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.

 

[kenmac]

It will NOT start in decomp. if functioning properly.

It can't start,,,,,diesel starts on compression. With Dcomp. engaged . there isn't enough compression to start

 

[deepNdirt]

I think depending on what part of the Country we're from,
Some folks refer to "starting" as turning the engine over- via: ( starter ) Some Folks use the term "Cranking"
Others can become confused with either term, I use the term cranking= as cranking the engine over, then the engine starts/runs, But I also know what is meant when refereed to as starting the engine, Turning it over and having it start/run, Oh! and when turning the engine over doesn't necessarily mean turning it upside down,

oh! and I am one of the ones who will slightly pull the throttle open ( I mean slightly ) and then open the Decompression and crank over the engine for a several seconds, When I release the decompression lever it starts right up and runs, However I seldom need to do this, only if the battery has set and run down, It certainly helps to take the load off the starter and also helps to pre-warms the cylinders, doesn't matter to me if it spits a bit of smoke when it first fires up and runs, what matters to me is that it gets fired up and running...beside Isn't a little smoke the nature of a diesel
Oh my! ther's another term can be used ( Fires up )

 

[buickanddeere]

I think depending on what part of the Country we're from,
Some folks refer to "starting" as turning the engine over- via: ( starter ) Some Folks use the term "Cranking"
Others can become confused with either term, I use the term cranking= as cranking the engine over, then the engine starts/runs, But I also know what is meant when refereed to as starting the engine, Turning it over and having it start/run, Oh! and when turning the engine over doesn't necessarily mean turning it upside down,

oh! and I am one of the ones who will slightly pull the throttle open ( I mean slightly ) and then open the Decompression and crank over the engine for a several seconds, When I release the decompression lever it starts right up and runs, However I seldom need to do this, only if the battery has set and run down, It certainly helps to take the load off the starter and also helps to pre-warms the cylinders, doesn't matter to me if it spits a bit of smoke when it first fires up and runs, what matters to me is that it gets fired up and running...beside Isn't a little smoke the nature of a diesel
Oh my! ther's another term can be used ( Fires up )

How does the combustion chamber warm up when cranked with no compression?

Are these compression release systems affecting all the cylinders or half of them?

 

[deepNdirt]

How does the combustion chamber warm up when cranked with no compression?

Are these compression release systems affecting all the cylinders or half of them?

Friction = Heat- although oil may help to reduce friction/heat, but not all together... some heat still remains even if only "Warm"
We all have cranked over an engine before and it not start, then we try it a 2nd time and it fires off and runs, Maybe the fuel maybe friction that helps heat the cyl. that helped to start it up,
I do know a Piston with good rings will create Friction/Heat in the cylinder walls, the extra amount of heat is created of course at detonation, But none the less there is heat created from friction alone,
Example: pull the spark plug out from a small engine, such as a chain saw, although there would be no way you could pull it over as fast as a electric starter, but 5 or 6 quick pulls and stick your finger in the hole, It will be warm,
answer to the second- would be all cylinders are relieved of compression, otherwise if one cyl. still had compression you would note it when on the compression stroke,

 

[bmaverick]

It will NOT start in decomp. if functioning properly.

Mine sure did. There is a difference indeed between not pulling the decomp and pulling it. It takes a little longer to start when the cable knob is normally in the pushed in position. The pull out allows to start eaier, but need to be pushed in right after a start. It' s sort of like a choke.

 

[buickanddeere]

I would like to see a tractor with a properly adjust and 100% functional decompression system. And what the operator's manual says.
If every cylinder is truly decompressed and stays de-compressed. There is no way that engine will start.

 

[normde2001]

Mine sure did. There is a difference indeed between not pulling the decomp and pulling it. It takes a little longer to start when the cable knob is normally in the pushed in position. The pull out allows to start eaier, but need to be pushed in right after a start. It' s sort of like a choke.

Can't happen. Your decomp needs adjusting.

 

[bmaverick]

Can't happen. Your decomp needs adjusting.

Mine sure is happening like that. It will start, but will not run long in that decompression pulled state. Just like the other poster said, chug chug chug wroooom it starts normally. With the decompression pulled it's like wa wa waaa waaaa starts and putters a bunch until the decompression cable is pushed back in. My tractor is a total refurb from the ground up recently from Fredricks Equipment. It's a new cable with all new hardware to the valve cover and linkages.

 

[thunderheart]

Mine sure is happening like that. It will start, but will not run long in that decompression pulled state. Just like the other poster said, chug chug chug wroooom it starts normally. With the decompression pulled it's like wa wa waaa waaaa starts and putters a bunch until the decompression cable is pushed back in. My tractor is a total refurb from the ground up recently from Fredricks Equipment. It's a new cable with all new hardware to the valve cover and linkages.

Well I doubt Fredrick's is infallible and though no diesel expert (my father WAS so some rubbed off) I do know that if the compression is truly relieved the engine can't start. However, my 3110 WILL start with the relief in the rearward position which means that either 1) I am not operating it properly or 2) It isn't truly relieving compression. I happened to service my tractor yesterday and while looking through the engine oil fill hole I operated the compression relief. Though I can see the shaft moving, it doesn't look like it is attached to anything. Sure would love to know how the thing works, and what the procedure for adjusting it is.

As a side note the placement of that thing is a really poor design decision. It interferes with my funnel when filling the tractor with oil. Had to get my wife to hold the funnel while I lifted that 2 gallon jug of Rotella. All basic maintenance operations should require no more than 2 hands in my opinion. Guess they figured you be filling with quarts or one of those handy pumps like they have @ Jiffy-Lube.

Dallas

 

[deepNdirt]

As a side note the placement of that thing is a really poor design decision. It interferes with my funnel when filling the tractor with oil. Had to get my wife to hold the funnel while I lifted that 2 gallon jug of Rotella. All basic maintenance operations should require no more than 2 hands in my opinion. Guess they figured you be filling with quarts or one of those handy pumps like they have @ Jiffy-Lube.

Dallas

also some of the fluid fill holes can be in places awkward to get a bottle/jug into, I realized this when first flushing the hydraulics of my tractor, attempting to hold a 5 gallon bucket over a hole in an area it wouldn't fit wasn't going to happen, I quickly realized I had to first transfer the oil from the 5-gal bucket into a 1-gal jug, and of course by using a funnel that it would filled faster than would drain would become top heavy and tip over, what a mess that was, if ever you change the hydraulic oil definitely get yourself a transfer pump,:thumbsup:
I do have one now, and quite handy for many uses