Pre-heating time?

[9973720wb19]

I've owned a tractor for going on four years, i owned a 3720 cab for a while then traded up to a 4720 cab. in each case, why does the manual say to pre-heat (by pushing in the key) no more than 10-15 secs, but the LED dash reads "wait for starting" or something like that. one would think that the "tractor" is telling you to hold continue to pre-heat. I've never gone past 10-15 secs, but it does seem (especially with the JD engine in the 4720) that the longer I hold in the key the less it cranks before start. any advise?

 

[beenthere]

I seldom hold the pre-heat key in, but when I do it is only for about 5 seconds. Less white smoke when holding longer.

 

[BRBurns]

I believe that if you hold the key in too long either the wireing or the heater element can burn up. Typicaly stuff that is only meant to be used intermitantly is not rated for the current load over longer periods. Thus it overheats. Starter motor is a prime example of this.

 

[greg_g]

You would think that the price we pay for these machines would include a glow plug timer, but it doesn't. So you have to go old-school, and hold the key by guess and by gosh. Holding for less than 10 seconds does no good at all. 10 seconds minimum, and - the colder the air - the longer you hold. Up to 20 seconds. Longer than that, you risk distorting the tips with over-temp. In very cold conditions, this might require more than one 20 second session. But with the direct injection engine and reasonably mild Kentucky winters, I've never needed more than one attempt.

//greg//

 

[glc24]

You would think that the price we pay for these machines would include a glow plug timer, but it doesn't.

Really strange that the larger tractors are like this. Wonder what JD's thought process was for that move.:confused2:
My little 2520 is a no brainer. Turn the key on,wait for the light to go out,and turn the key. Colder days, I would cycle it twice. Real cold days I plug it in.

Greg

 

[greg_g]

My little 2520 is a no brainer.

My Touareg is even simpler, essentially hands-free. I push and release the start button, the glow plug relay is automatically energized. It measures ambient versus engine temp and calculates how long it needs to heat the glow plugs. While that's happening, I'm fastening my seat belt. When the desired glow plug temp is achieved, they switch off and the starter motor engages automatically.

//greg//

 

[beenthere]

You would think that the price we pay for these machines would include a glow plug timer, but it doesn't. So you have to go old-school, and hold the key by guess and by gosh. Holding for less than 10 seconds does no good at all. 10 seconds minimum, and - the colder the air - the longer you hold. Up to 20 seconds. Longer than that, you risk distorting the tips with over-temp. In very cold conditions, this might require more than one 20 second session. But with the direct injection engine and reasonably mild Kentucky winters, I've never needed more than one attempt.

//greg//

Don't think it is a glow plug as such. It is a heating element instead.
Although my Yanmar in the 455 heats when the ignition is on, and shuts off with a timer in 3-4 seconds. The 4300 only heats when the ignition key is pressed forward. Don't think I have ever held it to 10 seconds.

 

[greg_g]

Don't think it is a glow plug as such. It is a heating element instead.

Presumably you mean on yours, and you may be right. I do recall a Yanmar thumper I had years ago. It too had an manifold heater, some folks call them "flame heaters".

//greg//

 

[Wayne_H]

Interesting... I've had my 4400 for 12 years and never used the glow plugs... Starts up on the second rev every time...

Wayne

 

[greg_g]

As long as it starts when you want it to Wayne, that's the important part. I'm guessing you may put it in storage over winter. Only negative impact may be a shortened starting system lifespan (battery/solenoid/starter motor). Your pre-heat system on the other hand - will probably last a lifetime.

//greg//