"New" L345 owner questions

[BigP623]

Decompression is for cold starting - it allows a cold engine to turn over easier. When the starter is turning the glow plugs are powered too. After turning over a few seconds decompressed, push the button back in to start. Overall there's a bitless battery drain using decompression.

At many latitudes it doesn't make much difference so owners ignore it and the cable rusts stuck. It was discontinued on the next models.

For stopping L345 has a small lever on the right for cutting fuel. Later models got a pull-knob.

Makes sense, I appreciate the response.

Actually I appreciate everyone's responses to this point. I didn't think diving into tractor ownership would be such a large learning experience. I have only scratched the surface. Im trying to get all my bases covered and have as much working knowledge of the machine for when we actually put this thing to work.

 

[MagKarl]

Cold air passing hot valves can cause issues, and those issues can turn into major issues.

How does holding the exhaust valves open change that situation? A running engine has hot valves and cold intake air coming in every time the intake valves open. Hard to believe holding he exhaust open a pinch somehow changes what the intake valves see.

You can argue it's better to cut the fuel, but I have a hard time seeing what the cause for damage with decompression could possibly be.

 

[100 td]

I think he means the cooler intake air being pushed back out past the hot exhaust valves. While I wouldn't have thought this would cause damage as the intake air is heated some as it comes into the chamber, I'm prepared to be schooled and hopefully learn the reasons along the way.

 

[North Idaho Wolfman]

How does holding the exhaust valves open change that situation? A running engine has hot valves and cold intake air coming in every time the intake valves open. Hard to believe holding he exhaust open a pinch somehow changes what the intake valves see.

You can argue it's better to cut the fuel, but I have a hard time seeing what the cause for damage with decompression could possibly be.

What can happen, yes very rarely, is that the cold air and now cold diesel fuel, that is pulled in and pushed out past a hot exhaust valve cause the hot stem of the exhaust valve to craze, crack, and eventually break.
The face of the valve see's this change in temp often and has tempered to it, but the stem of the valve normally keeps about the same temp curve, thus is subject to damage.
You see this same thing happen with gasoline engines when they are run without headers or exhaust manifolds installed.

 

[100 td]

Thanks NIW,
I had thought of the term "quenching" of the valve but didn't think the air would be enough, however saturated with diesel as well would add some thermal mass. EDIT: Got me thinking about gas turbines where water is injected to give more power output!