Failed oil pump on my Yanmar 4JH3-HTE?

[tudorsailor]

I have a Yanmar 4JH3-HTE installed 2001. It has done 6000 hours. It is not particularly noisy or smoky. It has been serviced annually and filled with Yanmar oil
Last year the oil pressure gauge stopped reading and the local team put in a gauge from another boat and the pressure then read normally.
This year, my wife commented that the red oil pressure warning light was staying on longer after starting the engine than normal. It does go out, but sometimes only after a minute
I then noticed that the pressure gauge was reading maximum as soon as the engine was given 12v and before it was actually running. I assumed that the gauge was faulty

The boat is now in Murter Croatia where there is an authorised Yanmar mechanic
He installed a new Yanmar Pressure sender. It registered no oil pressure. He checked by grounding etc that the gauge and wire was OK
He then measured the oil pressure with a mechanical gauge and it was unrecordable both at the hole for the pressure sensor and then also at the hole for the pressure switch that activates the red warning light. He double checked with another mechanical pressure gauge, still unrecordable

He then removed the block that is under the oil filter (with great difficulty as the screws were stuck) to checked the pressure relief valve. He found no problems
He put everything back together and the oil pressure dial still read zero and then when rev'd the engine to over 3000 rpm - which is not something I ever do - the red oil pressure warning light came on

So it seems that there really is minimal oil pressure.
The engineer's opinion by a process of elimination is that the oil pump has failed. He plans to remove the engine and fix whatever is necessary. Obviously not a minor thing

Are there any other possibilities that he has not thought of for low/no oil pressure?
When the engine is on the bench what things should I expect him to do to "recondition" the engine? I did ask about the crankshaft and he said he would replace the bearings if necessary.

All rather stressful.................
Tudorsailor

 

[fredrussell]

Easy way to check if pump is faulty is to remove pressure sender and turn engine over. If pump is working oil will come spewing out the hole. I would definitely want bearings and crankshaft journals checked - it sounds like engine has been run in its current ‘oil-less’ (?) state enough to warrant checking.

 

[Boater Sam]

Pick up strainer in the sump blocked with sludge?
There must be some oil flow else the bearings would have run by now.
Very unlikely that the oil pump is at fault I would think.

 

[tudorsailor]

Pick up strainer in the sump blocked with sludge?
There must be some oil flow else the bearings would have run by now.
Very unlikely that the oil pump is at fault I would think.

Can one clean the pick up strainer in the sump without removing the engine?
TS

 

[penberth3]

Easy way to check if pump is faulty is to remove pressure sender and turn engine over. If pump is working oil will come spewing out the hole. I would definitely want bearings and crankshaft journals checked - it sounds like engine has been run in its current ‘oil-less’ (?) state enough to warrant checking.

That's something I picked up on. A lot of trial running with a defective oil pump, not a great idea.

 

[Boater Sam]

Can one clean the pick up strainer in the sump without removing the engine?
TS

I would doubt it. It may be worth using compressed air in through the oil switch hole in the hope that it will pass enough pressure through the pump into the strainer and clear some of the clag.

Or even pump in diesel fuel through the same hole under a lot of pressure. Then drain it off of course. It will go everywhere, bearings, cam, pump and strainer into the sump. Can't do any harm providing you drain it.

We used to get this problem with old American V8s where they ran cold on short trips and sludged up.

From your description of varying intermittent pressures prior to losing almost all pressure I would be very doubtful that it is a mechanical fault with the pump itself.

 

[billskip]

It may be worth using compressed air in through the oil switch hole in the hope that it will pass enough pressure through the pump into the strainer and clear some of the clag.

What about the non return valve, wouldn't it prevent reverse pressure?

 

[Boater Sam]

What about the non return valve, wouldn't it prevent reverse pressure?

What non return valve? Never seen one in an oil way of an engine. Pressure over release valve yes, filter blocked bypass valve in the can, yes.

 

[billskip]

What non return valve? Never seen one in an oil way of an engine. Pressure over release valve yes, filter blocked bypass valve in the can, yes.

Hmmm...if the oil pump drains back into the sump (if it's a lifting pump and not a flooded suction pump) normally the pump has a spring and ball which opens under suction and closes to prevent oil drain back to the sump....but maybe you know best.....

 

[Boater Sam]

Hmmm...if the oil pump drains back into the sump (if it's a lifting pump and not a flooded suction pump) normally the pump has a spring and ball which opens under suction and closes to prevent oil drain back to the sump....but maybe you know best.....

There's sarky.

Every engine oil pump I has seen is in the sump with a short pickup tube and strainer. We are not talking dry sumps and scavenge pumps here surely?

 

[billskip]

There's sarky.

Every engine oil pump I has seen is in the sump with a short pickup tube and strainer. We are not talking dry sumps and scavenge pumps here surely?

Nothing sarky at all, maybe you know best, take it as a compliment...
I think you will find reference to non return valves fitted to engines.

 

[Boater Sam]

Nothing sarky at all, maybe you know best, take it as a compliment...
I think you will find reference to non return valves fitted to engines.

Well, I googled "non return valves fitted to engines" and all I found were fuel non return valves.
Can you give me an example of a wet sump engine, diesel or petrol ( or paraffin coming to that ) that has such a valve in the lubrication oil line please?

 

[billskip]

Well, I googled "non return valves fitted to engines" and all I found were fuel non return valves.
Can you give me an example of a wet sump engine, diesel or petrol ( or paraffin coming to that ) that has such a valve in the lubrication oil line please?

 

[penberth3]

Well, I googled "non return valves fitted to engines" and all I found were fuel non return valves.
Can you give me an example of a wet sump engine, diesel or petrol ( or paraffin coming to that ) that has such a valve in the lubrication oil line please?

Don't some oil filters have a non-return valve inside them?

 

[Boater Sam]

Don't some oil filters have a non-return valve inside them?

Many have anti drain back rubber flaps, all have bypass if blocked valves. Neither would affect my suggestion of injecting air/fuel into the oilway to backflush the strainer.

 

[Boater Sam]

View attachment 158682

VW has only non return in the tappet feed as it has hydraulic lifters, Not many stationary antique CS Listers in narrow boats I bet!

 

[billskip]

VW has only non return in the tappet feed as it has hydraulic lifters, Not many stationary antique CS Listers in narrow boats I bet!

That was from a quick search...not limited to only those engines.....there are others...but this thread is surely about the OP's problem....if a restricted return in the oil line is fitted to prevent drain back,(and I dont know with this particular engine) could that be a problem ....

 

[tudorsailor]

Thanks for everyone's input.
With regard to trying to back flush..........if this cleared a blockage and the pressure went up, wouldn't there be a risk that the blockage would re-occur unless one removed the pump and sump to clean it. This still entails removing the engine ?
TS

 

[rogerthebodger]

Most engine oil pumps are positive displacement pump being lobe pumps

So do not need non return valves as back flow is not possible.

The also means back flushing is also not possible unless the pump is turned backwards

Buy Oil Pump 129900-32001 for Yanmar Engine 4TNE98 4TNV98 4TNE94 4TNV94L | eBay

 

[penberth3]

Thanks for everyone's input.
With regard to trying to back flush..........if this cleared a blockage and the pressure went up, wouldn't there be a risk that the blockage would re-occur unless one removed the pump and sump to clean it. This still entails removing the engine ?
TS

Good point. Unless you're doing a complete strip down and a proper clean, sludge and crap is best left undisturbed.