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Old 08-18-2022, 09:11 AM   #1
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Genset slow loss of oil pressure and shutdown

I have a Northern Lights 673 15KW genset (2006) that has been very reliable. However on a recent cruise it shut down. I checked the usual suspects such as the strainer and oil and all good. Did not seem like fuel starvation as it never stumbled. Just shut down as if turning off a switch. It restarted fine and ran for about 30 minutes before shutting down again. I only have gauges in the room so I cranked it up and watched the gauges. Normal readings but after 15-20 minutes oil pressure started dropping. It was so slow the gauge movement was barely perceptable. But over a period of 10-15 minutes it would get down below 20psi at which the low oil pressure switch would shut it down. FYI it had a fairly recent oil filter change in last 25 hours and had been running fine for over 2 years now.

Any ideas? I do plan to call NL and see if they have suggestions.
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Old 08-18-2022, 09:38 AM   #2
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I would start with changing oil filter.
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Old 08-18-2022, 09:49 AM   #3
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The good news is that the low oil pressure shutdown switch is working
properly. Steve's suggestion above is a good place to start.
The replacement should be the factory branded correct filter as well.

There are three or four things that can cause low oil pressure. The most
obvious is wear causing increased clearances that reduce oil pressure as the
oil warms up. How many hours on the plant?
Another possible cause is the oil pump itself or some crud blocking the pickup.
There also may be an oil pressure relief valve that may be opening at too
low a pressure as the oil warms up.
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Old 08-18-2022, 10:06 AM   #4
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What type of oil are you using? You may have diesel mixing with the oil which would cause a loss of viscosity when your heats. Maybe having a oil sample tested would be a good move and an oil and filter change would be recommend. Is your engine running hotter due to a failing impeller?
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Old 08-18-2022, 10:24 AM   #5
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FIRST thing I'd do is get a test kit and send off a sample of the oil to be tested. Don't use the genny until you have a read on that oil sample.

An interim quick and dirty test while waiting for the lab results: Take a drop of your oil from the dipstick (cold engine) onto a hard surface like a mirror alongside a drop of same oil out of you spare oil container and watch for abnormal spreading of the oil from the engine due to fuel dilution

Maybe the oil pressure sensor is bad.

You said oil was OK, but does that mean you noticed no change in level, like a rise? Are you checking it carefully? Does it smell like diesel.
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Old 08-18-2022, 10:30 AM   #6
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KISS, change the filter, then the oil & filter before taking the engine apart. If he pressure is good for 30 minutes then it is less likely other causes.
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Old 08-18-2022, 10:45 AM   #7
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Start with what you most recently serviced. You indicate that you recently changed oil so I'd start there. Check the viscosity grade and specification (API Performance level) of the oil you used. Oil thins as it heats up (which is normal), if the viscosity grade is lower than the engine specified then it exhibit this behavior. For example moving from a 15W-40 to a 10W-30 would reduce oil pressure. Similarly if you move from an SAE 30 to an SAE 10W-30 at temperatures below 100C the oil will be less viscous. I run 15W-40 in my NL genset (when it deigns to keep running but that's another story) with no issues. Keep in mind that it may not have done this immediately after the oil change since most multigrade oils thin a small amount due to shear thinning of the viscosity modifier. This effect is very small but if you were just at a critical point it could become relevant (normally it is irrelevant).

Others have mentioned oil filters. Most engines incorporate a high pressure bypass located in the filter. While these are designed to prevent over pressure if the bypass were stuck open then it could have a small effect on oil pressure. It would also mean you're not filtering. Fuel dilution is also mentioned. That could be a factor. Dirty injectors, improper opening pressure, and other issues can cause fuel dilution. However these are often accompanied by other symptoms such as smoke, uneven running etc. You might pull a sample of the oil and keep it should simpler solutions not work.

If it were me I'd change the oil/filter using a good quality diesel oil. NL recommends either 15W-40 or SAE 30 diesel engine oils. Lower viscosities are recommended only for below freezing temperatures. If the problem returns then check for fuel dilution in that sample you kept keeping in mind small amounts (1% -2%) are not unusual. You can send it to an oil analysis lab, but as I said, that's not where I'd start.
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Old 08-18-2022, 12:01 PM   #8
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Another thing to check is oil temperature. High oil temperature will produce low oil pressure.
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Old 08-18-2022, 12:02 PM   #9
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Good suggestions so far

Send off An oil sample

Change oil and filter being sure to use a CD or equivalent 10-40 oil. Donít use SJ or any ďsĒ oil. And use a NL branded filter.

The fact that your gauge shows a slow drop, then the safety switch activates makes it pretty clear that you have actual low pressure, not a gauge issue since those are completely independent devices, and both agree.

Can you say for certain that the oil pressure hasnít been dropping for some time as the engine warms up? Could it have been doing this for a long time, and only now gets low enough to cause a shutdown? If this came on progressively then itís seems likely that itís an excessive wear issue. But if it can on suddenly, a bad bypass valve or defective filter seems more likely.
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Old 08-18-2022, 03:59 PM   #10
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Quote:
Originally Posted by KnotYet View Post
.
The replacement should be the factory branded correct filter as well.
.
I'll just point out that engine manufacturers do not make oil filters.
All factory branded parts do is cost more.

But agree, filter and new oil is the place to start
As long as it meets spec.
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Old 08-18-2022, 05:25 PM   #11
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Quote:
Originally Posted by Simi 60 View Post
I'll just point out that engine manufacturers do not make oil filters.
All factory branded parts do is cost more.

But agree, filter and new oil is the place to start
As long as it meets spec.
Your post implies that all oil filters are created equal. This is not the case.
There are a lot of poor quality off-brand oil filters for sale that the unwary might use.
The oil filter is no place to save money and the cost difference isn't
great. It's a good idea to buy them where you buy your engine's
other routine replacement parts. They may not be that engine's
labeled part but it will be a known quality replacement filter.
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Old 08-18-2022, 05:43 PM   #12
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Quote:
Originally Posted by KnotYet View Post
Your post implies that all oil filters are created equal. This is not the case.
Well, I did say if it meets spec


Quote:
The oil filter is no place to save money and the cost difference isn't
great.
The cost difference is often 100% or more extra
If that's neither here nor there for you that's great

But not once in my 40 years of driving and boating have I heard of an engine fail caused by clean oil and clean filters that meet spec, regardless of branding or price.
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Old 08-18-2022, 05:57 PM   #13
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Quote:
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Well, I did say if it meets spec

The cost difference is often 100% or more extra
If that's neither here nor there for you that's great
While an oil container will have all the specs the oil meets clearly marked,
that is not common on an oil filter label - generally just a manufacturer's part number.
So 'meeting spec' is not at all a given.

When I'm changing 2-4 gallons of oil (or more) the addition cost of a known
quality oil filter amounts to a pint or two of known quality ale.

Worth it.

"But not once in my 40 years of driving and boating have I heard of an engine fail caused by clean oil and clean filters that meet spec, regardless of branding or price."

N=1
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Old 08-18-2022, 06:13 PM   #14
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Who did the oil change? I'm extremely cynical after some bad experiences with "mechanics". An example would be cross-threading a oil pan drain plug and having all the oil drain out. I would make sure the oil filter is screwed on tight and have fresh absorbent pads placed under the engine to detect any leaks. All the above comments are relating to the recent oil change. Just a matter of figuring out what changed.
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Old 08-18-2022, 06:47 PM   #15
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Quote:
Originally Posted by KnotYet View Post
While an oil container will have all the specs the oil meets clearly marked,
that is not common on an oil filter label - generally just a manufacturer's part number.
So 'meeting spec' is not at all a given.
But 30 seconds on the internet can fill in those gaps if there
Quote:
When I'm changing 2-4 gallons of oil (or more) the addition cost of a known
quality oil filter amounts to a pint or two of known quality ale.
Sure, but multiply that out over every purchase in your life and use that saving to buy income and it can be the difference between retiring at 40 or retiring at 70.
I chose to retire at 40.

It's also worth noting that a lot of paid mechanics will be using aftermarket filters as well.
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Old 08-18-2022, 06:48 PM   #16
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Quote:
Originally Posted by Simi 60 View Post
Well, I did say if it meets spec




The cost difference is often 100% or more extra
If that's neither here nor there for you that's great

But not once in my 40 years of driving and boating have I heard of an engine fail caused by clean oil and clean filters that meet spec, regardless of branding or price.

I tend to agree, but in this case where there is an issue, I think using the branded filter will help eliminate one possible cause. This is particularly front and center for me since my brand new engine exhibited oil pressure issues right from the start. It was never low enough to risk damage, but was consistently below specs. It turned out to be a faulty bypass valve, and pressures have been spot on ever since.
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Old 08-18-2022, 10:01 PM   #17
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Quote:
Originally Posted by Simi 60 View Post
But 30 seconds on the internet can fill in those gaps if there


Sure, but multiply that out over every purchase in your life and use that saving to buy income and it can be the difference between retiring at 40 or retiring at 70.
I chose to retire at 40.

It's also worth noting that a lot of paid mechanics will be using aftermarket filters as well.
There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.

John Ruskin

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Old 08-18-2022, 10:11 PM   #18
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Originally Posted by KnotYet View Post
There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey.

John Ruskin

As long as it meets the engine manufacturers spec

When it doesn't and you still use it that's when you need to worry.


There is a line where blind loyalty?/gullibility?/stupidity? meets price gouging.
A nice example is this

https://www.trawlerforum.com/forums/...27&postcount=3
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Old 08-18-2022, 10:24 PM   #19
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Quote:
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As long as it meets the engine manufacturers spec

When it doesn't and you still use it that's when you need to worry.

There is a line where blind loyalty?/gullibility?/stupidity? meets price gouging.
A nice example is this

https://www.trawlerforum.com/forums/...27&postcount=3
https://www.parts4engines.com/perkins-4-236-oil-filter/ or:
https://shop.perkins.com/parts/engin...2-70cfdb92b9d5

Sorry, I had to answer your post with the actual oil filter I would routinely
buy for my old but sweet-running Perkins engine.
It gave me great pleasure to spoil it with only the finest in luxury factory parts regardless
of cost...

I suppose you could buy an off-brand filter for a few dollars less but
these actual prices that I've actually paid are the reason I wonder why
you would repeatedly post about how expensive factory filters are.
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Old 08-18-2022, 11:08 PM   #20
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Quote:
Originally Posted by KnotYet View Post
https://www.parts4engines.com/perkins-4-236-oil-filter/ or:
https://shop.perkins.com/parts/engin...2-70cfdb92b9d5

Sorry, I had to answer your post with the actual oil filter I would routinely
buy for my old but sweet-running Perkins engine.
It gave me great pleasure to spoil it with only the finest in luxury factory parts regardless
of cost...

I suppose you could buy an off-brand filter for a few dollars less but
these actual prices that I've actually paid are the reason I wonder why
you would repeatedly post about how expensive factory filters are.
And that's fine for that example and in the US
But the suggestion was that the op buy a branded filter for a Northern Lights Genset
For that engine it's a NL-24-08001

Cheapest I have found online that will get one to oz is $35.58 plus $27.19 freight and USD
That's around $90 Australian.
https://www.ebay.com/p/2075300646

Northern lights agents over here don't even sell them
They sell these unbranded ones instead for $20
https://www.marineenergy.com.au/coll...et-spare-parts
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