Decompression

[oldjeepman]

Hello from Hot Springs National Park, Arkansas. Being new to Yanmar diesels I would like to find out about the decompression system. If its on there I want to use it right. What is its purpose? When do you use it? Why? Any info is appreciated.

 

[oldjeepman]

Hello from Hot Springs National Park, Arkansas. Being new to Yanmar diesels I would like to find out about the decompression system. If its on there I want to use it right. What is its purpose? When do you use it? Why? Any info is appreciated.

 

[SailorBob]

Are you referring to the compression release? If so, hold it open for a few seconds when starting the engine. It allows the engine to turnover faster and aid in starting. Especially nice in cold weather.

 

[SailorBob]

Are you referring to the compression release? If so, hold it open for a few seconds when starting the engine. It allows the engine to turnover faster and aid in starting. Especially nice in cold weather.

 

[pruntyc]

One generally holds it open, turn it, in other words or on some they tell me you pull it, never had one like that though. But you hold it open till the oil light goes out, showing the oil pressure is up then release it all the while cranking it. And it makes it easier to start. I used it even if the weather wasn't cold, as it let me know the oil pressure was up, and not giving me a dry start.

 

[pruntyc]

One generally holds it open, turn it, in other words or on some they tell me you pull it, never had one like that though. But you hold it open till the oil light goes out, showing the oil pressure is up then release it all the while cranking it. And it makes it easier to start. I used it even if the weather wasn't cold, as it let me know the oil pressure was up, and not giving me a dry start.

 

[normde2001]

When you pull the handle it opens the exhaust valves. On first start for the day, I like to engage it and crank until I see oil pressure, (light goes out, or gauge rises). For cold weather starts, set throttle, engage decomp, hit the starter then disengage decomp, starts easier. I don't need it for cold weather starts, mine starts almost instantly and I don't work in less than 60 degree weather.

 

[normde2001]

When you pull the handle it opens the exhaust valves. On first start for the day, I like to engage it and crank until I see oil pressure, (light goes out, or gauge rises). For cold weather starts, set throttle, engage decomp, hit the starter then disengage decomp, starts easier. I don't need it for cold weather starts, mine starts almost instantly and I don't work in less than 60 degree weather.

 

[Roonabeck]

The manual I have suggests pulling out the decompression lever when turning the key to the thermostart position (for cold weather starting). Then re-closing the decompression lever as you turn the key over to the crank position. Since the thermostart burns some fuel, this seemed like it was intended to vent the exhaust gasses from the thermostart. However, I haven't started mine in cold weather yet. Have none of you guys used the decompression lever for that purpose?

 

[Roonabeck]

The manual I have suggests pulling out the decompression lever when turning the key to the thermostart position (for cold weather starting). Then re-closing the decompression lever as you turn the key over to the crank position. Since the thermostart burns some fuel, this seemed like it was intended to vent the exhaust gasses from the thermostart. However, I haven't started mine in cold weather yet. Have none of you guys used the decompression lever for that purpose?

 

[Cord]

I'm 90% certain that the thermostart is in the intake manifold, not the cylinder, so I don't see how pulling the decompression handle would affect anything. I only use it for bleeding the fuel system and building oil pressure before starting.

 

[Cord]

I'm 90% certain that the thermostart is in the intake manifold, not the cylinder, so I don't see how pulling the decompression handle would affect anything. I only use it for bleeding the fuel system and building oil pressure before starting.

 

[Roonabeck]

Well if that's true, then you're probably right. I'll go see if I can find that paragraph in my manual.

 

[Roonabeck]

Well if that's true, then you're probably right. I'll go see if I can find that paragraph in my manual.

 

[pruntyc]

Cord, I'm 100% sure, just take off the air cleaner and use it and you can see it in operation. The decompression lever is just for starting in cold weather. I used it anytime I started the first time, cold or not, as then you have the oil pressure up and don't have a dry start. The John Deere I have now, don't have that feature, I kind of miss it, but don't need it as it starts fine, without it. But then again mine has glow plugs, where as my Yanmar didn't.

 

[pruntyc]

Cord, I'm 100% sure, just take off the air cleaner and use it and you can see it in operation. The decompression lever is just for starting in cold weather. I used it anytime I started the first time, cold or not, as then you have the oil pressure up and don't have a dry start. The John Deere I have now, don't have that feature, I kind of miss it, but don't need it as it starts fine, without it. But then again mine has glow plugs, where as my Yanmar didn't.