Glow question - at what engine temperature can i by-pass the glow cycle.

[ah-kay]

I am contemplating about adding some intelligence in the glow circuit to by-pass the glow cycle when engine is 'hot'. The question is what temperature is 'hot' and engine will start easily without glowing.

any ideas.

[misquick]

I have a 2005 Turbo diesel and I find the indicator lights on my dash showing the glow plugs drawing current when the temperature drops below ~65-70 F. Not very scientific but serves as a guide. I live in FL, my glow plugs are required only in the winter months and only for a short period during the start cycle.

[Skid Row Joe]

*120C

[Skid Row Joe]

Originally Posted by misquick

I have a 2005 Turbo diesel and I find the indicator lights on my dash showing the glow plugs drawing current when the temperature drops below ~65-70 F. Not very scientific but serves as a guide. I live in FL, my glow plugs are required only in the winter months and only for a short period during the start cycle.

Volkswagen?

[ah-kay]

Originally Posted by Skid Row Joe

*120C

SRJ - good try. It is a correct answer but it is not what I am looking for. Thanks but no thanks.

[mach4]

I don't have anything scientific but with my manual glow system I don't bother with GPs if the engine temp is 50C or so and has run in the last hour or so.

[barry12345]

With a warm engine temperature the glow cycle is pretty much already reduced. Even if on a little though may reduce starter effort. Nothing much to save here by making it even more temperature dependant.

Some otherwise good indirect diesel engines in my experience are reluctant to start with absolutely no glow cycle at all even when very warm. This effect was rare for me but posed no problems otherwise.

At the times I never investigated the issues. Just knew the engines wanted a very little glow time hot to light off easily..

There is no absolute answer anyways. All these engines are old and vary widely in condition.

[GregMN]

See page 5 in the pdf.

There is a graph that tells you how long the stock system powers the GP's at a given coolant temp.

[Jeremy5848]

Some of the later preglow systems include a 50ºC switch or sensor in the water jacket to limit the length of preglow and of afterglow. It may be possible to retrofit such a switch/sensor to the '87 300D Turbo and similar models lacking this feature. In the meantime, as a rough guide, I would say that if you turn on the "ignition" switch and the coolant temperature gauge comes up off of the pin, the engine is warm enough to start without glowing.

Jeremy

[OM617YOTA]

Mine starts fine down to coolant temp of ~160F. Probably lower but I haven't tried. It takes a few more cranks than usual but it lights. Glows on and it fires on the first cylinder that comes up on compression.

[Diesel911]

I believe the condition of your Engine, Valve Timing and condition Fuel Injection System are going to determine at what temp your individual Engine can be started without the Glow Plugs.

I think it is the same on your Year and Model; when you are cranking the Starter your Glow Plugs are on regardless what happened when the Key was in the Pre-glow Position.
This entirly makes sense as the Glow Plugs quickly create a much higher heat then the Heat of compression and will shorten the amount of cranking needed to start.

As the other Member indicated a Manual Glow Plug setup allows you to be the intelligence that operates the Glow Plugs.

[Diesel911]

I fogot and the condition of your Starter Motor System is also going to effect your starts.

[OM617YOTA]

Forgot to add, my conversion has manual glows as well, just a switch on the dash.

I usually give it a second of glow even when hot, just because I like the sound of it starting on the very first cylinder that comes on compression, vs. cranking for any length of time. Given the choice, I'll change all five glow plugs five times over vs. doing the starter just once.

[patbob]

You can skip the glow cycle, but why would you want to? What benefit do you think there is to doing so?

If you want to add the intelligence, you'd really need to measure what temperatures you're getting inside the cylinders -- if its not hot enough to ignite the fuel, you needed to glow. Anything else is guesswork, or modeling of a very complex system at best.

[bricktron]

sure, there is an answer, but i bet it differs between even similar engines based on their condition. what on earth is the benefit of not glowing?