Glow Plug Use

[HAR]

Tomorrow, I may get a chance to 'test' my glow plugs! Forecast is
Tonight low around -7F. Saturday high near 3F. Saturday Night a low around -6F

 

[HAR]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

 

[mjonesnh]

Believe my New Holland counts actual time tractor is running. Idling vs full PTO speed seems to count at same rate.

 

[Mtsoxfan]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

Where in VT are you. Just got in and we are still at -8. Better than -18 at 3 am. At least the wind stopped.

 

[HAR]

Where in VT are you. Just got in and we are still at -8. Better than -18 at 3 am. At least the wind stopped.

Addison County, near Middlebury...hmmm...as for actual coldest overnight temp....I was tucked snuggly in my bed at 3AM! We are on top of a 400FT hill which makes a difference, and the sky has been clear and sun bright since sunup. Currently 7F in the shade.

 

[Mtsoxfan]

We're as bit further north. Currently -7 in shade. We're at about 1600' but on an east ridge, so wind is plentiful all year round. Damn snow drifts. I was only up at 3 because catalyst on woodstove plugged and issues arose. About to bundle up and see how far I want to snowshoe. Wind picked up, so may be short lived. Hope the weather guessers are off on their amounts of snow tomorrow evening.

 

[HAR]

We're as bit further north. Currently -7 in shade. We're at about 1600' but on an east ridge, so wind is plentiful all year round. Damn snow drifts. I was only up at 3 because catalyst on woodstove plugged and issues arose. About to bundle up and see how far I want to snowshoe. Wind picked up, so may be short lived. Hope the weather guessers are off on their amounts of snow tomorrow evening.

Well, your 1600ft level explains part of it. From my days as a 'student' pilot, I remember that there was approximately a 3°C drop (or 5.4°F) for every 1,000 feet gained in elevation under dry conditions, up to a certain altitude. If it's snowing or raining, the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet. That is why, if you happen to be flying in a passenger airline at 35-40MASL, and the little screen on the seat back in front of you shows some bizarre outside temp of say -40F, you now know why.

While you are correct about the 'weather guessers', it appears we in VT will be in the white by later Monday! Let's hope the tractor starts and no problem arise with the snowblower!

 

[Mtsoxfan]

Never made it out of negative numbers. -6 was the "high".

 

[grsthegreat]

Last year my tractor struggled to start since fall. I wasn’t able to get around to changing the plugs until this spring. Major difference. Today was 12°f, tractor fired up without any issues. Acted like brand new. 10 second auto timed glow cycle, fired off beautifully.

 

[ponytug]

So. It was -5F earlier this morning, and about 2F when I finally got out to try the cold start. While not definitive, it took at least 20 seconds for plugs to be hot enough for the cold start this morning. I cracked the throttle about 1/4 and I tried 10 seconds, then 15, and after the 20 seconds, I got a good start. As tomorrow will be another cold one, I will try once more, and go with 20+ for the first try.

Once started, I wanted the engine to warm up some and I got a chance to answer a long term question. And that has to do with the HOBBS meter. They are calibrated in 1/10 of an hour units or each tenth is 6 minutes. I had mentioned once before that I questioned how the meter worked as I was pretty sure that when the engine was running at low RPM, the meter was not clocking true hours.

Member newbury had said: "Just make sure how the hour meter on the equipment runs.
For example some tractors only count hours at full PTO speed."

Supposedly, my engine is at full power at 2900 RPM. While the engine was running, set at about 2000 RPM, I got my cell phone out and set it to a stop watch and waited for the HOBBS to turn 1/10th. When it did, I started the stop watch. When it turned again, to the next 1/10th, I stopped it. If my HOBBS only works correctly at full RPM, by simple math, at 2000 RPM, the HOBBS should have changed at about 8.7 minutes. As I am not sure the exact RPM, I was somewhat pleased when the meter turned at 8min 2seconds. Working that backwards, I estimate my engine was probably running about 2175 RPM. Ahhh...the things I do when I have way tooooo much time on my hands! Isn't retirement fun!

I'm glad that you've got a starting plan sorted out.

I have several Hobbs units on various engines, and they all run true power on hours, but mine are all voltage driven, rather than a mechanically driven Hobbs.

Thanks for the general rule on altitude driven temperature drops.

All the best, Peter

 

[dkmc]

They’re not training manuals. Kinda like engineering plans for building the infrastructure on a subdivision. It’s not a plan for a carpenter or a mechanic. Certain amounts of knowledge or knowledge, experience and correlation are in order.

Didn't say it was a 'training manual'. Don't need training, need correct info on repairing the machine.
It says right on the front....Repair Manual. I expect it to offer step by step instructions on how to repair the machine. Kinda like a good repair manual works, not lacking steps because the authors cut corners and basically didn't do the research needed to include meaningful content. Your comment makes no sense, but some people will eagerly express their counter opinion just to be able to disagree.

 

[aircommuter]

Well, your 1600ft level explains part of it. From my days as a 'student' pilot, I remember that there was approximately a 3°C drop (or 5.4°F) for every 1,000 feet gained in elevation under dry conditions, up to a certain altitude. If it's snowing or raining, the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet. That is why, if you happen to be flying in a passenger airline at 35-40MASL, and the little screen on the seat back in front of you shows some bizarre outside temp of say -40F, you now know why.

While you are correct about the 'weather guessers', it appears we in VT will be in the white by later Monday! Let's hope the tractor starts and no problem arise with the snowblower!

You need to go back on your student pilot days and study. 3.3f is per thousand feet and no commercial aircraft can fly at that altitude you referenced. I am not student pilot but a licensed pilot.

 

[aircommuter]

I'm glad that you've got a starting plan sorted out.

I have several Hobbs units on various engines, and they all run true power on hours, but mine are all voltage driven, rather than a mechanically driven Hobbs.

Thanks for the general rule on altitude driven temperature drops.

All the best, Peter

Hobbs hours are actual hours the meters are activated typically by oil pressure. Mechanical tachometer hours are average hours based on revolutions. Usually about 60% of actual.

 

[ponytug]

Hobbs hours are actual hours the meters are activated typically by oil pressure. Mechanical tachometer hours are average hours based on revolutions. Usually about 60% of actual.

Perhaps, and I do not work on aircraft, but I've never come across a Hobbs meter connected to oil pressure. As I understand it, oil pressure connections are an aviation use case, but again, not an expert here.

Hobbs meter - Wikipedia

en.wikipedia.org

All the best, Peter

 

[aircommuter]

Perhaps, and I do not work on aircraft, but I've never come across a Hobbs meter connected to oil pressure. As I understand it, oil pressure connections are an aviation use case, but again, not an expert here.

Hobbs meter - Wikipedia

en.wikipedia.org

All the best, Peter

I agree with part of your statement.

 

[HAR]

You need to go back on your student pilot days and study. 3.3f is per thousand feet and no commercial aircraft can fly at that altitude you referenced. I am not student pilot but a licensed pilot.

While I may not be a licensed pilot, if you carefully re-read my post, you will see that I did say "the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet gained in elevation under dry conditions" and I did qualify that by saying "up to a certain altitude" and gave a link to a site that both explains and shows in more detail the expected temperature changes at different altitudes.

And, I have flown in commercial aircraft at FL35-40, which is not at all uncommon on transcontinental or transatlantic flights. Also, as this is a 'tractor' forum I said 35-40MASL (thousand above sea level) which is the same as saying FL35-40, a term normally only pilots recognize.

Today's screenshots are from FlightAware: One showing an aircraft ICAO type B752 (Boeing 757-200) at 40000ft (FL40) from Atlanta to Eagle County in CO and the other showing ICAO type E55P (Embraer EMB-505 Phenom 300) at 41000ft (FL41) from Salina Regional in KS to Raleigh Durham in NC.

[For those unaware, the first line is the aircraft call sign and type, the second line is the current altitude (or FL flight level) and current speed, third line is the departure and destination IATA airport codes and ETA.]

 

[RayIN]

My tractor operators manual says 30" to 1' minute. Note " and ' are seconds and minutes symbols too.

 

[RayIN]

I agree with part of your statement.View attachment 4830795

FWIW, Cummins HD engines of this decade have a feature in the ECM that will not allow an engine start until the ECM "sees" oil pressure.

 

[aircommuter]

While I may not be a licensed pilot, if you carefully re-read my post, you will see that I did say "the decrease is about 1.8°C (or 3.3°F) for every 1,000 feet gained in elevation under dry conditions" and I did qualify that by saying "up to a certain altitude" and gave a link to a site that both explains and shows in more detail the expected temperature changes at different altitudes.

And, I have flown in commercial aircraft at FL35-40, which is not at all uncommon on transcontinental or transatlantic flights. Also, as this is a 'tractor' forum I said 35-40MASL (thousand above sea level) which is the same as saying FL35-40, a term normally only pilots recognize.

Today's screenshots are from FlightAware: One showing an aircraft ICAO type B752 (Boeing 757-200) at 40000ft (FL40) from Atlanta to Eagle County in CO and the other showing ICAO type E55P (Embraer EMB-505 Phenom 300) at 41000ft (FL41) from Salina Regional in KS to Raleigh Durham in NC.

[For those unaware, the first line is the aircraft call sign and type, the second line is the current altitude (or FL flight level) and current speed, third line is the departure and destination IATA airport codes and ETA.]

View attachment 4832554View attachment 4832556

Go back and look you said 3.C under dry conditions.
FL 40 non existent, but you said 40MASL. That acronym is meters above sea level. Once you get above 18,000’ (FL180)it changes to flight levels which eliminates variations in altimeter settings, they all use 29.92 that keeps the spacing equal, plus those are all IFR flights. Altitude and flight levels are two different things. Altitude is expressed with either MSL or AGL. So to clarify 35000’ is a flight level and is expressed as FL three five zero, not 35.

 

[RayIN]

@HAR another vote to do what works for your engine.

I would comment that fuel also makes a difference, and trying to start on summer #2 diesel in the winter instead of diesel #1 will set most diesels back a bit. Add in a bit of gelation, and things are even harder.

Due to the high compression in diesels, and the thermal expansion that happens as the engines warm up, yes most diesels do benefit from gentle treatment until they are thoroughly warm.
Can you use it before then? Sure.
Is it good for the longevity of the engine? Not in my opinion.
Might something else kill engine first? Yes.
It's your engine, but I would do what the manufacturer recommends unless I had a great reason.
Some engines are a lot better at cold starting than others in my experience.

Well, yes, but I would comment that not all "glow plugs" are in the engine, and even in the cylinder, some are a hot tip design and some have an exposed filament; some "glow plugs" are in the intake manifold where they preheat the air for more complete combustion, there are engine intake air preheaters on some Yanmars (and CATs), then you have the delightful thermostart systems on many older Yanmars that basically drip some diesel on a hot filament to ignite the diesel to heat the air intake. Vintage diesels came in hot bulb version where a protruding part of the combustion chamber had to be preheated with a blow torch before cranking.


Having been around diesels, I would say that the manual is about par. So, yes glow plugs are pretty basic to diesel servicing, so I would expect a new trainee to at least know what they are, how they work, and how to check them. Most diesel mechanics probably have worked on a variety of engines, and glow plug control systems, and have a feel for the "lightbulb" nature of a glow plug. Get the ohm readings, if one or more isn't working, they all need replacing. Given the hassle of replacing most glow plugs, I do buy OEMs if possible, or at least from the company that made them for the OEM.

I've owned diesel engines that didn't care much about how cold it was if the battery was in good shape and the engine had a high output starter. I've owned others that you had to sit and wait for everything to get warm before they would catch and turn over happily. In my limited experience, some of the glow plug systems can put a sizeable load on the battery, and if the battery is weak (old, bad lot, sulfated, or just too cold itself) starting can be tough as then the starter isn't turning as fast as it should. There's a reason why there are batteries for northern states and batteries for southern states. The designs, additives, and details like the CCAs change.

I'm not a fan of starting a diesel on one cylinder as that stresses pretty much everything when it is least able to take it. If it doesn't fully catch for me at the start, I'll repeat the preheat cycle until it does.

Good luck on getting your Kubota sorted out.

All the best, Peter

This is what Cummins says about warm-up times.
Temperature Range Warm-Up Time
Below 0°F (-18°C) Up to 7 minutes
0°F to 50°F (-18°C to 10°C) 3 to 5 minutes
Above 50°F (10°C) 1 to 2 minutes