trick.

JC,

 

[dqdave1]

I even used an air rachet on it; it backs out about four threads and then just spins but will not come out of the threaded bore.

 

[JC-jetro]

I even used an air rachet on it; it backs out about four threads and then just spins but will not come out of the threaded bore.

Hmm. That's strange. Do you have a holder same as reducing bushing on the block where the plug screws in? or does it just screws to the block. On mine there is more than 4 threads before I can remove the glow plug. Do you have the same condition on all the 3 plugs? I did not notice any washers on my plugs that may cause binding with the threads. Did you try to pull it out with hand pressure?

JC,


I hope you have not twisted off the plug in the block. A friend of mine tried to remove a hot spark plug and ended up with twisting it off at the thread neck. I had to use a larger size easy out to remove the plug. At the shop they told him they need to remove the head to remove stuck part of the plug.

 

[dqdave1]

The whole glow plug is turning ( threaded area is turning) It is loose; that is I can wiggle it but something is holding it in block. I did try pliers to no help. I wonder if it has gotten too hot and "probe" has melted and is holding it in. I tried center glow plug and it does the same thing; it was a little easier to unscrew but will not release from block. Mine look pretty close to your picture. Just have three.

 

[DocHeb]

I would evaluate the fuel filter for water, your fuel delivery system to evaluate for gelling of the fuel, and your air cleaner before I start replacing glow plugs. Michigan isn't a whole lot different from Ohio in winter, and my tractor will start on the third turn in the winter on those times I forget to wait for the glow plug.

 

[DocHeb]

You shouldn't have to remove the glow plugs to check their resistance. Put one lead of the ohmmeter on the metal body, and another on the electrical post. For my TC40D, the manual lists the the correct resistances as below:

Coolant temperature:

95 degrees F - 670+/-80 Ohms
176 degrees F - 118+/-6 Ohms
221 degrees F - 54.5+/-2.7 Ohms
239 degrees F - 42.0+/-2.5 Ohms

Of course, you would have to have the tractor started and warm to get the lowest temperature they list, so you're in a bit of a quandry.


Again, your tractor should start easily with only one glow plug working. I think this is a fuel/delivery problem.

 

[WTA]

Can't you just hook the clamp end of a test light to positive on the battery and touch the point to the tip of the plug after unhooking the wires?
If it's working it will light. If it's bad it won't light.
Test lights are cheap.
Your glow plug probably has carbon built up on it holding it in the hole. I really doubt it melted

Check your ground straps and connections on the engine too. No ground path for the plug means they won't work too. That was the most common problem I ever found working on the Kubotas. It's best to take off each cable and use a angle die grinder with a 3m scothbrite pad to clean all the cable ends till they are nice shiny copper looking. Same for the steel place where they attach. Take off all the paint and rust. Then when you reconnect them use some kind of dielectric grease to prevent corrosion.
It's amazing how much difference good grounds will make.

 

[jinman]

The whole glow plug is turning ( threaded area is turning) It is loose; that is I can wiggle it but something is holding it in block. I did try pliers to no help. I wonder if it has gotten too hot and "probe" has melted and is holding it in. I tried center glow plug and it does the same thing; it was a little easier to unscrew but will not release from block. Mine look pretty close to your picture. Just have three.

Dave, I think you have so much carbon buildup on the glowplug sheath that it is bigger than the hole and will not come out. You could try to spray some Berryman's into the hole to soak and soften the carbon, but that also may not work.

Each glowplug has a heating sheath made of stainless steel that extends beyond the threaded outer body. The first step in the repair manual after removal of the glowplug is to remove carbon from the sheath. Also, there is a pecific instruction to NOT measure resistence to the sheath, but to the threaded body instead. (I don't think this will damage anything, but you just won't get an accurate reading.)

This sheath is probably somewhat delicate and it may be damaged trying to remove it if the carbon is severly caked and will not chip off. The most serious problem is if something breaks off and falls into the cylinder. I don't know any better suggestion than to spray in some Berrymans to soften the carbon and then try later.

With carbon buildup this severe on your glowplugs, I suspect also that you might need to have someone look at your injectors or the fuel adjustment. It just seems odd that you would have this much carbon on the plugs.

There is nothing in the removal instructions that mentions anything other than what you have done for removal. I've never removed my glowplugs, so I can't offer you any first-hand experience, but there seems to be nothing you are doing wrong.

 

[ctjstr]

The couple times I've had stuck glow plugs, its been a matter of grabbing the end with vice grips and twisting and pulling to get them out past the built up carbon. Pretty much trashes the glow plug unless you're really careful.