jinma 224 with 2 hours

JohnS · Jan 17, 2005

I have never started mine using the decompression lever, either. But, I did assume it would provide some lubrication and it was probably a better way to go. That seems to be the core of this discussion. Does it or doesn't provide some lubrication at starter speeds?

Has anyone had their valve cover off, and cranked the engine over quickly, with decompression engaged? I believe that you would need to rig up something, like using vise grips, because the lever is part of the valve cover. If oil is getting to the top of the head, then it is most likely getting to other critical areas. Maybe you could do this test by shinning a good light in the oil fill hole. If you see new oil, answers the question. If no oil seen, doesn't answer it 100%, though.

Outside of the lubrication, I do believe there is some benefit just getting things turning when it is ultra cold out. Probably could be argued that it is more a battery issue, though.

Now, keep in mind, all these suggestions and tests are coming from someone who puts his tractor away for the winter! /forums/images/graemlins/crazy.gif

greg_g · Jan 17, 2005

(
Outside of the lubrication, I do believe there is some benefit just getting things turning when it is ultra cold out. Probably could be argued that it is more a battery issue, though.
Now, keep in mind, all these suggestions and tests are coming from someone who puts his tractor away for the winter! /forums/images/graemlins/crazy.gif
)
Things are beginning to be taken outa context here. John - it's unclear toward whom you're directing the "puts his tractor away for the winter" comment. So just in case, rest assured I use my tractors 365 days a year. When they're done for the day, they're parked either outside or in open front sheds.

My 2wd Yanmar with turfs was no good in mud and snow, so it was shedded a few months a year. But having said that - it had ThermoStart, which beats the **** outa glow plugs. The old Yanmar may have had lousy winter traction, it sure did start good in the cold. My KAMA doesn't even have glow plugs, and has not once failed to start. But sure I do remember - vividly - what comparatively hard starters those two Jinmas were in the cold.

Second, I've always maintained in these forums - that the primary benefit of the cold start decompression feature has been to save wear and tear on the starting system. I thought I was pretty clear in the past that upper cylinder lubrication was a fringe benefit of using the compression release for cold starts. If you've ever had to start a tractor with a hand crank, you'd be positively SOLD on the idea of using it for EVERY start. But with an electric starter, once the engine's been fired up for the day - using the decompression lever becomes optional in my book.

Harry, to say that using using the decompression feature can HARM an engine, purely flies in the face of millions of diesel engines - and motorcycle engines - and ATV engines -and airplane engines - that incorporate compression release in one form or another. What an absolute economic and engineering boondoggle it's been, for all those manufacturers have been wrong all these years.

//greg//

Harrygoodwrench · Jan 17, 2005

John,
Point well taken. Now I'm not trying to prove a point or anything like that. It really matters not to me how others prefer to start their engine. This however, is the way I view it. If you were to do the test for oil at the valve cover while cranking it would be inconclusive as the valve train is the last area to get oil pressure. The main areas that takes on wear during start-up are the areas of "high unit loading", main & rod bearings, camshaft bushings, cam lobes and lifters, etc.
Basically the cylinder walls need little lubrication except as splash lube and occasionally as oil cooling jets to "cool" the underside of piston and lube wrist-pins. The high unit loaded areas as I listed(bearings, lifters,etc) take on the most wear when starting as there is no oil pressure and metal to metal contact occurs.
Extensive cranking simulates the same conditions as low/or no oil pressure and accelerates wear. This using of decompression system only reproduces extended cranking.
If you want as little wear as possible the options are. Use only in ideal temperatures, use a pre-lube system, keep engine tuned(includes oil, etc), battery,charging, starting system up to specs etc,,,,,etc. These things are not always possible so we deal with it as best we can.
Like I said, it matters not to me how others start their tractors I just want to bring forth my opinion and the factual reasoning behind my opine.

Harrygoodwrench · Jan 17, 2005

Greg, you are free to believe what you want but that does not make it gospel.
Who died and left you the "self professed" expert on China tractors? I've turned wrenches professionally 30 years now and think I know just a little of what I say. And if I'm wrong I'll step up like a MAN and say so.
If you have nothing nice to say,,,,,,,,,,say nothing..............
Its well known you have a bad attitude toward Jinma's due to your bad experience with 2 of them, which I'm beginning to question. Stick to the subject and we can all get along.
Good day and no response is wanted.

Tractors4u · Jan 17, 2005

( But, I did assume it would provide some lubrication and it was probably a better way to go. )

You may be correct here John. I have never had a Chinese tractor but I have had more than my fair share of grey market tractors, particularly Yanmars, which had compression release levers. The Yanmars had oil pressure lights and each time I would pull the compression release and hit the starter, the oil pressure light would go out, indicating that the engine was getting oil. Am I misinterpreting something here?

Soundguy · Jan 17, 2005

( There is no way you are going to throw sufficient oil on cylinder walls at starter speed even with )

I may be way off base here.. but I always thought the premis of the decomp lever and no fuel during a pre-spinup was to get the oil pump pumping.. that way oil gets to the oil starved / drained down head.. not the cyl walls that are spalsh lubed?

We.. over in the yanmar forum.. also make use of our decomp levers. Most of our tractors don't have glow systems.. but have a cruder 'thermostart' option that burns a tad bit of fuel in the prcomb chamber to warm things up.. still not all units are thermostart equipped.

It is common practice to pull the decomp.. spin a few revs, and then release the decomp and move the throttle up.. that way fuel is no sprayed in during decomp. ( yanmar pumps have that 'all the way back setting' that effectively shuts the fuel down. ( a 2 handed job.. less if you have a foot throttle.. ) Many times a few revs of the starter and the oil light is already out.. or those with added on mechanical gauges are already seeing a few psi of oil pressure bobbing on the gauge...

Is it so different with the chineese units?

Soundguy

Soundguy · Jan 17, 2005

( The high unit loaded areas as I listed(bearings, lifters,etc) take on the most wear when starting as there is no oil pressure and metal to metal contact occurs )

Again.. with the decomp pulled.. seems like that high load is greatly relieved.. and as the oi pump is pumping.. seems like things like bearings are gonna get lube.. um.. faster than in a non-decomped situation here???

Soundguy · Jan 17, 2005

( If you've ever had to start a tractor with a hand crank, you'd be positively SOLD on the idea of using it for EVERY start. )

Amen to that. I've got a 2 cyl JD.. flywheel crank.. and without the decomp petcocks open.. it is a real bear to start.

At work we have one of those big chainsaws with a 6' bar ( sthil?) And unless you have arms like popeye.. you use the decomp button to start it..

Soundguy

Harrygoodwrench · Jan 17, 2005

Isn't the purpose of the decompression system to allow faster revolutions so it can provide the compression necessary to start??????? My point being is, the decompression systems main purpose is to allow the engine to start in the first place, If so equipped. Basically NO lubrication benefits take place during this practice only wear but at least engine runs hopefully and thats the main objective.
Wear DOES take place during this process thats all I'm saying

BTW, Tractors4U, I think what you experienced with the oil light going off while cranking is the oil light was only wired hot in "On" position and not cranking position. I've rebuilt many a engine in my professional career. Takes quite a while cranking to get oil pressure up. I've used a drill to drive oil pumps before starting to run up oil pressure and it takes a bit to get pressure up even using a mechanical gauge.
You guys make up whatever you want, as it is what you want to believe.

greg_g · Jan 17, 2005

( BTW, Tractors4U, I think what you experienced with the oil light going off while cranking is the oil light was only wired hot in "On" position and not cranking position. )
Dont' take my head off again Harry, but it actually does work the way T4U describes. SOP for Yanmar owners is to crank the starter and watch the oil pressure idiot light while holding the compression release open. Soon as the little red light goes out, let go of the compression release handle. Engine starts.

The Yanmar oil pressure idiot light is fed a constant 12v in both START and RUN. The sending unit is a diaphram switch, roughly calibrated so that 0 to ~6 PSI is ground. 12v through the idiot light to ground makes it glow.Complete circuit. At ~7 PSI and above, the there is enough oil pressure to push the diaphram away from ground. Open circuit.

Therefore, in START, the light remains ON till you crank the oil pressure up to ~7 PSI. With the engine running and the switch in RUN, the light remains off, till the oil pressure drops to 6 PSI. I know this from rewiring my own Yanmar.

//greg//

Tractors4u · Jan 17, 2005

Harry, I went back and re-read what I wrote and I was not thorough enough. The light would go off after a few revolutions, not when the ignition switch went to start. It is as Greg_G said.

Harrygoodwrench · Jan 17, 2005

Greg_g,
it is neither my intent nor purpose to "take your head off"
If Yanmars SOP is to crank engine until light goes out w/compression released so be it. However, that does not make it so for all manufactures.
I am very much familar with Yanmar. I've rebuilt several marine diesel Yanmars in the late 70's when they were making inroads to being John Deere's engine of choice.
Ask yourself..... why so few manufacturers use compression releases? too expensive or old technology and not necessary?

Inspector507 · Jan 17, 2005

Brent,
I replaced that idiot light with a gauge and always cranked my Yanmar with the decompression release until the gauge had pressure. I wanted oil where it needed to be when I released it to start.

F100Panel · Jan 17, 2005

Seems I have had a hand in this & to that end I'll try to not single out anyones thread but I do agree with Harry... I too have sent the rod down the distributor bore of many an engine & run the drill on the rod to run the oil pump to prelube after rebuild.. If ya wanna get real technical you check your rebuild under normal oil pressure by counting the number of drips in a given time frame from each rod/main bearing. To do that you hook up a presurized oil tank to the...well I'm getting carried away on that... Surprising how much running of the drill it takes to build up oil pressure..... I agree with Harry..... You may see oil move in the head but I'd doubt there's enough oil pressure in the rods & mains to get that pressurized oil cushion in the bearings with just cranking. To that end I'd like to see an engine start fast as possible & come up to RPM to pump up that oil cushion. If your worried about the oil gallies being totally dry the antidrainback valve in the oil filter when functioning properly prevents that...

What I don't agree with with is any fringe benefit of getting any kind of lube on the cylinder walls durring decompressed cranking. Why? Not enough oil pressure or crank speed to throw lube oil up there. Add to that whats the bottom ring on the stack called? Oil wiper? Tends to pull the lube down off the cylinder walls.... That leads to dry cranking on the rings & I just don't see any benefit... Spinning on decompression may well get you oil up into the head but nothing under the valve cover goes down into the cylinders.... & the other thing that started all this? Catepillar used the heat generated by turning over their old engines with the pony motor using the piston friction to warm the cylinders to start before anyone ever heard of glow plugs... So I guess that would lend some credence to there is FRICTION/wear in cranking....

JohnS · Jan 17, 2005

( it's unclear toward whom you're directing the "puts his tractor away for the winter" comment. )

Greg,
I was refering to myself. My tractor has been stored for the winter, as it has, since I owned it. It is certainly shivering under that tarp right now!

JohnS · Jan 17, 2005

Harry, F100,

I don't have near your experience with rebuilding engines. I have only one car engine to my credit and it was a number of years ago. Prior to start-up, I did pull the distributer, and run the oil pump on a drill. Yes, it does take a little bit for it to come up to pressure. I also repeated this a month latter, because I was busy and the moter still had less than an hour on it. My recollection is, that it pressurized much quicker, given it was not a "dry" motor.

My non-expert opinion is that if there is enough pressure to get oil to the top of the head, it should be enough to get to most critical areas, such as the cam lobes and crank/rod bearings. I am not sure about the cylinder walls, though.

How about this? Has anyone looked at the oil pressure gauge while cranking using the decompression lever? Does it have any reading at all? Sorry, I can't test this till spring.

SPIKER · Jan 17, 2005

Hi all:

I too built quite a few car engines, (no diesel ones though)

decompression lever is to get the engine SPINNING UP not sure if it will build MUCH oil pressure but it will get the crank a moving which means more RPM to carry the engine through the piston compression stroke which is where the fuel ignites while it gets SQUEEZED FASTER than just a slow squeeze where some of the compression can blead off. this becomes more apparent with a worn or damaged engine rings.

as for drill to spin the cam/oil pump drive is more for pumping up HYDRAULIC LIFTERS for the first time (so valves can open/close correctly) and to get some oil flowing through the passages. it really does not BUILD UP enough pressure to FLOAT the crank & con rods. pre-assembly lube is what makes it survive for that first start up... oh btw you also can not do this on most FORDS with out having a distributor dummy as the lube first goes to the distributor base then to crank & cam area and finally to upper half through a smaller dia hole which feeds hyd lifter gally setup.

anyhow I've started my JINMA in - degree temps often enough to know that it does NOT have to have decompression lever on, but glow plugs do need to be on for a few sec. (typically 15~20 sec on outside) mine will start 1st ~3 tries depending on how long she sat and how cold it is... never have used heat(other than 500 wayy halogen shop light pointed at injector pump for 10 or so min prior to starting.) and lately not even that. as there was no power /forums/images/graemlins/frown.gif anyhow lots of grumpy people (sorry not meaning you grumpa) /forums/images/graemlins/wink.gif anyhow just my 2 cents worth but this has gotten lost in angry thoughts. /forums/images/graemlins/frown.gif

MarkM

greg_g · Jan 17, 2005

(
Greg,
I was refering to myself. My tractor has been stored for the winter, as it has, since I owned it. It is certainly shivering under that tarp right now! )
Makes perfect sense now. Didn't consider self-recrimination, and thought off-hand that the other participants used theirs year round like me. Thanks for the clarification

//greg//

F100Panel · Jan 18, 2005

Hey Spiker... Thank You.. To date I think you have thrown out the most relevant post yet. Totally agreed, pre assembly lube does get the job done more than adequately on most engines.. To be honest I've had rebuilds sit in the wrapper for months with preassembly lube generously applied & not had a problem on start up without prelubing... To go to all the trouble of prelube & drip counting is only warranted in a big money engine such as a Hi-performance/hi compression/hi RPM engines & commercial die$el$... On the big buck diesels I throw a LITTLE marvel mystery oil down the injectors before starting a fresh rebuild. Seals & lubricates the cylinder walls for faster initial starts. Yeah, guilty I just can't get away from my penchant for as little cranking as possible & get'em up & running to pump up the oil pressure..

Agreed...The decompression feature is to get the crank spinning as fast as possible for that quick heat generating squeeze that makes for diesel firing....when needed...

Again thanks for cooler thoughts from a cooler head... & Guilty.. /forums/images/graemlins/blush.gif it was easy for the well deserved thanks due to I agree with ya..... /forums/images/graemlins/smirk.gif

Harrygoodwrench · Jan 18, 2005

Spiker has hit the nail right on the head with his statement about getting the engine to spin fast in order to create compression (compression creates heat) which is necessary to ignite the fuel in a diesel, a gas engine also needs that heat to vaporize the gasoline as a liquid can't burn.
Years ago starting systems, batteries were so crude you needed a decompression system.
On a hand start engine it served the same purpose. To get engine spinning faster so you had compression. However wear does occur more during start-up than running. A decompression system is a necessary evil as we want the engine to run.
Thanks Spiker for the great post.