NL oil pressure

[kmacdonald]

If it a kubota engine this is your problem.
https://youtu.be/XO-jhkjpTpc
An aluminum plug at the end of the camshaft pops out. Watch the video. I'm not sure what base engine NL uses for that generator so I could be wrong but if it does use that engine then this is the problem. Faily easy fix.

[Olly75]

@wotname, it was from a cold start, there was no load on it and she's only had (allegedly) 540 hours running time.

@kmacdonald, Ive found a refernce to oil pressure on the web and its supposed to be 15psi at idle and rising under load, so still way too low... I dont know what NL used as the original engine block and can find no number (that makes any sense) stamped into the block.

I will try removing and cleaning the oil pressure regulator as suggested by Skipperpete tomorrow.

Ive looked at the video you posted, and although simple, its beyond me to attempt that fix in the boat!

Many thanks for the responses.

[Wotname]

Originally Posted by Olly75

@wotname, it was from a cold start, there was no load on it and she's only had (allegedly) 540 hours running time.

@kmacdonald, Ive found a refernce to oil pressure on the web and its supposed to be 15psi at idle and rising under load, so still way too low... I dont know what NL used as the original engine block and can find no number (that makes any sense) stamped into the block.

I will try removing and cleaning the oil pressure regulator as suggested by Skipperpete tomorrow.

Ive looked at the video you posted, and although simple, its beyond me to attempt that fix in the boat!

Many thanks for the responses.

Yep, 5 psi cold on low hour engine is manifestly low. Let's hope it is only some foreign muck stuck in the oil pressure relief valve.

[skipperpete]

Originally Posted by Olly75

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?

The engine that NL uses is a Shibaura and the specific model is defined by the bore size - 67 mm and the number of cylinders-3. The oil pressure range in the service manual is 43psi to 71psi so you need to check that pressure regulating valve. If the valve is the problem it will either be stuck wide open and showing daylight through both pairs of the relief holes or possibly the spring is broken and letting the plunger go to the bottom of the bore. Have you changed the oil filter recently? It could cause a problem if it’s not a compatible filter.
Avoid anything but the very briefest of test runs while troubleshooting the lack of oil pressure or you may/will damage the crankshaft bearings and other parts.
Cheers, Pete.

[skipperpete]

Oops, 64mm bore. It’s also called a Perkins 103-6.

[Olly75]

I changed the filter and oil about 15 hours ago, using a filter that I bought in polynesia, thats off brand but to the exact spec as the NL versions.

Ive now removed the oil pressure plug and attahced a picture, looks to me (based on the image the Skipperpete posted previously) that its normal, but please advise otherwise!

So assuming that the pressure valve is normal, what would be the next thing to check? Or am I at the stage of getting the front off to have a look at the oil pressure pump?

[a64pilot]

Originally Posted by kmacdonald

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

Oil switches that illuminate a light yes, but not ones that shut down engines. Those are open with no pressure, that way they are fail safe, cause if they were closed then the motor would run with a broken wire or loose connection even with no pressure.
Although either can be used a normally closed oil pressure switch is not fail safe.

[a64pilot]

Originally Posted by Olly75

I changed the filter and oil about 15 hours ago, using a filter that I bought in polynesia, thats off brand but to the exact spec as the NL versions.

Ive now removed the oil pressure plug and attahced a picture, looks to me (based on the image the Skipperpete posted previously) that its normal, but please advise otherwise!

So assuming that the pressure valve is normal, what would be the next thing to check? Or am I at the stage of getting the front off to have a look at the oil pressure pump?

I’m not familiar with that oil pressure relief valve, but it looks like the inside should move and have spring resistance, if so that means it’s not stuck open.

However before going any further I’d change that off brand oil filter to a known quality filter. Can’t hurt and I have seen filters rarely cause low oil pressure. Do the simple easy, cheap things first. Don’t run her long at 5 PSI though.

Remember this engine doesn’t ever idle, it’s always at operating RPM, I’d like to see ten times the pressure your getting. As a reference my Yanmar runs at just under 65 lbs not or cold at Cruise.

[Lepke]

Besides worn bearings, worn oil pump, or low oil, the most common cause of low oil pressure is the pressure relief valve spring. When a cold engine starts, the oil is thick and makes a higher pressure. The spring compresses, allowing the pressure relief valve to open and divert some of the oil back to the pan. With age the spring gets weak, but I've never seen one weak enough for 5psi. I'd say the spring is broken or the valve has a piece of debris stuck, jamming it open.

[kmacdonald]

How much is a new pressure valve? Start cheap. Add pain slowly.

[kmacdonald]

Originally Posted by a64pilot

Oil switches that illuminate a light yes, but not ones that shut down engines. Those are open with no pressure, that way they are fail safe, cause if they were closed then the motor would run with a broken wire or loose connection even with no pressure.
Although either can be used a normally closed oil pressure switch is not fail safe.

Those would only be used on unattended commercial engines. You wouldn't want a plane shutting down the engines for low oil pressure. I guess a generator might have one since shutting down would only drop electric power. Propulsion engines wouldn't. Fail safe definitely isn't a requirement for marine engines. That's more of an aviation thing for obvious reasons but it comes at a price

[a64pilot]

If it ain’t stuck open, it’s not the relief valve, and even stuck open I’d be amazed to only see 5 PSI, the people who design these things aren’t stupid and I’d be amazed if they had a relief valve that could dump all the way down to 5 PSI, especially with cold oil.

However many engines rely on filter having a plugged filter bypass valve, and not all filters do, most filters also have an anti drain back valve, but not all do, especially when you get to unknown quality filters there may be missing parts, because not all filters are required have anti drain back or bypass valves.
https://www.pgfilters.com/tech-tips/...ve-oil-filter/

Before you go removing the generator and or tearing into its internals, try another filter, don’t need change the oil, just screw on a new quality filter. It’s rare, but have seen it before.

Most filters don’t swell and burst with a defective bypass filter, only ones I have ever heard of were Duramax Diesels and only then when they ran off brand filters, because a Diramax when cold would go over 100 PSI and I think the early models ran 80 PSI of so even hot.

[a64pilot]

Originally Posted by kmacdonald

Those would only be used on unattended commercial engines. You wouldn't want a plane shutting down the engines for low oil pressure. I guess a generator might have one since shutting down would only drop electric power. Propulsion engines wouldn't. Fail safe definitely isn't a requirement for marine engines. That's more of an aviation thing for obvious reasons but it comes at a price

Yes, we are talking about generators and other unattended engines, like irrigation systems etc. Farmers call these switches “Murphy” switches cause of course they protect against Murphy, I believe that name may even be a real manufacturer now, seems it has been for a long time.

Art Murphy opened the doors of Murphy Safety Switch of California in Los Alamitos, California to Distribute the entire line of FW Murphy Safety Switches, Control Panels, and Automation Devices to the Oil and Irrigation Operations in the West

No aircraft that I know of will shut down to low oil pressure high temps or anything else, many will have torque and ITT limiters though and keep you from blowing one up unintentionally, but they just stop adding fuel when a set limit is reached or exceeded.

[skipperpete]

I agree 100% with a64pilot and would add that this might be one of those times where I would actually fill the spin on with oil and accept a bit of spillage when installing it.

[Compass790]

How many hours on the engine? Sorry if it's been posted & I missed it but I'd be checking oil pump tolerances after other tips by previous posters if it's a high hours engine.