That was an old thread. "Coolant" out the fuel drain... that would be scary.

 

Attention! DO NOT TRY THIS AT HOME! If you die, burn or blow yourself up, that's on you, not me!

Don't confuse Flash Point with Autoignition temp. Yes Diesel's ignition temp is 210c versus gas which is 280c but the flash point of gas is -43c and diesel is 62c. What does that mean? It means to get a vapor that a flame or spark will ignite, you need to raise the temp of diesel to 62c (144f). To get ignition where gasoline is vaporizing on it's own is down at -43c. It is possible to get diesel to ignite at a lower temp through atomization but that's where some more physics come in. Remember, you need 3 things for fire, fuel, oxygen and heat (energy). It's not the fuel burning, it is the fuel vapor mixed with oxygen in the air and heat to start it off. Once the diesel is above 62c, it is self sustaining. Wanna see a neat trick to show this? Pour some gas in a pan and throw a match in it, poof, big flames. Throw a match in a pan with some diesel and the match goes out. Now you can hold the match above the diesel and it's heat will cause the fuel to vaporize and ignite. Autoignition temp is the temp that when reach the fuel can ignite spontaneously without the need for flame or spark to set it off. Yes, Gasoline has a higher autoignition temp that diesel but that is not what we were talking about.

So, while the "At room temp diesel wont burn. Unless your room is around 400*F. " remark is off, I think you were a bit off too, confusing ignition temp, flash point and autoignition temp.

I just liked the idea of lighting unknown fluids on fire to see what they are! Poor man Spectrometry! Used to supplement taste analysis.
If you think my disclamer on top was unnessasary, just ask the folks who used to make Blitz gas cans...

 

I pulled it up on a "coolant leak" search and forgot how old it was when I replied and brought it back. I couldn't help it though. I pictured a guy under his hood with a bic lighter testing fluids found on his motor...

 

Thats because you are talking about something a bit different.

Autoignition temperature of diesel is 210*C (410*F) you are correct. But that means that at 210*C, diesel will SELF ignite. All by itself; hence the name autoignition.

Flash point is what you are talking about and is very different. Flash point is the lowest temperature a fuel will vaporize into a gaseous mixture that can be ignited. This is what is required for heating a home. This means that at 62*C (144*F) or higher, diesel will give off fumes and can be ignited with a secondary ignition source, such as a match. When you do this, you are not lighting the diesel per say, but rather the fumes given off by the diesel.

So go outside to a puddle of diesel on a cool day and throw a match on it and nothing should happen. Mix that diesel into the air like a heater does, and it becomes ingitable.

Let me relate this to trucks.. Your injector mists diesel fuel into the cylinder, this distributes the diesel in the air and creates a flammable air mixture. Its worth noting that only a specific concentration of diesel/air will ignite. Too lean or too rich and it wont ignite properly or at all. That goes for all gases.

The cylinder compresses the air. As we know, when you compress air it heats it. In a diesel engine, it gets heated above the autoignition temperature of diesel. And when that temperature is reached, the diesel ignites, creates combustion and we have power.

Also, heating oil and diesel are not technically the same thing, just very close and often interchangeable for the purposes of heating. Heating oil has its own ATSM standard.

 

when its cold i light diesel in a half a coke can to heat engines all the time. it lights just fine in -20f

 

Nobody said it would not burn but you have to raise the temp of the fuel high enough for it to form vapor mixed with air for it to light off. You only have to get it above about 144f, that's not hard to do with a match burning around 600-800c.

A/Ox4 said what I did but with different words. A couple of years ago when he said, "At room temp diesel wont burn. Unless your room is around 400*F." is what I believe started the contention.

 

Yeah, I did not form my words eloquently in that post.

But I think we now know what I meant. Whether I said it or not

Also, I totally missed your post above mine that said the exact same thing as me.

 

I guess I was thinking more in terms as Skip1970. Throwing a can of fuel on the brush pile does atomize it to a degree.