Just How Glow Can A Glow Plug Glow

[dagwill Senior Member Find all posts View Profile Close dagwill]

My Landcruiser Is Fitted With An Automatic Timer To Acuate The Glow Plugs. I Have Fited An Overide Button To Extende The Cycle Which Aids Starting On Cold Mornings Heaps. Qu. Is There A Critical Time Limit As To How Long Current Can Be Supplied To The Plugs Without Them Burning Out Or Should It Be Possible To Have A Plug Glowing Away Happily Without Self Destructing.

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: Just How Glow Can A Glow Plug Glow

Your battery will go flat before you burn the heaters out.
Glo plugs consume about 10Amps each (give our take a bit depending on size). 6 of them turned on at once=60A. Most batteries (even in good condition) will die in the arse after a few minutes of having that much current sucked out of them. As the voltage of the battery goes down, the current required for the glo plug goes up, which sucks the battery voltage down even further and well its a repetitive cycle.
Glo plugs are a straight out resistive device designed to radiate heat, it is very difficult (not impossible though) to destroy such a device in the circumstances you describe.
David is correct with the assertion that you get no more effectiveness from them once they are hot.

[zigparacingtadpole Senior Member Find all posts View Profile Close zigparacingtadpole]

Re: Just How Glow Can A Glow Plug Glow

Something else I just though of, which further supports my theory that you will have some difficulty killing them and more directly answers your q.
A lot of places that sell conversion kits sell inline heaters that utilise a glo plug to supply the heat. These are normally temperature regulated but this is done so as not to burn the oil passing through the device, not to stop the device destroying itself.

David, I just read your post again, do you by any chance have a teenage daughter, if so it LIKE shows!!

[Vegiecars Member Find all posts View Profile Close Vegiecars]

Re: Just How Glow Can A Glow Plug Glow

Hi Folks, I manufacture an inline heater using a glow plug as the heating element. I am advised by NGK that the glow plugs are designed to be on briefly say 6 seconds. Keeping the glow plug on for much longer than this will burn it out quickly. In the heating units, the glow plug doesn't burn out because it disperses it's heat into the fuel. It is common for my customers to burn out the glow plug on installation because they just can't wait to see if it works before it has been primed with fuel.

Regards
Marcus

[dagwill Senior Member Find all posts View Profile Close dagwill]

Re: Just How Glow Can A Glow Plug Glow

thanks all for response
vegiecars, that was my worry as my timer [before it died] would stay on for about 3 to 4 seconds and
i thought if something generates enough heat to glow red hot in 4 sec that heat would very soon self destruct
i know they remain on constantly in fuel heaters but the cooling effect of a cool liquid is very diferent to sitting in still air
i will tred lightly and with trial and error use the lowest count for a clean start
it seems to be about 7 to 8 sec

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Just How Glow Can A Glow Plug Glow

On my '78 300D engine, it takes 10 seconds for the GP to be hot enought for reliable winter starts on biodiesel/veggie blend. These are the series GPs MB used before 1980.

Tony

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: Just How Glow Can A Glow Plug Glow

In my 300D, I have a home-made glow plug heater which uses a single 14V pencil-type glow plug. My GP heater which sits before the IP is controlled by a 100degC thermo switch, so it is constantly cycling on and off. In actual fact, I thought it was a 24V volt GP as that is what I asked for, but have since noticed that 14V is etched onto it????!!! Previously I was blowing the 12V variety quite regularly (11V etched on that GP). Anyway, this single 24V/14V (whatever) plug has worked flawlessly for the past 10 months and does an excellent job at heating the oil.

I think the secret is to use a nice lump of brass for these GP heaters. They heat the oil that passes though instantly, but as soon as the fitting gets to your selected temperature, the housing does most of the heating and the GP doesn't have to work as hard, so cycles off and on less often. Also, it retains a lot of it's heat if you have stopped for 1/2 hour or so. It will do an even better job if you take the time to insulate it.

BTW, I am getting this reliability from a $10 GP off eBay! A word of warning though. Strip the paint off it before installing it or you run the risk of the paint entering your fuel line.

[timo360 Biofuels Forum Newbie Find all posts View Profile Close timo360]

Re: Just How Glow Can A Glow Plug Glow

To the best of my knowledge, glow plugs keep glowing when the engine is running with no power applied from the heat of the combustion in the cylinder. I think running the heating element which is inside the plug is a different thing however and overly long heating times can shorten their life.

Once the engine is running the glow plugs are inoperative and serve absolutely no function. At my work we have some diesel machines that dont have glow plugs (dont ask me why? cutting costs and lowering complexity probably), they are quite hard to start but run fine once their going

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Just How Glow Can A Glow Plug Glow

TImo306,
Glow Plugs for a diesel engine are norrmally installed in Indirect Injection engines to provide additional heat for engine starting (the prechamber causes a significant loss of heat in the air, during the compression stroke).

Direct Injection diesel engines rarely have GPS fitted. This may be the difference between the diesels at your work.

David was not implying that the GPs were powered up, just that he thought that they would continue to glow due to the heat of combustion in the prechamber, where the GPs are located, once the engine was running.

I doubt that they would continue to be red hot but neither of us has any evidence to support these opinions or else we would have presented it.

Regards,
Tony
ps, check for a Privarte Message from me.

[timo360 Biofuels Forum Newbie Find all posts View Profile Close timo360]

Re: Just How Glow Can A Glow Plug Glow

TImo306,

David was not implying that the GPs were powered up, just that he thought that they would continue to glow due to the heat of combustion in the prechamber, where the GPs are located, once the engine was running.

My bad, I misread his post.
In regards to direct injection diesels, dont the new VW diesels etc have glow plugs? Ive never driven one so i cant say but I thought they did.

That would logically explain why the engines at my work dont have glow plugs

Tim

[DutchAussie Member Find all posts View Profile Close DutchAussie]

Re: Just How Glow Can A Glow Plug Glow

In regards to direct injection diesels, dont the new VW diesels etc have glow plugs? Ive never driven one so i cant say but I thought they did.

Tim

The 1.9 L TDI Diesel Engine in our VW Caddy has glow plugs.

[Qwarla Senior Member Find all posts View Profile Close Qwarla]

Re: Just How Glow Can A Glow Plug Glow

Glowplugs are used for one main reason. To provide heat.

In a large engine with large diameter cylinders there is a lot more distance to the combustion chamber walls. When I say walls I mean all the metal surfaces inside the combustion chamber at Top Dead Centre.

Now on a large engine the distances are much greater and so the heat from compression is not completely sucked into the cold metal.

Now in a small engine these distances are much less and the heat from compression is drawn into the metal and can result in insufficent heat for ignition. The glowplug fixes this problem.

So why don't small industral engines have this problem?
They use a much higher compression ratio to overcome this problem.

If higher compression ratios are used in car engines they then cause more vibration and noise, also they would need to be built stronger, which means heaver.
Simply put it's a tradeoff. Install glowplugs and build a lighter, quiter and smoother engine.

Now some glowplugs do stay powered up for some time after the engine is started. The time will vary with make and model. The was the older type where you had to press and hold a button until the little coil would glow then start the engine. Then came all sorts of automatic timers/controllers.

An interesting experiment. Connect a light between the interconnecting rail of the glowplugs and earth. After heating and startup see how long the light remains on for. You might be surprised. I was.

[Qwarla Senior Member Find all posts View Profile Close Qwarla]

Re: Just How Glow Can A Glow Plug Glow

Hello David,
From what I understand it is thought to help with emissions until the engine heats up more.

You will find with some engines that are manwelly glowed that in very cold frosty or snowy weather that a bit of extra glowing after the initial crank and fireup can help make them run a lot smoother. But we are only talking about the first 30 seconds or so. Once a bit of heat soakes into the combustion chamber glowing is no longer required.

I was surprised to find the plugs stay on in my Triton until the temp gauge is just above the 'C' mark. That takes maybe a full 5 minutes. In my opinion that's way more than required.

A few months ago I found only 1 plug still working and went about finding replacements. New ones from Mitsubishi retail about $73 each. So I looked on evilbay and found some for $9.50ea., a more realistic price.
Unfortunatly the fist lot of them died in a very short time, I think because of the long after glow times. I since replaced them with the same part but installed a switch, between the timer and relay, so I now glow, turn off the switch and crank.
So far so good.

[timo360 Biofuels Forum Newbie Find all posts View Profile Close timo360]

Re: Just How Glow Can A Glow Plug Glow

Qwarla i think that clears it up with direct injection and glow plugs then The glowplugless diesels at my work are small motors, probably around 500cc.
Yes its true diesels do produce more pollutants when cold. They produce more unburned hydrocarbons and more soot, however im pretty sure produce less Nitrous oxide emissions.
I tried your test on my diesel gemini and the glow plugs appeared to go off straight away. Maybe somethings broken or it was before they cared to much about emissions

[BjBlaster Donating Member Find all posts View Profile Close BjBlaster]

Re: Just How Glow Can A Glow Plug Glow

I've had no troubles heating SVO with a glow plug after 40,000km. I use an inline heater with one in it, and it seems to be holding up ok!

here is my setup for those who want a look...

SVO - Straight Vegetable Oil - Engine Conversion.