Help with Low Oil Pressure troubleshoot

Ralph Johnstone · Jul 30, 2023

Afraal said:
The engine lost a bit of power, so I shot it down inmeaditely.

I was going to say an accidental ground on the alarm wiring was the cause of the alarm until you said the engine lost some power. Are you sure of this or could it just be your impression after being shocked with the unaccustomed low oil pressure alarm. Obviously you only have an oil alarm and not a pressure gauge.

Afraal said:
It notice it was ok at idle before I shot it off

This tells you the sensor is probably working as it can sense a return to normal higher pressure.

The only "common" causes of actual low oil pressure are either :
- a dirty oil filter
- extremely dirty oil
- a low oil level
- extremely low viscosity oil

However, I know you've checked all of those before asking your question (all except the low viscosity).

When you checked your crankcase oil level, any chance it was abnormally high ? If so, this "may" be diesel fuel leaking into your crankcase oil which would cause a low viscosity.

BTW what are the operating hours on the engine and the age of the engine ?

Ralph Johnstone · Jul 31, 2023

Afraal said:
The engine is a 2000 model and it has 135 hours, give or take a few hours.

Just a curiosity here, but that is an awfully low number of operating hours for a 23 year old engine. My 1998 has about 2200 hours on the engine. But your low hours has nothing to do with your problem.

I know this is no help, but if you did have a pressure gauge on your oil, it would simplify things. Diesels are so indestructible, a lack of oil pressure is a rarity, and alarms usually boil down to an electrical fault.

@Stu Jackson , any thoughts on what's going on here ?

Ralph Johnstone · Jul 31, 2023

Afraal said:
I did some research last night and found out the the Universal 25XPB has an Oil Pressure Shutdown switch that basically kills the engine if there is low oil pressure.

I've heard this before and I assume the kill switch is connected to an audible alarm. It wouldn't make sense not to. My engine is a Yanmar so no first hand knowledge of the Universal XP25.

Afraal said:
the "low oil pressure" alarm rang and the red light in the instrument panel turned on. The engine lost a bit of power, so I shot it down inmeaditely.

This may speak to the momentary engine shut down by the low pressure cut out circuit which you experienced.

Afraal said:
The CatalinaDirect site says it is one of the items to keep in you spare tools box, because it can fail.

This may be your first step in remedying the problem. I don't think the cost of the item is prohibitive and you should be able to replace it yourself. Ask CD for any literature they have on the device and how to replace it.

I'm sailing out of here this afternoon and will be back on Friday. Too cheap for a data plan on my phone so cannot check back. Looking forward to hearing good news on Friday.

Stu Jackson · Jul 31, 2023

Afraal said:
the "low oil pressure" alarm rang and the red light in the instrument panel turned on. The engine lost a bit of power,

Do you have a separate low oil pressure alarm?

capta · Jul 31, 2023

I'd check the compression first thing. Low oil pressure, loss of power, and fuel in the oil are a combination that is indicative of a problem with rings.

RoyS · Aug 1, 2023

I recently installed an oil pressure gauge in place of the original low pressure switch on my Yanmar. I use straight 30 Wt. oil. When the engine first starts the oil pressure is about 85 psi at 1,000 rpm. When the engine is hot the oil pressure is about 10 psi at 1,000 rpm and the alarm sounds. Raising the idle speed to 1,100 rpm silences the alarm. These oil pressure senders and switches can vary slightly and send a low pressure alarm when no real fault exists.
EDIT: The original Yanmar low oil alarm switch is set to close at about 3 psi. My new VDO sender has the alarm switch set to about 6 psi and sounds at 1,000 rpm when the engine is hot.

jviss · Aug 1, 2023

RoyS said:
When the engine is hot the oil pressure is about 10 psi at 1,000 rpm and the alarm sounds.

Does that not concern you? I would be very concerned about anything lower than about 25 psi.

RoyS · Aug 1, 2023

See my edit above. So, no.

jviss · Aug 1, 2023

RoyS said:
See my edit above. So, no.

O.K., but still - if you google diesel engine oil pressure you're see that most folks call anything below 20 psi low oil pressure:

"What is considered low oil pressure in a diesel engine?
If your pressure is lower than 20 PSI or falls below the normal range of the gauge, it needs immediate attention, and it usuallz a consequence of another problem. However, it is difficult to determine the cause of low oil pressure. So the best option is to turn the engine off."

Low Oil Pressure

How many hours on your engine?

RoyS · Aug 1, 2023

What "most folks" on google claim is less important to me than the fact that Yanmar's engineers set the low oil pressure alarm at 3 psi. I rebuilt my engine, including all bearings, thirteen years and about 1,000 hours ago. It is only this season that I have an oil pressure gauge, so I have no real personal experience with diesel oil pressure. Maybe someone else with personal diesel engine oil pressure experience can comment.

RoyS · Aug 1, 2023

OK, jviss, you got me to investigate oil pressure on my Yanmar 2qm15. According to the Yanmar Service Manual, oil pressure "idling" should be 7 psi. and 35 to 50 psi at 3,000 rpm. (Page 6-7 Yanmar 2qm15 Service Manual) Keep in mind that my readings in the above postings are not from a calibrated test gauge but from a common electrical sender and dash gauge. I do not think the 20 psi value from google applies to my engine and I have no idea what the original poster's engine should be showing.

jviss · Aug 1, 2023

RoyS said:
OK, jviss, you got me to investigate oil pressure on my Yanmar 2qm15. According to the Yanmar Service Manual, oil pressure "idling" should be 7 psi. and 35 to 50 psi at 3,000 rpm. (Page 6-7 Yanmar 2qm15 Service Manual) Keep in mind that my readings in the above postings are not from a calibrated test gauge but from a common electrical sender and dash gauge. I do not think the 20 psi value from google applies to my engine and I have no idea what the original poster's engine should be showing.

I'm on my way to my boat soon and I'll look at mine carefully. I have a gauge as well as the low pressure alarm switch.

It must be that the 20 psi figure doesn't apply to your engine if Yanmar says 7 psi at idle. It's just that it intuitively feels low to me, but what do I know? My knowledge of "normal" oil pressure is anecdotal, i.e., engines I've owned, and what I've read.

Stu Jackson · Aug 1, 2023

Afraal said:
HI Stu... not sure what you mean by a separate alarm

As I quoted in my first post, you originally said:

Afraal said:
the "low oil pressure" alarm rang and the red light in the instrument panel turned on.

You also said you have an XP25 engine. If it is, then it is an M25XP. However, most C310s I am aware from this very forum which uses it as its association website, hve M25XPB engines, which despite the teeny difference are two different engines.

Far as I know, neither one of 'em have SEPARATE oil alarms in their cockpit panels. The single alarm and light are for both oil and temperature.

Does your engine have a separate oil alarm (buzzer & light) and a separate temperature alarm or do both alarms use the same light and buzzer? How did you know it was low oil? Could it have been hi temp?

kloudie1 · Aug 1, 2023

One item not discussed is the oil pressure control bypass, I don't know where it is on the Kubota engine, but it is a little spring loaded ball valve in the oil pump discharge path, usually just after or integral to the oil filter bracket. . If a small piece of debris gets stuck in the valve, that can cause a sudden pressure drop.. In the QM diesels, the valve is in the oil filter spin-on male boss.. In the "Lubrication System" section of the engine manual (In the downloads section of this site) the location and parts are shown. It can be cleaned/checked after removing the oil filter.
.

jviss · Aug 2, 2023

RoyS said:
OK, jviss, you got me to investigate oil pressure on my Yanmar 2qm15. According to the Yanmar Service Manual, oil pressure "idling" should be 7 psi. and 35 to 50 psi at 3,000 rpm. (Page 6-7 Yanmar 2qm15 Service Manual) Keep in mind that my readings in the above postings are not from a calibrated test gauge but from a common electrical sender and dash gauge. I do not think the 20 psi value from google applies to my engine and I have no idea what the original poster's engine should be showing.

Following up on this. Ran the engine today. It's a Westerbeke 38B-FOUR, based on a four cylinder Mitsubishi engine.

Cold I get 75 or 80 psi at idle.
Hot I get 50 psi at idle.

RoyS · Aug 3, 2023

Interesting. What was the tach reading?