Oil & Fuel Oil Pressure After New Pump??? Jinma 284

[Bob Rooks]

See what I mean? Wasted energy. He and I have been down this road before. He's a pro at trolling.

 

[buickanddeere]

See what I mean? Wasted energy. He and I have been down this road before. He's a pro at trolling.

Explains why there is more interest in fighting than there is in engineering facts. Some people would be offended if I stated the sun rises in the east and sets in the west.

 

[Bob Rooks]

Hmm. I'm an engineer. And you?

 

[boomer1025]

62 replys and no one has ask the million dollar question.
Did the engine start loosing oil pressure over time, or did it start all at once ??

 

[quicksandfarmer]

62 replys and no one has ask the million dollar question.
Did the engine start loosing oil pressure over time, or did it start all at once ??

OP said he bought the tractor with 300+ hours on it, it always was low.

My experience, repeated from a few pages back: I have a very similar tractor with a very similar engine. It had low oil pressure, especially when warm, from the day the dealer delivered it brand new. I replaced the oil pump a few years ago and pressure has been much higher ever since.

 

[SPYDERLK]

Then you didnt need to replace the pump. ... Your engine has some loose clearances on the crank, Id guess. Is the reason you replaced, because you noticed you were running lower oil pressure than when it was newer?

Have you been using the same weight oil from the beginning? What was your hot pressure when the tractor was newer?

62 replys and no one has ask the million dollar question.
Did the engine start loosing oil pressure over time, or did it start all at once ??

,,,,,,,,,,,,,,,Thatll be $2M please.

 

[Bob Rooks]

62 replys and no one has ask the million dollar question.
Did the engine start loosing oil pressure over time, or did it start all at once ??

That question has been asked.

 

[Bob Rooks]

FWIW.
This is a Chinese oil pressure gauge.



These are Murphy Swichgages connected to an alarm system that I installed on the excavator. It has a Mitsubishi 4K (40 hp) diesel engine with 1,296 hours on it. It is idling at operating temperature.

 

[duttymaxx]

After pricing main bearings and visiting with a buddy, I believe this is something we are going to tackle towards the end of September, I do believe it has to be the root of the problem hopefully..... If not we'll have a couple 3 or 4 hours of work tied up in it and about $150 in parts, after going through 3 gauges, 1 factory 2 different sending units and 2 mechanicle gauges I'm at a loss as what to do other than start tearing it down and replacing bearings. I certainly do appreciate everyone's replies even the troll and his far fetched ideas.

 

[SPYDERLK]

I have a Jinma 354, which has the 485 engine, which is the same as the 385 engine you have except it has four cylinders to your three. Many of the parts interchange, including the oil pump. I remember the first day I got it --brand new from the dealer-- I used it for a while, and when it was good and warm I slowed the engine down to idle and the oil light came on. I would always get low oil pressure when engine was warm, with the pressure tracking RPM's. I just dealt with it by never letting the engine idle. A couple of years ago the oil pump failed and I replaced it, and all of the sudden I had much better oil pressure at all speeds and temperatures. At that time I read that the oil pump had been redesigned because of problems with it. So is it possible you got an old stock oil pump?

I'll add an anecdote that may or may not be helpful: one time I changed the oil, and I miscalculated how much oil I needed and came up a quart short. It's a fairly long drive for me to anywhere that sells diesel oil, and I had work to do, so I just put in a quart of whatever the convenience store had, probably 10w40 or similar. I figured there's so much in the sump that a little wouldn't hurt. I had dramatically lower oil pressure, and I ended up draining all of the oil and replacing it with Delvac. The moral is that the pump used in the Jinma is very sensitive to oil viscocity -- which is why pressure drops so much when the oil warms up.

No continuity there. It must be .02 and .04mpa (20 and 40 kilo Pascals) ~ 3 and 6PSI. Sounds like pressure has always been low. Also, based on quicksandfarmer experience it appears there is a higher volume pump available ... or else one having tighter rotor clearance hence much less internal leakage.

OP said he bought the tractor with 300+ hours on it, it always was low.

My experience, repeated from a few pages back: I have a very similar tractor with a very similar engine. It had low oil pressure, especially when warm, from the day the dealer delivered it brand new. I replaced the oil pump a few years ago and pressure has been much higher ever since.

After pricing main bearings and visiting with a buddy, I believe this is something we are going to tackle towards the end of September, I do believe it has to be the root of the problem hopefully..... If not we'll have a couple 3 or 4 hours of work tied up in it and about $150 in parts, after going through 3 gauges, 1 factory 2 different sending units and 2 mechanicle gauges I'm at a loss as what to do other than start tearing it down and replacing bearings. I certainly do appreciate everyone's replies even the troll and his far fetched ideas.

,,,,,,,,,,,,,,,,,,,,,,It appears you have discounted quicksandfarmer posts. ... And your own :

Sorry for the delay. The pump was replaced due to the oil pressure being low after the engine warmed to operating temp 180-200degrees. It Would start out around 50psi the gradually drop to around 10psi. There is no abnormal sounds coming from the motor. When the oil pan was dropped there was very very minimal amount of metal shavings least non that caused any concern to me nor was there any type of trash or sludge buildup. The new replacement pump was a spot on match to the old one, so with that you could out the bolts bottoming out in the pan. Just for to rule out a bad gauge I went and got second mechanical gauge and swapped them out. Oil pressure at startup now is around 10 psi and running the tractor around 1600/1800rpms I'll see 25psi, but it will gradually drop to around 10 once the motor gets good and warmed up. I hope I answered most of the questions posted.

 

[buickanddeere]

Could consider measuring the journals and bearings with a mic plus using plastic gauge to obtain before and after numbers. If the journals are out of round a session on the crank grinder will be required.
Could be cam bearings bleeding the pressure away as bad or worse than main & rod bearings.

 

[SPYDERLK]

Could consider measuring the journals and bearings with a mic plus using plastic gauge to obtain before and after numbers. If the journals are out of round a session on the crank grinder will be required.
Could be cam bearings bleeding the pressure away as bad or worse than main & rod bearings.

Based on what I see from the OP and quicksandfarmer Im betting on design defect in the oil pump that results in a lot of internal bypass - esp as engine warms and oil viscosity decreases. This effectively decreases pump delivery and hence oil pressure. Jinma seems to have corrected this [quietly] from the experience relayed by qsf in his posts. ... OP sees no indication of damage. No doubt that engine has been on the edge, but with just a verified upgraded pump it will probably be happy for a long time.

 

[buickanddeere]

The replacement oil pump , was it still the old style or the new style ? Would be worthwhile to take a new pump apart and measure at least the width of the gears or rotor and the width of the pump body? Then mill the pump body narrower if required ?

 

[SPYDERLK]

Yes. Custom work like that could eliminate excessive end clearance between the ends of the pump casing and the rotor/gerotor(?) assembly. One would need documentation or experience to make correct choices, as well as a way of doing or getting what you want done. ... And is that what the factory did for the result quicksandfarmer experienced. -- There may be a larger working element hidden inside the same casting - no new mold necessary. Perhaps a shim left out, added, or changed. OEM knowledge is needed ... maybe even privileged info they dont want to spread. Absent that, or w/o parts to compare we are stuck with an alerting oil pressure situation that looks systemic prior to the iteration apparent from QSFs pump change.

 

[Bob Rooks]

The Y385 oil pump appears to be the gerotor style, and looks to have a built in adjustable by-pass valve.

 

[SPYDERLK]

The Y385 oil pump appears to be the gerotor style, and looks to have a built in adjustable by-pass valve.
View attachment 479263

Thanks, do you have any OEM connections? That looks tiny.

,,,,,,, Valve bypass is not an issue at reported pressures - unless its faulty and just seeps constantly.

 

[Bob Rooks]

Thanks, do you have any OEM connections? That looks tiny.

,,,,,,, Valve bypass is not an issue at reported pressures - unless its faulty and just seeps constantly.

Yeah, not very big, and it runs submerged so doubtful of any suction leaks. So there is two by-pass valves involved - one at the pump and one at the filter head. That pic is from Circle G Tractor's online parts book. I have no OEM connections. Just speculating that the local by-pass valve could be the culprit. The Chinese have a bad habit of updating parts without updating part numbers so there is no guarantee of what you are getting.

 

[Bob Rooks]

I think the OP needs to have another look at his new pump as there may have been modifications or changes in the by-pass valve.

 

[duttymaxx]

I think the OP needs to have another look at his new pump as there may have been modifications or changes in the by-pass valve.

I looked at my old pump today and actually broke it down, it's sad that on startup before I replaced the pump I had more pressure than what I have now. I guess it's possible that the internal bypass may not be adjusted properly on my new pump. I'm thinking whenever I drop the oil pan I'll replace the impeller and pump body with the old one.

Other than excessive metal shavings is there any other telltale signs that the main bearings are bad?

 

[Bob Rooks]

For one thing, you shouldn't have any metal shavings at all. None. Time to start digging.