Block Heater Surprise

[tcreeley]

My 2003 NH TC30- the glow plugs don't come on automatically when the key is in the ignition, regardless of the gear/neutral I am in. If I don't turn on the glow plugs, they don't come on. - No doubt on tractors with newer features- the glow plugs are controlled differently.

 

[rScotty]

It is hard to explain these complicated things so that everyone knows what you are saying.

There is a automatic variable timer. The time duration is controlled by a temp sensor. The lower the temp the longer the time out.

In normal operation when the ignition goes from off to on (not start) the timer starts and the glow plugs and dash indicator come on. You wait until the timer expires, indicator goes out and you can hear the glow plug relay open, and then advance the ignition switch to start.

If you do not wait for the timer to expire and turn the ignition to start while the glow plugs are on the glow plug indicator goes out and the relay opens, immediately. So it seems in normal operation the glow plugs are never on when the ignition is in the start position.
gg

Nice description, Gordon. I believe that is how the glow plug circuit works with the key positions and indicator light work with the temp sensor/timer on my M59. I've noticed that in moderate (0 degree F) weather if the block heater has been plugged in for a few hours the glow plug time will be shorter, but I don't think there has yet been a time when the glow plugs didn't come on at all.
Another piece for the puzzle: The M59 is a hydrostat rather than a shuttle shift - and the glow plug indicator light comes on the same regardless of whether the HST lever is in gear or in neutral.
rScotty

 

[Thomas]

................................................
Happen to me years back,heater on mice built nest between engine air canister intake start to tractor which must have shook free nest and most of it got suck in, also top head of motor and rad. hose keep eye out for.

 

[MortOz]

So it seems in normal operation the glow plugs are never on when the ignition is in the start position.

My understanding is that the glow plugs draw a reasonably large current, and so trying to crank the engine and run the glow plugs simultaneously would put a noticeable extra load on the battery. That could possibly lower the terminal voltage enough to slow the cranking speed, especially in cold conditions when the battery will already be having to cope with the low temperature. All the diesel engines I have paid close attention to are wired so that the glow plugs are not on when cranking.

 

[crazyal]

Did some starting experiments the last couple days and this morning and there is no doubt in my mind now - The procedure to run the glow plugs independently from the automatic timer by using the start position of the ignition switch with the shuttle in forward works on my 2001 L3010. Intended by Kubota or not, Who knows.

Thanks again Dave !!!

gg

It sounds like, to me, that Kubota intended the glow plugs to be on when starting the engine. By being in gear the safety interlock should kick in preventing you from actually engaging the stater but the glow plugs still come on.

 

[countrybumpkin]

Some tractors even have a key position that will allow manual activation of the glow plugs.

 

[crazyal]

My understanding is that the glow plugs draw a reasonably large current, and so trying to crank the engine and run the glow plugs simultaneously would put a noticeable extra load on the battery. That could possibly lower the terminal voltage enough to slow the cranking speed, especially in cold conditions when the battery will already be having to cope with the low temperature. All the diesel engines I have paid close attention to are wired so that the glow plugs are not on when cranking.

I'm not sure if I would count on that being the case. It's very possible the engineers thought that the air going into the cylinder as the engine was cranking would cool down the glow plug too quickly. I would expect the draw to be maybe 40 amps for the glow plugs so while it's not small if it helps shorten the cranking time it could actually be easier on the battery.

I'm not much of a diesel mechanic and while this isn't directly related on older gas engines they used a ballast resistor. It's job was to reduce the voltage on the electronic circuit reducing the load from the coil. That also reduces the power going to the spark plugs. When starting the resistor is bypassed to provide a more powerful (hotter) spark to help the engine start. It would add more load the the electronics as well but the duration would only be a few moments. I've met plenty of back yard racers who have wired up 12 volts directly from their starter switch and have burnt up ignition modules because they didn't use a ballast resistor. So I can see how an engineer could spec the battery size to include a load

 

[RoyJackson]

Some tractors even have a key position that will allow manual activation of the glow plugs.

John Deere requires a manual activation...

 

[Gordon Gould]

The real question is why is that method of energizing the glow plugs undocumented by Kubota. You can guess at it, but that is all it is - a guess.

I hoped that someone with intimate knowledge from Kubota would chime in with the answer to that.

gg

 

[Kubota 2350]

When I was a child we would play in the family Ford Galaxy and if we turned on the four way flashers and step down on the brake we could listen to the radio with out the keys.

I remember those days