Forum › Forums › Tractor/Dozer Engines › TIMING PROCEDURE ON A Jinma 284
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May 10, 2013 at 5:03 pm #30767
I have replaced the Crankshaft on my 2003 Jinma 284 and I am in need of help to put it back in time. Would anyone be able to help me out with the procedure on setting the timing. Thanks for any help, Doug
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May 10, 2013 at 10:57 pm #36039
For starters, did you mark the positions of the gears in cam train when you took the engine down?
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May 11, 2013 at 12:48 am #36040
I did mark the position fo the gears. But when I was removing the camshaft they rubbed off. Long story short, I reread thru my book and was able to set it, I hope. The factory marks on the gears all lined up with the piston closeses to the fan at TDC. Was able to rotate the cam thru about 78 turns. and the factory marks would line up again. Since the only gear that was taken out was the one on the camshaft, I was able to rotate the other ones because, the way I was thinking was that the other gears would be in time. I just needed to get the camshat gear back in time with the others. Thank you!
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May 11, 2013 at 2:10 pm #36042
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May 11, 2013 at 11:36 pm #36045
Thanks, I should be starting it next week. Looks like I may need a few parts. Thanks for the help, Doug
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May 18, 2013 at 9:52 pm #36070
Ok, after changing out the crank and all bearings. It started on the first try. Oil pressure was about 65psi on a new Mechanical Oil Pressure Gauge. Let it run until the temp came up and ran it around the yard for 30 minutes with no big change in the Oil pressure. Got the bushhog going since the yard was chest high in weeds. After about 1.5 hours of that the oil pressure has come down at speed to about 25psi and idle 12psi. Would anyone know what the Oil pressure should be? It seems like I may have read it years ago on the old board but could not find any info on it. Thanks, Doug
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May 19, 2013 at 6:25 am #36072
I do not know exactly what it should be ,but 25 seems low at running speed.check around the oil filter housing there might be a oil pressure adj.screw there,it is under a acorn nut.that might be able to help you out.Just as a guess 50 psi would be a good pressure on a engine at operating temp.and operating rpm.are you using 15/40 diesel oil?
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May 19, 2013 at 8:11 am #36073
Yes on the oil weight. My concern is that after just replacing the crank, would you think that the oil pressure would drop after running for a short time? Is that normal? Thanks, Doug
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May 19, 2013 at 8:32 am #36074
Oil pressure always drops as the oil heats up with use. These Chinese tractors don't usually run very high pressures anyway. Your readings are in the range of normal, as I recall.
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May 19, 2013 at 9:03 am #36075
That is great news! When I check it the AM it is back up to 65psi running and at idle 50psi when cold. Would you know what the normal range is? It seems like a drop of 40psi is a lot. Thanks, Doug.
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May 19, 2013 at 9:29 am #36076
Glad you got it running again Doug.
What Rich said.
These tractors must have impeccably clean radiators since they don’t have oil coolers like some high end equipment. Give your radiator fins a good careful cleaning.
Many people, including myself, install furnace filter media in front of their radiator, works like a charm.
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May 19, 2013 at 11:20 am #36077
When the tractor was in half I did clean the radiator. So I am guessing that there are not specs on the range of Oil Pressure for the 284. The reason is because I was thinking I might adjust it. I had adjusted it trying to troubleshoot the low oil pressure problem that lead me to change the crank. Also when I put it back together I took out the thermostat, living in Louisiana I thought it might run a litter cooler. Would you think I need a thermostat? Thanks, Doug.
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May 19, 2013 at 12:00 pm #36078
I know it sounds counter-intuitive, but running without a thermostat can be a bad idea, especially when the cooling systems are marginally designed. What can happen is the coolant doesn't spend enough time in the radiator core to allow it to cool properly, so the end result is approximately zero ΔT. Optimum ΔT is around 12°F – 15°F. Install a good 180°F thermostat.
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May 19, 2013 at 12:03 pm #36079
Just out of curiosity, what is your temperature gauge reading when you get the low oil pressure?
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May 19, 2013 at 12:09 pm #36080
It was reading about 180 to 185 or so. This is a new gague that was installed less than a year ago, no power needed to run it. Thanks, Doug.
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May 24, 2013 at 2:56 am #36097
When you replaced or had the crankshaft turned , did you replace the oil pump with a new one ?
If not all the oil that may have caused you to replace the crankshaft most certainly was run through the oil pump .
The pressure regulation is controlled by unseating a ball and bypassing the oil into the crankcase , so if you used the original pump the clearances are going to be larger than a brand new pump.
When the oil gets hot(thinner) the pump- if well worn (it will no longer actually unseat the relief ball) and may only be producing the pressure you see at the gauge… I would try to adjust the pressure relief to increase the pressure , but it sounds like the pressure #s you quoted are well below the regulation settings, which sounds like adjustment won't work due to the clearances…Even with the oil pressure #s you quoted, It sounds like it should run fine
Now if you installed a new pump and the crankshaft clearances are correct, you should be able to adjust the pressure. You could also try a new pressure relief spring, it is possible for it to lose tension.
I agree with Bob on the re installation of a thermostat, many engines need more time for the antifreeze to dissipate heat in the radiator, before being returned to the engine block
Good Luck my 2 cents
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May 29, 2013 at 7:41 pm #36109
Ok thanks, I did change the oil pump and put a thermostat back in, I used a 165°F. Have you seen the inside of the oil pump? There is not much too it. Talked with Jerry at Affordable, and did adjust the relief/bypass oil. The oil pressure reading now, when cold at idle around 100. When hot around 50 at speed and 20 at idle. I may indeed order a new pressure spring to see if that has an impact. Thanks for all the change, keep it coming. Thanks alot, Doug
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May 29, 2013 at 10:21 pm #36110
Why would you want more oil pressure than that? You do know that you can too much of a good thing when it comes to oil pressure, right? Pressures in excess of design limits can actually end up washing out your cam bearings and other things. 20 psig hot is plenty for one of these engines. Keep in mind it isn't revving to 6 grand like a Mazda – as long as the oil is getting around and through the filter, all is pretty much well. Get over 100 psig and you may well blow a filter up, too.
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May 30, 2013 at 10:20 am #36111
Rich, I would think that 100 psi is a bit high but when it gets hot it comes down. Before I had the bearing problem this engine never had oil pressure over 20 psi. I have not been able to find what the oil pressure specs are. Would you have them? My thinking on why the pressure is so high when it is cold and comes down by 50psi when hot was maybe the spring for the oil bypass would heat up and loose a good bit of tension. I can not think of any other reason why it would drop by 50 psi. I had not thought that I could blow something with high pressure, but a very good point. Thanks, Doug
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May 30, 2013 at 10:22 am #36112
Oil bypass spring question? Since the china made spring may be a problem to you think that maybe a higher quality spring would be in order? Thanks, Doug
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May 30, 2013 at 12:54 pm #36113
I have 2 chinese tractors a 20 hp and a 50 hp with different engine manufactures and they both have high pressure at first,so let them warm up some first before turning the rpm's up . I think your oil pressures are what you should have now.
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May 30, 2013 at 3:59 pm #36116
Doug,
Nope – the spring is NOT getting weaker after the engine comes up to heat. Just not possible from a metallurgical standpoint. That spring was hardened at or near 1200°F and tempered at no lower than 450°F so 165°F engine temp ain't a gonna affect it one scintilla. (love those obscure words!)
While I agree that Chinese tractor metallurgy is often a bit marginal, I've never found their springs to be soft. So you're not going to gain anything, except maybe braggin' rights, from replacing it with a spring from Solingen, Germany or Boeing Aircraft.
Any oil pressure over 15 psig at operating temp is sufficient on these tractors. Remember, way back when things like honkin' big steam engines were oiled with drip oilers that had maybe 0.001 psi gravity feed “pressure” and a bunch of those old dinosaurs are still running a hundred years later.
I'm not, I'm just tenderizing the meat!
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May 30, 2013 at 6:18 pm #36117
With that info I think I will adjust the oil pressure back down some. Thanks for all the input and help, Doug
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June 2, 2013 at 10:51 pm #36120
Maybe I have missed it, but you didn't mention what type of pressure gauge you are using. Is it mechanical or electrical?
The reason I ask is the swings in pressure you are getting don't make sense!
I suspect you are using the electrical gauge on the tractor and not a mechanical gauge. I would suspect that the pressure transducer is failing and giving erratic readings.
I would install a mechanical gauge so that you are certain of the pressures you are getting. You can use both and then you will have a good comparison for the future.
My point is, don't trust the pressure transducer in the electrical gauge only – they are known to fail frequently.
Just my $0.02, but might be worth checking into. If you did the rebuild properly and all temperatures are normal, with no increase in engine oil level, there should be no reason for drastic pressure changes.
Thanks
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