Yanmar SB8 no lube oil

[Bbrad10]

First off, I’m new on here, but I’ve been following so many of these threads through google over the last couple months and y’all’s advice (shoutout Wotname in particular) has been invaluable, so thank you. I never would have made any progress on a weird diesel engine with no glow plug that’s 20yrs older than me without this community.

So anyways, I have a Yanmar SB8 from a 1978 Hunter and oh boy when I got her she needed work. I’ve taken everything apart, cleaned and adjusted the valves, changed the oil, replaced a bunch of gaskets, yada yada. It will now start and run only when the regulator is at full throttle, so I have further adjusting to do, but whatever it starts and runs until I idle down and can be a later thread if I don’t figure it out.

But as the title to this one says, I am not getting any lube oil pressure. The engine has plenty of oil, the lines (even the cast ones) have all been blown through with air to make sure they’re clear, the filter has been cleaned out of all the crud. Before starting I’ve made sure to cover the valve/rocker arms/rods with some fresh oil and I was hoping the engine would just generate it’s own pressure since it seems it’s a gear driven pump, but no joy. So I idle down within a minute, before it can get too hot.

I took out the pressure sensor and tried to crank it to see if any oil was even making it through the filter, also no luck. When I reference the parts manual it looks like I still have everything in place. So, I’m a bit stumped, if anyone has any idea what I should do please let me know, thanks for your time!

[srv express]

All I have are more checks for you to perform
Note: The engine takes far too long to fill the Oil Filter, once the Oil filter and Oil Cooler are full then the engine builds Oil Pressure.
#1 Pull the Oil Filter off, see if there is Oil in it also see if Oil comes out when ya turn the engine over without the filter installed. Check for Oil at the oil cooler too (Fill with oil the correct Oil filter and reinstall all). Possible the incorrect oil filter was installed?
#2 Back feed the oiling system (With oil) to prime the pump also at this point ya need to do this to avoid further engine damage because, the oiling system is now oil starved.
#3 If still no oil comes out, I would guess the Oil pump pick up tube fell off and is laying in the bottom of the oil pan.
#4 Take two pills and call me in the morning.

[skipperpete]

Originally Posted by Bbrad10

First off, I’m new on here, but I’ve been following so many of these threads through google over the last couple months and y’all’s advice (shoutout Wotname in particular) has been invaluable, so thank you. I never would have made any progress on a weird diesel engine with no glow plug that’s 20yrs older than me without this community.

So anyways, I have a Yanmar SB8 from a 1978 Hunter and oh boy when I got her she needed work. I’ve taken everything apart, cleaned and adjusted the valves, changed the oil, replaced a bunch of gaskets, yada yada. It will now start and run only when the regulator is at full throttle, so I have further adjusting to do, but whatever it starts and runs until I idle down and can be a later thread if I don’t figure it out.

But as the title to this one says, I am not getting any lube oil pressure. The engine has plenty of oil, the lines (even the cast ones) have all been blown through with air to make sure they’re clear, the filter has been cleaned out of all the crud. Before starting I’ve made sure to cover the valve/rocker arms/rods with some fresh oil and I was hoping the engine would just generate it’s own pressure since it seems it’s a gear driven pump, but no joy. So I idle down within a minute, before it can get too hot.

I took out the pressure sensor and tried to crank it to see if any oil was even making it through the filter, also no luck. When I reference the parts manual it looks like I still have everything in place. So, I’m a bit stumped, if anyone has any idea what I should do please let me know, thanks for your time!

G’day Bbrad, this happens from time to time, especially if the oil pump is a bit worn. I don’t take any chances with dry startups and always prime the system ( even fill it too) with oil under pressure , usually through the oil sender port on the block from a service tool I made up….. a scuba tank, an inline bypass oil filter, a collection of hydraulic hose and fittings, gauge and a shutoff tap. I use air to pressurise the oil in the tank and when the level on the dipstick reaches the full mark I shutoff the flow , start the engine and watch the pressure gauge. You could create a simpler version, the aim is to fill every gallery, nook and cranny …but mostly the oil pump casing.
You could also try grossly overfilling the crankcase and rotating the engine manually, when you see oil at the gauge sender hole, drain off the excess and try for a start. Don’t keep spinning the engine or running it with zero oil pressure or you might pick up a bearing……. Nope, you WILL pick up a bearing!

[Searles]

First check that the oil gear pump is turning as the drive gear is keyed to the drive shaft ,second end play is critical for these pumps ,the gasket is about 5 thou ,if the clearances aren’t close to specs they will not prime or hold a prime .⛵️⚓️

[Bbrad10]

Thank you for the replies already!

So the oil filter is one of those metal ones you just twist on startup a bit opposed to the typical can so it’s the original one; but it’s still in good condition primed and clean. When I took the oil pan off I made sure to re-thread the tube, and the line is clear of blockage because air bubbles show in the pan when blowing through the line. The gears are all turning together, when I had the timing cover off I inspected the whole pump and (as someone with no prior diesel experience) everything looks good! But piece for piece everything is where it is supposed to be, it looks like there is no real wear on it.

I’ll see what I can do to prime the system like Pete suggested by pressurizing the oil today, though I’ve never done anything like that before so I’ll have to head to Youtube or something. If that doesn’t work I’ll take the timing cover back off and check that spacing like Searles suggested. Thank you again for your time, safe winds everyone

I’ll report back, any other ideas are welcome too.

[Bbrad10]

Hey Pete do you by chance have a picture of your setup so I have something to reference?

[srv express]

Originally Posted by Bbrad10

Thank you for the replies already!

So the oil filter is one of those metal ones you just twist on startup a bit opposed to the typical can so it’s the original one; but it’s still in good condition primed and clean. .

Ok, I think we're getting closer to the bottom of the problem.

Recommend; Please, replace the Oil Filter with a WIX or good quality oil filter and fill the filter with oil prior to installing.

Also we can guess some more but, let us see what the engine can tell us;
drain the old filter upside down for a couple days and then cut the top off
(of the old oil filter) and inspect the filter element for metal shavings.
As you say or as I understand this is the original oil filter OMG hopefully not but, if it is, the whole story will be inside it or at least some of the story.
Hopefully this inspection will shine some light on what has happened to the engine AND !AND! AND if the filter is plugged just maybe the fix with a WIX!
Please, do tell all, I'm dying to read about what you find inside...

[Kello]

Too darn hot today to work on my own problems, so I’m visiting CF to enjoy other people’s problems. I’m too lazy to google what an SB8 is, but it is a Yanmar so that’s interesting. Post some pics for us!

When studying to learn how to rebuild my Yanmar, I learned one of the IMPERATIVE things to do for every rebuild is to renew the oil pump. On my Yanmar the oil pump is gear driven and is installed under the gear cover, not toooo difficult to access by itself.

Is your oil pressure sensor screwed into a damper? If so, the damper has a tiny hole for the oil and it clogs easily. Whether it is straight thru or on the side, it can be cleared with a straightened paper clip. Drop the damper in a cup of mineral spirits and let it soak for a bit, get a small tube brush and clear the passage/s, and push the paperclip thru the little orifice/s. Fill the damper with mineral spirits and be sure it runs freely out the other hole.

The sensors also get plugged with crud. Fill the passageway with mineral spirits, let it soak for a minute or two, maybe poke the paperclip around there a little bit, shake it out onto a paper towel and you will see the crud. Do it again. And again. And let it soak longer. And again. And by now you should be frustrated and will go buy a new pressure sensor, and let the old one soak until it is clean and keep it for a spare after you check that it still works.

When you “took everything apart” did you clean the block? Oil galleries DO get cruddy, and it is also possible that a piece of gasket from your disassembly is blocking one of the passages. My Yanmar, probably 20 years newer than yours, has plugs everywhere that can be removed to clean passages.

One of those plugs is immediately after the oil pump, see if your engine has one of those, and use that port to prime the oil system, first stop is the oil filter, so look for that on the block casting, don't use ports after the oil filter to prime the system. YouTube has several videos of guys who have made their own oil priming pumps for $20 using pressure sprayers from Home Depot, and the like. Or I hear you can buy a ready made one for about $300.

[srv express]

Originally Posted by Kello

Too darn hot today to work on my own problems, so I’m visiting CF to enjoy other people’s problems. I’m too lazy to google what an SB8 is, but it is a Yanmar so that’s interesting. Post some pics for us!

When studying to learn how to rebuild my Yanmar, I learned one of the IMPERATIVE things to do for every rebuild is to renew the oil pump. On my Yanmar the oil pump is gear driven and is installed under the gear cover, not toooo difficult to access by itself.

Is your oil pressure sensor screwed into a damper? If so, the damper has a tiny hole for the oil and it clogs easily. Whether it is straight thru or on the side, it can be cleared with a straightened paper clip. Drop the damper in a cup of mineral spirits and let it soak for a bit, get a small tube brush and clear the passage/s, and push the paperclip thru the little orifice/s. Fill the damper with mineral spirits and be sure it runs freely out the other hole.

The sensors also get plugged with crud. Fill the passageway with mineral spirits, let it soak for a minute or two, maybe poke the paperclip around there a little bit, shake it out onto a paper towel and you will see the crud. Do it again. And again. And let it soak longer. And again. And by now you should be frustrated and will go buy a new pressure sensor, and let the old one soak until it is clean and keep it for a spare after you check that it still works.

When you “took everything apart” did you clean the block? Oil galleries DO get cruddy, and it is also possible that a piece of gasket from your disassembly is blocking one of the passages. My Yanmar, probably 20 years newer than yours, has plugs everywhere that can be removed to clean passages.

One of those plugs is immediately after the oil pump, see if your engine has one of those, and use that port to prime the oil system, first stop is the oil filter, so look for that on the block casting, don't use ports after the oil filter to prime the system. YouTube has several videos of guys who have made their own oil priming pumps for $20 using pressure sprayers from Home Depot, and the like. Or I hear you can buy a ready made one for about $300.

Yes, excellent. Do this!

[skipperpete]

Originally Posted by Bbrad10

Hey Pete do you by chance have a picture of your setup so I have something to reference?

No pics of my actual one (it looks well used and very industrial) but here’s a couple of pics of the commercially available ones. No self respecting diesel mechanic would start a newly rebuilt engine dry, at the very least with no access to a prelube tank an engine should be cold cranked with the injectors out and the oil gallery open till oil spurts out. We almost always pre lube engines that have been laid up for over 6 months as part of the pre start procedure.

[Searles]

Just a bit more on the oil problem there is a spring loaded relief valve after the pump ,also you should be able to get good oil pressure by de compressing the engine and hand winding it over ,donot fire the engine until good oil pressure is evident.⛵️⚓️

[Bbrad10]

Hey all, thank you again for the replies. I’ve been busy doing so many projects, you know how it goes.

As for the oil system, I bought a cheap transfer pump from harbor freight, took the valve cover + rocker arms off and from the delivery nipple I pumped oil down into the engine. Worked like a charm to prime everything up. I checked for oil at sensor, was good, I checked for oil in the filter, was good. When I cranked the engine still no pressure it seems. I removed the pressure sensor and screwed in a pressure gauge to check, no luck.

Just want to say again that the filter is good. Even though it’s original, it isn’t the problem. When I opened it up there was a bit of crud (less than I’d expect in a 45yr old engine) so I cleaned it out real nice and now she looks just like the picture at the link below. Like I said, it isn’t a traditional filter. It’s this style:

https://discountmarinesource.com/sto...oduct_id=94001

Unfortunately the SB8 also doesn’t have any plugs to easily clean the inner oil chamber, but, luckily, when I took everything apart I blew through the lines with a can of compressed air, and then lightly with an air compressor, air was clearly coming through everything in the way it should, so I don’t think it’s a blockage. I will put the sensor in mineral spirits to clean it, however, it isn’t in a position to restrict flow so I believe it is simply a old pressure sensor rather than anything modern with valves that could get stuck.

My next step I guess is to check that clearance on the back of the pump. Perhaps some of the air moved something, though the pump re-installed afterwards. Maybe I re-installed incorrectly, I guess we’ll see. Will report back, thanks again for the help everyone ��

[skipperpete]

I’ve never worked on one of these Yanmar’s so I browsed the parts book to try to understand how your oil pump could fail to deliver. I suppose its possible for the oil pump drive key to be sheared (or missing) but if that’s the water pump">raw water pump drive tang slot on the end , you could very quickly confirm or dismiss this line of thought by turning the engine with the raw water cover plate removed.

[Wotname]

Let's go back to basics...

When did the engine last have oil pressure?
What event has happened since the engine last had oil pressure?

This event is first and most likely place to look. I'm going to take a GUESS and say the oil pump has been disassembled and has not been reassembled correctly. It is fairly hard to get it wrong but...sometimes it happens.

I have no direct experience with the SB oil pump but I am carnally familiar with the YSE / YSB oil pump. It is my understanding that the well known problems associated with the YSE / YSB oil pump were resolved with SB oil pump.

Nevertheless it would pay to check the side clearance between the outer rotor and the housing (items #5 & #8 on SkipperPete's attachment) along with the inner and outer rotor lobe clearance (items #8 & #2). These should be 2 or 3 thou and the smaller the better.

More importantly is the end plate clearance and AFAIK, this is determined by the thickness of the gasket (item #6). This critical and I THINK if this gasket is too thick, you might get the problem of low or no oil pressure. However I might be wrong having no direct experience of the SB oil pump pump. The end plate clearance of the YSE & YSB oil pumps ARE critical.

Also check the woodruff key (item #13) and drive pin (item #4) are in place.

The end plate (item #7) should only go one way (I THINK) but check it anyway and the pins (Item #12) are fitted correctly.

Is it possible the oil pressure relief valve has not been refitted correctly (items #1, #2 & #3 on my attachment)?

Hope you get it sorted!


BTW, I agree the oil filter will NOT be cause of your problem (unless the internal cover was not refitted), and I have to correct a minor error upthread. The T handle shim filter is the traditional style of oil filter and can be dated back over a 100 years being fitted to early aero engines. The cartridge and spin on filters that we see today is a modern concept!