NL oil pressure

[Compass790]

Originally Posted by kmacdonald

Did you have to adjust the valve lash a lot or was it close? I have never seen or heard of a confirmed oil pump failure even on high hour engines. The oil doesn't have a diesel smell to it does it? Did you adjust the valves as preventative maintenance or to correct an issue?

Check out this thread:https://www.cruisersforum.com/forums...-199240-2.html

I know of 3 owners at least who have had oil pump failures with YS series Yanmars. They aren't catastrophic in general just that the rotor wears down into the housing so increasing the end plate clearance to the point where the pressure drops. The thread I posted was to another problem but it's just an illustration of what can happen.

[skipperpete]

The only thing that can go wrong with the valve lash adjustment is if the gasket breaks or is out of position and it can have serious consequences because the rocker cover is also the intake manifold and if the gasket is compromised the engine oil can get into the intake side. Normally this only leads to heavy oil consumption but the danger time is when doing an oil change and the rocker cover fill allows the oil level to rise and the overflow goes into the intake valves and can lead to a hydraulic lock in whichever cylinder had an open intake valve.
The low oil pressure could have been a problem for a long long time because the shutdown switch only triggers at below 5 psi and you normally have no way to see the actual pressure........ until now!
Respectfully, I have to ask if your recently acquired pressure gauge actually does read Psi and not kg/sq cm or Bar ?
I reassembled a Perkins Perama 103-06 that was showing a low oil pressure light, the owner and a couple of yachties stripped the engine down after or during a wine tasting event and later got me to reassemble it with a new oilpump........ it ran well after reassembly but , here’s the thing..... the old pump showed no sign of wear or damage and I’ve often wondered why it had only 4psi from an undamaged pump. ( the perk. 103-06 is the same engine as your NL643).
Cheers, Pete.

[Olly75]

Originally Posted by skipperpete

The only thing that can go wrong with the valve lash adjustment is if the gasket breaks or is out of position and it can have serious consequences because the rocker cover is also the intake manifold and if the gasket is compromised the engine oil can get into the intake side. Normally this only leads to heavy oil consumption but the danger time is when doing an oil change and the rocker cover fill allows the oil level to rise and the overflow goes into the intake valves and can lead to a hydraulic lock in whichever cylinder had an open intake valve.
The low oil pressure could have been a problem for a long long time because the shutdown switch only triggers at below 5 psi and you normally have no way to see the actual pressure........ until now!
Respectfully, I have to ask if your recently acquired pressure gauge actually does read Psi and not kg/sq cm or Bar ?
I reassembled a Perkins Perama 103-06 that was showing a low oil pressure light, the owner and a couple of yachties stripped the engine down after or during a wine tasting event and later got me to reassemble it with a new oilpump........ it ran well after reassembly but , here’s the thing..... the old pump showed no sign of wear or damage and I’ve often wondered why it had only 4psi from an undamaged pump. ( the perk. 103-06 is the same engine as your NL643).
Cheers, Pete.

Ha, yes the gauge reads both psi and kg/cm3, and Im definitely giving the psi reading!

Is there anything else I can test/check? If not and the next step is taking the front off the engine to have a look at the oil pump I'm not going to tackle it myself, will hunt for a local pro.

[skipperpete]

The only other thing that I can think of is the oil feed pipe from the block to the cylinder head, if it was partially blocked..... or there was a free unrestricted flow of oil out of the rocker gear for some obscure reason that could give you the 5psi reading.
The front cover removal starts with the injector pump, the rack control link needs to be un pinned with the pump lifted up.
The next hurdle is the crankshaft pulley, you need a damn tough little puller to pop that pulley off..... and watch out for the key, it’s only a small square of steel. Buy the gasket before you start[emoji4]

[Compass790]

Don't know the oil plumbing system on that engine but if there is a way to blow back down the suction feed side of the oil pump I'd do that when you check the oil pump. Some engines have a gauze strainer on the pickup tube & they can get clogged. Not normally on a low hours motor but possible.
The oil pump is most likely to be ok with those low hours but it has to be eliminated from the equation.
Ask the mechanic to bring his own pressure gauge to check as well. I mean he should do anyway but...

[kmacdonald]

This really isn't making sense for a 500 hour engine. I'm still inclined to believe the oil pressure sensor is in the wrong place. See if you can find a schematic showing the location of sensors.

[Wotname]

It doesn't even make sense for 5,000 hour engine for that matter!

I am intrigued by this fault and look forward to hearing about the root cause whenever it is discovered.

All the likely suspects have been looked at and cleared so that only leaves the most unlikely possibilities.

One has to assume it had good oil pressure sometime previously.

It would be nice if if the problem is simply an incorrect reading (for whatever reasons).

Weird......

[Olly75]

Originally Posted by kmacdonald

This really isn't making sense for a 500 hour engine. I'm still inclined to believe the oil pressure sensor is in the wrong place. See if you can find a schematic showing the location of sensors.

I followed the schematic, I have an oil pressure switch sensor and an oil pressure sender unit both located on the genny as per the diagram in their workshop manual.

Now the bit where I might have gone wrong.... I unscrewed the oil pressure switch and replaced it with a new one thinking it might not be working correctly. When the generator still shut down I removed the new switch and attached the mechanical oil pressure gauge in its place. I hoping this is the right place for it!

[a64pilot]

No, installing the gauge where the switch goes is the right place.
However again not very likely, but it is barely possible that oil galley is clogged with something, leave the gauge out and crank it over to see if it blows oil out strongly, have a few rags there as it may make a mess. It won’t start if you leave the switch wires disconnected. Hoping some sludge may be in there etc.
Out of curiosity what did you do to those wires to make it run, leave them disconnected or hook them together?

I have had oil pressure sending units clog a few times as they often have a restricted orifice so that if one blew the engine would only slowly leak and not blow out all its oil suddenly.

Truthfully I’m at a loss to explain it

[a64pilot]

Originally Posted by Olly75

I followed the schematic, I have an oil pressure switch sensor and an oil pressure sender unit both located on the genny as per the diagram in their workshop manual.

Now the bit where I might have gone wrong.... I unscrewed the oil pressure switch and replaced it with a new one thinking it might not be working correctly. When the generator still shut down I removed the new switch and attached the mechanical oil pressure gauge in its place. I hoping this is the right place for it!

If it has a sending unit, then it’s plumbed if you will for a gauge.
You could remove the sending unit and plug your gauge into there, if it’s a different place on the engine that ought to shoot down the clogged oil galley theory.

[Olly75]

The sending unit is tee'd off the same joint as the pressure switch unfortunately.

Just removed the pressure switch and cranked it, and once running there was a significant flow of oil so looks like the line isn't plugged.

The pressure switch is a single wire switch, that when wired up wont let the genny start because of the low oil pressure, but when detached the genny will start. If that makes sense...

[a64pilot]

Originally Posted by Olly75

The sending unit is tee'd off the same joint as the pressure switch unfortunately.

Just removed the pressure switch and cranked it, and once running there was a significant flow of oil so looks like the line isn't plugged.

The pressure switch is a single wire switch, that when wired up wont let the genny start because of the low oil pressure, but when detached the genny will start. If that makes sense...

Sure does, it’s a normally closed switch and is using the generator as a ground return so one wire.

[a64pilot]

Unless you have good access I think at this stage I’d pull the generator.
But then I don’t have good access

[Wotname]

Originally Posted by Olly75

........

The pressure switch is a single wire switch, that when wired up wont let the genny start because of the low oil pressure, but when detached the genny will start. If that makes sense...

Whoa - that doesn't make sense.

If wired correctly, the genny will start with zero oil pressure but if running it should stop if the oil pressure drops to low.

[Olly75]

Originally Posted by Wotname

Whoa - that doesn't make sense.

If wired correctly, the genny will start with zero oil pressure but if running it should stop if the oil pressure drops to low.

When the oil pressure switch is wired up if I hold down the preheat and shutdown bypass the genny will start and stay running, if I let it go the genny automatically stops. However when the oil pressure switch is disconnected the genny will continue running when I let go the preheat switch.