Cold starting a diesel

[Ryland]

Before it gets to cold it might be a good idea to change your fuel filters as not only does fuel gel but the waxes in it harden in the cold along with any water in the fuel will freeze, your fuel filter in your engine bay should have a water drain on it so you can see how much water and crud is in there.
The reasons why diesels don't like cold weather is a long list and any one thing on that list will keep it from running so while you still can, go from head to toe and make sure everything is right.

[robchalmers]

Started first turn of the key. that one nut scupper the whole deal!

that and the temp only dropped to -7 last night

[instarx]

Originally Posted by ConnClark

Air temp isn't the problem. Its mainly fuel temp. Below a certain temp the fuel doesn't atomize or have the vapor pressure to emit vapors to ignite. Glow plugs add heat to the combustion chamber right next to the injectors. This heats the fuel some and adds heat to the combustion chamber walls so it doesn't sap heat away from the compressed air.

This is true - diesels will run at almost any air temperature but the fuel temperature in the combustion chamber at start-up is critical. Almost all vehicles at the South Pole are diesel and they run all winter using a heavily winterized diesel fuel called AN-8 (Antarctic JP8). When it is -70F or below they don't take the vehicles outside because the vehicles themselves tend to break, but the engines will run at those temperatures. They would never start at those temps, but they will run at them.

I just spent the past ten months in Antarctica during the winter, and an interesting observation is that you cannot smell diesel fuel when it is really cold (-50 to -100F) even if you spill it on yourself. It has almost no vapor pressure at those temperatures. As soon as you go back into a heated area you will reek of diesel, but you can stick your nose over an open diesel tank in the cold and you won't smell a thing.

[UFO]

Diesel engines do not depend on fuel vaporizing at ambient temperatures. It requires the heat of compression in addition to glow plugs or some other heat generation in the combustion chamber to vaporize the fuel to the point of auto-ignition. Fuel is injected in such a manner to facilitate this process.

Gasoline is dependent upon vaporization in ambient temperatures.

[ConnClark]

UFO,

All liquid fuels depend on vaporization pressure to some degree. Its the vapors that mix with the air exposing it to O2. If the conditions are just right you can put a match out in gasoline (don't try it). Diesel has a much lower vapor pressure than gasoline, and has a much wider range of where you could put a match out in it(still don't try it).

You are correct that its the compressed hot air that causes it to ignite. You are also correct that fuel is injected in a manner to facilitate this process. However if Diesel fuel is cold enough its viscosity rises to the point it doesn't atomize well. The larger droplets have a much greater mass to surface area than a fine mist does. The larger droplets don't heat quickly enough to burn before they hit and stick to a combustion chamber wall. When this happens they are deprived of adequate O2 exposure to burn properly.

[dcb]

I think my golf likes the half baked mix of bio/kero/dino, fired right up this morning, didn't even smoke a bit.

[UFO]

Originally Posted by dcb

I think my golf likes the half baked mix of bio/kero/dino, fired right up this morning, didn't even smoke a bit.

Mine too. Loves it.

[ChrstphrR]

I found for REALLY cold temperatures (-30 to -40 - doesn't really matter if it's C or F -- it's COLD!!), that I kept a second battery when I lived in those colder temperatures - and I'd either boost, or swap out, depending on how crotchety my Greta would get.

A battery near room temperature has a lot more cold cranking amps available than one that was kept outside with the car overnight in the cold.

I've since moved, and gave away my spare... but I reacquired a marine battery for a failed attempt at making a high capacity UPS for my computer. So, it's the backup battery here now for boosting when things go bloody cold.

Glad to hear in your case it was only an easily found loose/corroded connection. One of my issues that was on again, off again with my diesel ended up being the ignition switch... and two connections running to the starter that involved ripping out half the stuff above the fender to trace up the affected wiring.

Happy oil burning!