JD 730 diesel shutdown procedure

Hello folks I just picked up a 59 JD 730 diesel in very nice shape and the person I bought it from told me how to shut the tractor down and described the procedure as pulling the throttle back to low idle then pulling the button on the dash that allows the throttle to come back to fuel shut-off but to make sure that I am depressing the compression release pedal as the engine is stopping, he said to never let the engine stop under compression. I have gone through the Operators manual and they mention nothing of releasing compression during engine shut down. I am not say if its right or wrong because I dont know? Could you folks tell me if this is the correct way of doing it and possibly why?

Thanks much
Karl
 

The book does not tell you to do it that way.
The good mechanics will though...
It makes the life of the flywheel and crankshaft much easier..

So it is the right thing to do.
 
That's how a good mechanic told me to do it just think of the weight of that flywheel rocking back and forth
 
We always decompress gas 2 cylinder pulling engines on shut down. The manuals probably didn't say anything about decompressing because they couldn't forsee how hard not doing it would be on crankshaft and flywheel splines.
 
Don Ward advocated the decompression process on shutting down JD 2 cylinder diesels. Don was a high school agriculture teacher in addition to farming. He presented seminars at TWO Cylinder Expos. Great man - rest his soul.

IHC diesels that start on gas and switch to diesel had a somewhat similar question. Some folks said to idle them on diesel for cool down, then switch them back to gas before shutdown. Dad owned a WD9 and we never switched it to gas at shutdown but we did let it cool while idling on diesel.

Sure seems to me that if decompression on JD 2 cyl diesels is needed then JD engineers would have that noted in the OP Manuals. Why is the stress on the flywheel any different during shutdown than
it is during normal running? Seems the cylinder compression is the same either way. Flame me out if somebody has a good mechanical explanation.
 

I always do it just so that the flywheel lands in random positions. Better for the ring gear. My ring gear had a lot of wear in two places.
 
The idea is that using decompression when stopping reduces the "shock load" from the engine hitting the last compression stroke it doesnt have the energy to make, hence causing a sudden reversing. Using decompression allows the engine to coast to a stop, vs "slam" to a stop. Given that many a 2 cylinder diesel suffered from bad flywheel/crankshaft splines, it probably can't hurt.
 
55 50 Ron, I concur, the shock loads on the splines is far far greater when the tractor is working at full load than when the engine is slowing to a stop during shut down. If the tractor needs decompressed to "save" the crank and flywheel during shut down, it then needs decompressed when running at full load. Think about this, the load is trying to stop the flywheel, the combustion process is trying hard to speed the flywheel up.
 

But when it pulling a load , it's pulling on one side of the splines. When you shut it down after the last full cycle of the fly wheel it jerks back and forth. If that makes since.
 
Very interesting topic. Wonder if we could get some mechanical engineers to do a seminar of the topic and set up a series of tests to prove one way or the other what we are theorizing about. I suspect the testing could get quite complicated. Would it come under the heading of torque measurements?
 
Hey guys what you said makes sense to me as per the reason to decompress on shut down, thank you all for taking the time to answer my question on this and it will be done on my 730, thank all again for the sharing of wisdom I have not developed yet, but working on it!
Karl
 
The way I look at it that flywheel gets hammered 50,000-60,000 times per hour when the tractor is under a steady hard load running at 1100 RPMs in he field. I doubt if rocking a couple times when it is shut down will do more damage.
 

If the crank and flywheel splines are so borderline that rocking prevention by releasing the compression is going to save the splines. It is time to install a Taper-Loc.
The primary gain will be allowing the flywheel ring gear to be engaged in various locations .
Various stopping locations also saves the same valve spring from sitting compressed for months at a time .
 
I'm more of the mindset that those splines are hammered much harder when the speed control lever is hard against the fast idle stop and the 555H plow is deep in the western Ohio clay soil than they ever are as it coasts to a stop. Remember these engines start injection 40 or 45 degrees BTC. I'd need to look that up to be certain but it sticks in my mind that's close to the ball park. That's why they have such a pronounced knock to them. That knock also disappears when the speed control lever is pulled rearwaard past the idle stop to cutoff. Seems to me if the splines are so bad that they benefit from decompressing at shutdown, there is a greater problem in this mill about to get real ugly.

The idea that all things come to rest at random positions because of decompressing at shutdown is true. Then again if left alone half the time they'll stop with all 4 valves closed. Which is most beneficial? I deliberately set mine between the #1 and #2 TDC point in the cycles so all valves are closed during a prolonged shutdown. Like mothballing for his long winter's nap.

I'm not saying I know what to do. I'm only conveying what I've considered through the years as I pondered the issue. Yes I have a taperlok flywheel and also a new ring gear and drive pinion. BTDT.

I still think the spline stress likely to be at a max when it's dark out, the tach is down to 1000 or so & you turn off the lights and see that 3" tall cone of dull red exhaust protruding out the top of that oval muffler. Something has him by the tail but he's not giving up and it can go like that for hours and he's probably happier here than in a parade.
 

There is some truth to "windup" in shafts . An example is propeller shafts in ships.
The shaft will operate without fail for decades in "forward" but split after being slammed into reverse a few times .
 

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