Jinma 304 tractor was running with low pressure at idle. Now no pressure at all.

[bgarretson]

My 304 has had low pressure when idling for a couple of weeks. When mowing of tilling at full RPM's the tractor was more or less fine. When I left idling the pressure would drop fairly low and the oil light would come on. (this all happened after the tractor warmed up)
Today as I was mowing and the pressure gauge dropped to 0. I pulled off the throttle and disengaged the PTO and the tractor died. I have started it up since and it will run but does not sound good. The change in the sound of the engine is subtle but at idle now the tractor dies. I have not moved it from where it sits and do not plan to until a conclusion is reached.
What may have happened?
What should I do?
I am a mechanical novice as you may be able to tell.
Thanks
Brian

 

[greg_g]

You didn't mention engine oil, and it's not my intention to tarnish the seller. Whether you buy your tractor new or used, it's important to know up front what kind of oil is in the sumps. Don't know how it is these days, but not long ago they were still being shipped across the Pacific with used oil. Competent and responsible dealers knew enough to drain out the domestic Chinese crap, flush thoroughly, and replace with a quality aftermarket product. This applies to engines (to include cooling systems), gear boxes, and hydraulics.

If it's a used tractor, perhaps the previous owner put in the wrong engine oil. First off, they require diesel-rated engine oil. The same stuff you put in your gas-powered car simply won't do. 15W40 is typically recommended, and a lot of us like Rotella T. So on the chance you've got the wrong oil in the crankcase, change the oil and filter - then see if there are any positive results regarding pressure.

Assuming the gauge is accurate, these engines can be operated safely (on the correct oil) down to about 6-7psi at hot idle. When started cold, they may jump up above 40 psi. But as the oil thins, they typically work well in the 20-30psi range. If you need help converting the metric markings, let me know.

That said, we have documented an occasional oil pump failure on these forums. Doesn't happen often, but it too can result in zero psi and an engine shut-down. Or it could be a blocked pickup screen. Might now hurt expose the oil pump and examine the pickup.

//greg//

 

[Rich Waugh]

If his Jinma 304 is like my 304, it would hurt a lot to expose the oil pump - requires splitting the tractor to drop the sump. I'd suggest draining out whatever oil is in it, remove the filter and get a new one. Drain the old filter and re-install. Fill the sump with about 7 quarts of diesel fuel, pull the compression release and lock it open and crank the engine for twenty seconds or so. Close the compression release and start it up, let it run for a half a minute and shut it down. If it sounds weird at all, shut it down immediately, of course.

After doing the above to flush the engine and oil passages, drain everything out , toss the old filter, install new filter and fill with 15W40 Diesel oil like Rotella T or equivalent. Start the engine and let itr idle a minute, watching the pressure gauge. Listen to it to see what it is telling you. Then shut it down and pull the dipstick. Check the level and top up if necessary. Observe the color of the oil on a white paper towel - is it slightly darker than the new oil? It should be, from having picked up a bit of the remaining oil old oil, though this may be hard to tell. Do you get good pressure now?

This is what I would do, others may have other advice.

 

[greg_g]

Sorry, didn't know that about a 304. Accessing mine only required removing the front driveshaft and dropping the bottom plate.

//greg//

 

[Rich Waugh]

My 304, which has, I should note, the TY395 engine, has a cast iron sump that is part of what the bell housing bolts to. And you can't access those bolts until the tractor is split at the clutch housing. No way to drop the sump without splitting tractor. Now, there may be a different configuration with the 4-cylinder engine, I don't know. Could be a difference from one year to the next, too. Mine is a 20007 model.

 

[bgarretson]

My 304, which has, I should note, the TY395 engine, has a cast iron sump that is part of what the bell housing bolts to. And you can't access those bolts until the tractor is split at the clutch housing. No way to drop the sump without splitting tractor. Now, there may be a different configuration with the 4-cylinder engine, I don't know. Could be a difference from one year to the next, too. Mine is a 20007 model.

I believe mine is a 2006 which has the Y480 engine in it. From doing further research and talking to a friend it sounds like it may be the oil pump. I'll do some more looking and try to pull it out of the field tomorrow to see if I can take the pan off with ease.
Thanks

 

[erj]

If it was me, I would follow the cheaper/easier suggestion that Rich made.
Flush the system and change the oil before looking further.
RonJ

 

[greg_g]

My 304, which has, I should note, the TY395 engine, has a cast iron sump that is part of what the bell housing bolts to.

Yeah, I was thinking the Y485. On that one the bottom of the oil sump is a removable plate.

//greg//

 

[quicksandfarmer]

I have a 354 with the Y485 engine, purchased February 2007. I replaced the oil pump this summer, you have to split the tractor to remove the oil pan, there is no access plate. Plus the front wheels bolt into the oil pan. You pretty much have to take the engine out altogether and suspend it, you can't jack from below with the pan off. It's a pretty big job, but it is doable with a few simple tools.

There are at least three types of oil pans for the Y485. In models meant for tractors (the Y485T) the oil pan is cast iron and provide structural support, it attaches to the transmission and the front end. It comes with and without an access plate. There is also a model meant for generators that has a stamped steel oil pan. The three types are not interchangeable, and each uses a slightly different gasket. Jinma being Jinma all three gaskets have the same part number so it took me a few tries to get the right one for my tractor. In the end what I did was take a picture and email it to Tommy at Affordable, he had someone walk around his gasket room until they found one that looked like the picture. Such is life in the Chinese parts business.

I always had low oil pressure at idle, I remember the very first time I got it warmed up the oil light came on at idle. One time by mistake I put a thinner oil in at an oil change and the oil pressure was quite low, it definitely needs 15w40.

Since I replaced the oil pump my pressure has been substantially higher at all RPM's. Like twice as high. I read somewhere that there has been a design change with the oil pump but I don't remember where.

When my oil pump failed the driveshaft sheared off, that seems to be the most common failure mode. When that happens you get zero oil pressure. It's easy to test for: take the oil filter off and put a bucket under the mount. Engage the compression release and spin the engine. If the pump is working at all you'll get oil coming out of the oil filter mount (unless your sump is dry, but I assume you already checked that).

If your oil pump is shot I can give you step-by-step instructions, I just finished doing the job. One thing I learned the hard way is there are three different models of oil pump used in these engines and they are not interchangeable. This page at Circle G describes the differences:
Complete Oil Pump Assembly-200

 

[greg_g]

There are at least three types of oil pans for the Y485. In models meant for tractors (the Y485T) the oil pan is cast iron and provide structural support, it attaches to the transmission and the front end. It comes with and without an access plate.

Well, the Y380/385 had 3 oil sump configurations, I didn't realize that the Y485 did as well. Mine was in a TaiShan 354. What you call an access plate was - on mine - the whole bottom of the cast iron sump. Drop the driveshaft, drop the plate, there's the oil pump.

//greg//