jinma 224 with 2 hours

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.