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

[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.