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.