Decompression doing anything?

[Scotty Dive]

I can take a pic, but yes the decomp is like the "choke" pull cord that you would find on any lawn tractor. It has a rigid wire instead of a cable though.

Mine is a pull type on my 2020d. The comment of not adding fuel until oil pressure is up and full compression is interesting and makes sense to me

 

[Todd8665]

Somebody here is badly missing the point of decompression .
If you read the manual I assume it reads something like starting a two cylinder Deere diesel.
With fuel shut off, engine decompressed rotate until oil pressure registers. Continue cranking and apply compression. After a rotation on compression add fuel.
Cranking with the fuel on and decompressed is ridiculous as it wets the combustion chamber head, piston and cylinder walls with raw fuel. Next the crankcase oil becomes diluted with diesel.
The wetted combustion chamber also causes "startup knocking".

Thanks for posting this. I have started the tractor with the decompression lever activated with the fuel on and wondered if it was the wrong thing to do, so I stopped. I now, as you said, pull the lever let it crank to get the oil pump running and everything lubricated - stop cranking - release decompression lever MOST of the way- turn on fuel - then crank again.

Question is how one would ever throw the thermostart switch into this routine.

 

[buickanddeere]

I don't know why the operator would stop cranking one oil pressure registers?restore compression and the start cranking again?
When in cold weather in particular . When the starter is rolling the engine over at high rpms without compression. Keep cranking/continue cranking. Add compression and then as quick as you can add fuel fuel.
I've seen cold starts work that way when the the battery could not start cranking the engine with compression applied.

 

[Todd8665]

I don't know why the operator would stop cranking one oil pressure registers?restore compression and the start cranking again?
When in cold weather in particular . When the starter is rolling the engine over at high rpms without compression. Keep cranking/continue cranking. Add compression and then as quick as you can add fuel fuel.
I've seen cold starts work that way when the the battery could not start cranking the engine with compression applied.

Well you got me there. Answer me this though. How do you throw in heating the thermostart into this equation?


BTW - My oil pressure light never goes out when i crank with the decompression level pulled. It disappears almost instantly once started.

 

[buickanddeere]

Did not see anything mentioned about a thermostart until your last post.
Airflow through the intake is very limited while the engine is de-compressed.
Off hand I would say crank decompressed with the thermostart energized. Continue cranking and quick as reasonably possible. Drop the thermostart, add compression and add fuel in that order.

 

[Scotty Dive]

Did not see anything mentioned about a thermostart until your last post.
Airflow through the intake is very limited while the engine is de-compressed.
Off hand I would say crank decompressed with the thermostart energized. Continue cranking and quick as reasonably possible. Drop the thermostart, add compression and add fuel in that order.

I know on mine - the engagement of the TS is CCW on the ignition switch and held for (about 20 seconds or more for me - This is the amount of time needed for the TS to open the valve and have diesel drip on the coil - yours might be less than mine but I verified on mine this winter). Then trying to start the tractor you move the key CW. I am assuming that the TS is turned off doing this, but I thought I read somewhere that it turns on again with the engagement of the key to turn the starter. Anyone verify that? In reading the Hoye Manual I have it says to pull throttle completely rearward (Full Throttle), Pull out decompression lever, Turn key to TS until light goes out and then turn key to start position and crank engine until it is spinning freely and then release decompression lever. The engine should catch and then adjust throttle to 1/2 or 1500 rpms or less to warm up. It does not mention to turn the engine over until the oil light goes out which is what I do. A previous poster mentioned not to put the throttle on until after the decomp is released. That does makes sense to me in not having fuel wash the cylinders down, but it seems on my tractor you would need three hands to do that. One on the key, one on the decomp lever and the other on the throttle

 

[winston1]

I can confirm on my 2002d the thermostart is energized when the key is in the crank position. I have checked it with a volt meter. Whether this is normal or not I do not know. Just know what mine does.

 

[bmaverick]

Well, I tried starting with the decompression pulled out yesterday. I was very surprised it worked. It worked really well and the start to idle was much smoother.

Guess I learned something about starting my Yanmar.

 

[California]

YM240 wiring diagram shows an optional jumper between the crank and TS terminals on the ignition switch, ie power goes to the TS when the key is turned CCW and also when CW to Start position. (Mine's wired that way).

 

[normde2001]

Well, I tried starting with the decompression pulled out yesterday. I was very surprised it worked. It worked really well and the start to idle was much smoother.

Guess I learned something about starting my Yanmar.

It will NOT start in decomp. if functioning properly.