bad for glow plugs?

[bgott]

Glow plugs don't heat the combustion chamber, they heat the pre- combustion chamber in an indirect injection engine. A direct injection engine doesn't have glow plugs, it has a heater to heat the intake manifold. The pre- combustion chamber engine, like an older Ford pick up with the 6.9 engine or the Mercedes diesel, is just about impossible to start with out heating the glow plugs. If the engine starts I wouldn't worry about it. You're not going to hurt the plugs or the engine.

 

[Kodiak]

In twenty two years the glow plugs in our old kubota L345 have had to be changed several times. There is no timer, you just hold the starter switch over till they are warm enough to fire that deisel fuel on the first revolution or two. If it doesn't fire then, repeat the process. As they get older they do take longer to heat up. They also build up a layer of carbon, that I suspect slows the heat radiating from them. Usually they blow a fuseable link or trip a circuit breaker in the glow plug circuit once they resistance gets to high for them to operate properly. And thats when I have replaced them.
Twenty two years, 1590 hours, changed glow plugs twice, just par for the course of her life.

 

[Ozarker]

........and the mixture in the pre-combustion chamber goes where?

http://www.freeautoadvice.com/diesel/glow.html

http://amghummer.com/Maintenance/DieselGlowplug.htm

http://www.ott.doe.gov/pdfs/jtb_diesel_engine.pdf

It's not a matter of your opinion or my opinion, it's a matter of physics. There is a reason you're supposed to wait for the light to go off:

1. Because the length of time the plug heats determines how high the air temperature gets and

2. Because the #1 cause of glow plug failure is over heating.

If you add the heat of ignition to the heat of the electrical current acting on the element, you will reduce the life of the element......period.

Use to have to replace the Cummins glow plugs in military 2 1/2 and 5 ton trucks regularly because young troops would hold the switch on a few seconds after the engine started. With current flowing through them and the engine running, they overheat.

 

[GlennT]

An observation somewhat off the track... I don't normally use the glowplugs on my JD 670 with indirect combustion chambers. The engine seems to start just as quickly and easily without using the glow plugs. Bear in mind that I'm using the tractor in south-central Texas with temperatures above 70 degrees. Even though the tractor doesn't seem to need the plugs, I've wondered if there are benefits to using them that I'm not aware of.

 

[Soundguy]

It is more likely that the resistance of the glow plug drops ( as it begins to fatigue and fail ), allowing more current to flow, thus allowing the breaker or fuse to pop, or allowing the glow plug to 'open'. Higher resistance will yeild lower current flow in a circuit, thus less heat at the element, and less of a chance a fuse or breaker will pop...

Soundguy

"Usually they blow a fuseable link or trip a circuit breaker in the glow plug circuit once they resistance gets to high for them to operate properly"

 

[GSS]

Mine seems to be the same. The light goes out when you turn it to the crank position, but the manual says nothing about 2-3 seconds. Just "wait until the light goes out"...

 

[GSS]

I'll start it a few more times and get a better feel for the time it takes to go out. They'll definitely be hearing from me if it's much different than yours. Thanks!

 

[RoyJackson]

"Even though the tractor doesn't seem to need the plugs, I've wondered if there are benefits to using them that I'm not aware of. "

Glenn, I've the same tractor you have. I use my glowplugs if the ambient temperature is less then 40°.
The sole purpose of them is to aid cold weather starting.

 

[GSS]

It's essentially new (ie warranty never activated), but it has 30 hours on it...

 

[bgott]

They were holding the switch for more than a few seconds then. Mercedes diesels leave the glow plugs on for 15 to 60 seconds after the light goes out, depending on model. Ford uses a post heat cycle on the Powerstroke. There are a few others also. Here is a link to a company that advertizes a two minute post heat. I've seen VW diesels that would take a month or two to burn the glow plugs out with the controller stuck and the glow plugs burning all the time. I doubt very seriously he'll burn out his glow plugs by starting the engine before the light is out.

http://www.beru.com/e/products/02/