Testing glow plugs

[coloradotrout]

I'm suspecting my glow plugs are bad. The timer of my 4100 never turns off, so they have been heating for 100s of hours. I removed the timer and am ready to replace the plugs. Do I pull them out, ground them and see if they glow? What's a way to test?

It seems these -- http://www.amazon.com/NGK-Y103V-Glo...=2025&creative=165953&creativeASIN=B001QITX3U -- are suitable replacements although some of the comments suggest these can take 15 to 30s to heat. I'll be manually activating, so that's fine with me.

 

[Tx Jim]

The way I was taught to check glowplugs is to disconnect the wire from glowplug and using an amp meter with 2 wires attached ,attach one wire of amp meter to positive post on the tractors battery and attach other wire to GP contact post then read ampere draw. No draw then bad GP.

 

[k0ua]

The way I was taught to check glowplugs is to disconnect the wire from glowplug and using an amp meter with 2 wires attached ,attach one wire of amp meter to positive post on the tractors battery and attach other wire to GP contact post then read ampere draw. No draw then bad GP.

Keep in mind you are looking for approximately a 20 amp draw per plug, so quite a lot of current. Of course you could do an ohms check with your ohmmeter as an alternative idea. I am not sure about your glow plugs but the Kioti plugs are about .76 ohms per plug.. That is less than 1 ohm. Hard to read, make sure you calibrate your ohm meter by shorting its leads and knowing what it says when they are shorted.

 

[DFB]

Book just says to ohm test between terminal tip to thread body and read resistance. Good plug between 0.3- 0.5

 

[Tx Jim]

I personally think the amp test is more accurate than the ohm test.

 

[George2615]

Like James said. Test with an ohm meter. That's how I found mine were bad on a previous tractor. No reading or change means its an open circuit plug. Full reading to 0 means its shorted. If you get a resistance reading its probably good. But by you saying your timer never turns off could point that direction too. My timer functioned properly even with bad glow plugs. Came on for 6-10 seconds and shut off as it should.

 

[k0ua]

Like James said. Test with an ohm meter. That's how I found mine were bad on a previous tractor. No reading or change means its an open circuit plug. Full reading to 0 means its shorted. If you get a resistance reading its probably good. But by you saying your timer never turns off could point that direction too. My timer functioned properly even with bad glow plugs. Came on for 6-10 seconds and shut off as it should.

Dont forget the relay also..the timer circuitry could be fine, and the glow plugs themselves could be fine but if the relay itself has burned up contacts... well it could be a lot of things.. some are pretty easy to eliminate as soon as you do some tests..

 

[k0ua]

I personally think the amp test is more accurate than the ohm test.

I don't disagree, but a lot of folks wont have the equipment for the amp test. Most can come up with an ohm meter.

Another way to test is to use one of those lazer thermometers. and spot on each glow plug to see if they heat up..

Of course a simple voltage test on each plug will tell you if the timer and relay are sending voltage to the glow plugs at all. It wont tell you if each glow plug is good or not, but it will tell you that you have problems upstream. relay, timer, fuse wiring etc.

 

[coloradotrout]

My timer is bad. I was getting 12V all the time at the plugs. I'm guessing that burned out the plugs.

Here is what lead up to this -- http://www.tractorbynet.com/forums/...ting/302669-4100-wont-start-cold-weather.html

I disconnected the timer, and will use the PTO switch / Gear Selector work around noted.

Interesting about the 20A post. The plug wires are not that heavy.

 

[k0ua]

My timer is bad. I was getting 12V all the time. I'm guessing that burned out the plugs.

A quick check and you will know.

 

[arlen4720]

an extreme redneck hillbilly quick check is to see if the headlights dim when you activate the glow plugs. You can't diagnose individual plugs, but it'a a good quick check of the control circuit and to see if all the plugs are burnt out.

 

[PILOON]

A glow plug is basically a resistor so the ohm test is just fine.
They should all read the same value or real close. Different tractors with different plugs would give different values, but all low.
Just don't forget to remove each lead in order to get individual readings.
In many cases just removing and replacing the leads might just cure your problems due to bad connections.
High amp connectors like glow plugs and battery terminals need to be clean and corrosion free. (grounds also).

 

[coloradotrout]

Update - I replace all 3 plugs with the ones I noted above from Amazon. Exact fit. $8 each with free shipping once my wife added in some Christmas gifts!

Remove the air filter assembly (loosen hose clamp). Remove the muffler (3 bolts - add some PB Blaster). Remove the metal bracket that the air filter strap connects to. That gives you clear access to 3 plugs.

Last eve it was about 35F. The daytime was around 40. Usually this would present a starting problem for me. Remember, I removed my timer (the failing component). I put into L, turned ON the ignition for about 20s, put into N, and it fired right up like it was 80F outside.

My guess is that timer -- which left 12V continuously applied -- burned out all the plugs, and I've been "cranking" for years not knowing my plugs were dead. I don't plan to replace the timer. The manual approach is just fine and gives me more control.

 

[alchemysa]

If they are bulged at the tip then they are definitely shot. (But thats doesn't necessarily mean that if they are NOT bulged they are fine.)

 

[Norm W]

A test lamp won't tell the truth as it will light with a bad plug. If you make a test lamp from an old head light the amp draw is high enough to give you the truth. If the end of the plug has bulged out you might not get it out of the hole. The fix for that is removal of the head and more work than you probably want.

 

[coloradotrout]

A test lamp won't tell the truth as it will light with a bad plug. If you make a test lamp from an old head light the amp draw is high enough to give you the truth. If the end of the plug has bulged out you might not get it out of the hole. The fix for that is removal of the head and more work than you probably want.

For $8 each -- and the time it takes to get to them. If the engine starts hard in cold weather -- replace them all ;-)

 

[topstoy]

Another way to test is to use one of those lazer thermometers. and spot on each glow plug to see if they heat up..

What about touching the glow plug while heating, can you feel any temperature from the outside of the plug? Never tried it but thinking I might for a quick check. My 2520 seems like it is initially firing on only 1 cylinder for 3-4 seconds. Sounds bad!!!