NL oil pressure

[Olly75]

So, my generator saga is continuing.

I ran it the other day to warm it thorough as it hadn't been run in a while with no problems.

A few days ago I started it again and it cut out as soon as I let go of the start switch. Checked oil and water etc and all is correct, so after some research disconnected the oil switch and started it up and it ran fine. Assuming the oil switch was bu**ered I changed it out but it still won't run without the override switch pressed.

Following the manual it says I should change the oil and filter to make sure the filter isn't clogged (last oil change was 15 hours ago). To change the oil I need to run the genertator 15 minutes to warm the oil through.

So the question is, if I run it and override/disconnect the oil pressure switch will this damage the engine, assuming it is a clogged filter, while its warming up?

[a64pilot]

Odds of it being a clogged filter are nearly zero, to begin with the filter or engine should have a bypass valve, clogged filters are not allowed to ruin engines, that would be very poor design. Often in very cold temps the oil filter is bypassed until the oil is thin enough to flow through, so filter bypassing isn’t rare.
Most often low oil pressure switches are normally open and close when there is pressure, so you should have to short the wires together to make it run, I’ve not seen one that opens when there is pressure, not saying it doesn’t just that I’ve not seen it.

If you really think it could be the filter, change it, you don’t have to change oil, and if you want to change oil do so. It’s best to change oil when it’s hot, but not mandatory.

However what I Would do is take the low oil pressure switch to an auto parts store and buy a cheap direct pressure gauge, you take the switch to ensure the kit the gauge comes with has the same thread, and if it doesn’t buy an adapter, most likely it will. Connect the direct pressure gauge and then run the motor, if the oil pressure is up to spec then you either have had two bad switches or more likely a wiring problem.
If it’s not up to spec, then call a mechanic, you don’t want to keep running this thing chasing your tail. Cause without pressure, yes you will ruin it.

Not to be insulting, but are you certain it has oil in it?

[Olly75]

Originally Posted by a64pilot

Odds of it being a clogged filter are nearly zero, to begin with the filter or engine should have a bypass valve, clogged filters are not allowed to ruin engines, that would be very poor design. Often in very cold temps the oil filter is bypassed until the oil is thin enough to flow through, so filter bypassing isn’t rare.
Most often low oil pressure switches are normally open and close when there is pressure, so you should have to short the wires together to make it run, I’ve not seen one that opens when there is pressure, not saying it doesn’t just that I’ve not seen it.

If you really think it could be the filter, change it, you don’t have to change oil, and if you want to change oil do so. It’s best to change oil when it’s hot, but not mandatory.

However what I Would do is take the low oil pressure switch to an auto parts store and buy a cheap direct pressure gauge, you take the switch to ensure the kit the gauge comes with has the same thread, and if it doesn’t buy an adapter, most likely it will. Connect the direct pressure gauge and then run the motor, if the oil pressure is up to spec then you either have had two bad switches or more likely a wiring problem.
If it’s not up to spec, then call a mechanic, you don’t want to keep running this thing chasing your tail. Cause without pressure, yes you will ruin it.

Not to be insulting, but are you certain it has oil in it?

Ha, I'll never be insulted! Yep the oil is topped up, unless the dip stick is lying

I'll get an oil pressure gauge and see if it reads anything.

I just checked the first switch with a multi meter (online tutorial and it does appear to be working)

[skipperpete]

Is it a NL673? If so, there’s a pressure control valve screwed into the block near the injector pump and cylinder head oil feed line are. Wise advice from a64pilot about not running it until you absolutely know if it has oil pressure.
The oil pump is a bit of a challenge to replace, its under the timing gear cover and pressed into the cylinder block..... and it’s aluminum so it has to be pressed in not whacked in.

[Wotname]

Originally Posted by a64pilot

.........
Most often low oil pressure switches are normally open and close when there is pressure, so you should have to short the wires together to make it run, I’ve not seen one that opens when there is pressure, not saying it doesn’t just that I’ve not seen it.
........

???
Maybe we have always looked at different engines but I have never seen a low oil pressure switch that has normally open contacts. All the low oil pressure switchs I have seen have normally closed contacts.

Normal in this sense is when the engine is static or at rest i.e. not running.

This is why the low oil pressure lamp illuminates after the key is ON and before the engine starts. The switch contacts are closed allowing the lamp to be illuminated. Once oil pressure is established, the switch contacts open and the lamp extinguishes.

If the switch was normally open, then a relay would be needed to illuminate the lamp when there was an absence of oil pressure.

[Olly75]

Originally Posted by skipperpete

Is it a NL673? If so, there’s a pressure control valve screwed into the block near the injector pump and cylinder head oil feed line are. Wise advice from a64pilot about not running it until you absolutely know if it has oil pressure.
The oil pump is a bit of a challenge to replace, its under the timing gear cover and pressed into the cylinder block..... and it’s aluminum so it has to be pressed in not whacked in.

It's an NL643. I've found the feed line for the cylinder block head (enters the head just behind the oil pressure switch) but doesnt look like there is a pressure control valve near it.

'A bit of a challenge to replace' assume that means it's a complete bu**er and involves the engine being out of the boat! I've had so many issues with it that pulling it out might not be the worst thing (trying to ignore the financial pain obvs) as I can then get it completely rebuilt giving me confidence in it long term...

[skipperpete]

Here’s the oil pressure regulator and its location, ya need a 24 mm socket and bar. The piston is at rest in the pic and uncovers the other holes as the pump output increases.
The first thing you need to do is verify the actual oil pressure before getting into deeper troubleshooting. Excellent engine in a legendary genset, well worth looking after.
Pete.

[skipperpete]

[Olly75]

Originally Posted by skipperpete

Here’s the oil pressure regulator and its location, ya need a 24 mm socket and bar. The piston is at rest in the pic and uncovers the other holes as the pump output increases.
The first thing you need to do is verify the actual oil pressure before getting into deeper troubleshooting. Excellent engine in a legendary genset, well worth looking after.
Pete.

Awesome, thank you. Ill see if I can borrow a pressure testing kit (can't buy one until lockdown is lifted here in a couple of weeks). Assuming the test shows no pressure is the next step to remove the oil pressure regulator and see if its stuck?

[a64pilot]

Originally Posted by Wotname

???
Maybe we have always looked at different engines but I have never seen a low oil pressure switch that has normally open contacts. All the low oil pressure switchs I have seen have normally closed contacts.

Normal in this sense is when the engine is static or at rest i.e. not running.

This is why the low oil pressure lamp illuminates after the key is ON and before the engine starts. The switch contacts are closed allowing the lamp to be illuminated. Once oil pressure is established, the switch contacts open and the lamp extinguishes.

If the switch was normally open, then a relay would be needed to illuminate the lamp when there was an absence of oil pressure.

Normal pressure switches used on cars and on our propulsion motors, your correct. That is why it’s important to look for the light and buzzer before you start cause that’s your continuity test, if a wire were to break or a terminal get loose etc, you lose your protection, so you listen for the buzzer and test the system before every start.
On Murphy switches ( a likely farmer name for protective switches) they are normally open and close upon getting pressure, that way instead of losing protection should a wire break or corrosion on a connection occur, the engine shuts down. Makes it fail safe, where a normally closed switch isn’t.

[Olly75]

To resurrect this thread, I've got hold of a mechanical pressure gauge for the oil and started the genny with it hooked up.

I'm getting a reading of around 5psi which to my inexperienced eye seems low, I cant find any mention in the manual of their recommended pressure, so would anyone have an idea?

[Wotname]

Originally Posted by Olly75

To resurrect this thread, I've got hold of a mechanical pressure gauge for the oil and started the genny with it hooked up.

I'm getting a reading of around 5psi which to my inexperienced eye seems low, I cant find any mention in the manual of their recommended pressure, so would anyone have an idea?

Sounds very low to me.
Was that hot or cold?
Either way, it sounds way low unless the engine is very hot, at idle and has lots of hours on it.

[kmacdonald]

Originally Posted by Wotname

???
Maybe we have always looked at different engines but I have never seen a low oil pressure switch that has normally open contacts. All the low oil pressure switchs I have seen have normally closed contacts.

Normal in this sense is when the engine is static or at rest i.e. not running.

This is why the low oil pressure lamp illuminates after the key is ON and before the engine starts. The switch contacts are closed allowing the lamp to be illuminated. Once oil pressure is established, the switch contacts open and the lamp extinguishes.

If the switch was normally open, then a relay would be needed to illuminate the lamp when there was an absence of oil pressure.

This is correct. Oil switches are normally closed and temp switches are normally open.

[kmacdonald]

Originally Posted by Olly75

To resurrect this thread, I've got hold of a mechanical pressure gauge for the oil and started the genny with it hooked up.

I'm getting a reading of around 5psi which to my inexperienced eye seems low, I cant find any mention in the manual of their recommended pressure, so would anyone have an idea?

That's way low. Dont run the engine. It should be about 60 psi at startup and 50 psi when hot. Tell us some engine history and work done on it.

[kmacdonald]

You dont need to run the engine 15 minutes before changing the oil. That just makes it easier or drains faster when warm. Is there water in the oil? Does it look milky? What base engine is it?