Restarting a Yanmar 3YM20 after two years hibernation

sarabande

sarabande

Well-Known Member
Joined
6 May 2005
Messages
36,182
Visit site
That's it, I have had enough of this trappist land-based life. The boat will be readied for an early Spring launch.

The engine was last used in Nov2019, and apart from then draining the 'fresh' side, checking the anti-freeze, and removing the impeller, I have to confess that nothing has been done.

The boat is ashore and I have fresh water and 240AC. I'd like to turn the (very low hours) donk over by hand to circulate the oil a bit, but there's no decompressor lever. The manual suggests using the emergency stop button to allow the engine to crank but not start.

This seems to be a sensible procedure, but are there any other items or procedures which more experienced users would recommend please ?

I am readying a freshwater hose for insertion into the Vetus strainer (but not for use till the engine starts :) ) and the electrics, morse throttle, and other bits and batteries will be lubricated and tested.

Will the alternator need any work, e.g. checking the terminals for corrosion, etc.

What have I forgotten, please ?
 
Sounds like you have a sensible plan. I would ensure you have everything turned off whilst turning over by hand as sometimes they can start surprisingly easily! I would fill the intake from the strainer in advance as the impeller may not last long without water to lubricate it then get the hose in ASAP. Bon chance..
 
It would be very surprising if it started straight off after such a long layup. When I missed a season I did nothing on the following April, just turned it over until it fired, about 5 - 10 seconds. Oil pressure was established on the first turn, buzzer off almost instantly. You could slacken off the injector pipe nuts a little to make sure.

Turning it over by hand will achieve almost nothing. A gear pump needs revs to shift the oil and generate pressure. Bores are lubricated by splash once pressure is achieved
 
I like to add a bit of oil, letting that trickle down through the engine. No idea if it actually does any good! Also I give the flywheel a bit of a wiggle by hand to check that nothing is stiff.
The biggest problem tends to be fuel. It's prudent to sample the tank in case any bug has appeared. Also not a bad idea to check that there is fuel at the bleed point, could save a lot of cranking.

Once running, get the engine nice and hot to drive off any condensation, but keep an eye on it for anything wrong, e.g. slipping belt.
 
I would suggest putting fresh oil in, leaving the impeller out, make sure the cooling water is off, turn the engine over with the stop lever out until the oil pressure is good, then fire it up until it starts, shut it down, then put the impeller back in and take it from there. Good luck.
 
Last edited:
vyv_cox said:
It would be very surprising if it started straight off after such a long layup. When I missed a season I did nothing on the following April, just turned it over until it fired, about 5 - 10 seconds. Oil pressure was established on the first turn, buzzer off almost instantly. You could slacken off the injector pipe nuts a little to make sure.

Turning it over by hand will achieve almost nothing. A gear pump needs revs to shift the oil and generate pressure. Bores are lubricated by splash once pressure is achieved
Click to expand...
I ran my Yanmar 4JH4AE in October 2019 and didn't return to Greece until late September 2021. Unused for almost 2 years but it started immediately. I did try to count the seconds before it started but was surprised when it fired around the 2 second mark. Oil pressure also went up almost immediately.

It's done 2,070 hours since purchase in 2009. I did my usual layup stuff in 2019, oil change, anti-freeze flush, spray fogging oil, remove impeller & alt. belt, spray electrics, check elbow, misc. other small tasks.

I just connected turned the engine manually to check it was free, sprayed a little fogging oil into the intake, replaced belt and impeller (+ silicone grease). I had also checked the fuel tank. It only had 20-30 litres left in the tank, no sign of any bug and just a small amount of degradation products. I added a repeat dose of Marine16.

Storage procedure was reversed and I'm hopeful it will now be OK until 2022 season. I was obviously pretty lucky to start so quickly after 2 years.
 
vyv_cox said:
It would be very surprising if it started straight off after such a long layup. When I missed a season I did nothing on the following April, just turned it over until it fired, about 5 - 10 seconds. Oil pressure was established on the first turn, buzzer off almost instantly. You could slacken off the injector pipe nuts a little to make sure.

Turning it over by hand will achieve almost nothing. A gear pump needs revs to shift the oil and generate pressure. Bores are lubricated by splash once pressure is achieved
Click to expand...

That has advanced my understanding of how oil is circulated a lot. Many thanks
 
I'd worry more about the fuel in the tank than the engine. Then check the impeller has not stuck against the sides of the pump housing.

If it was mine - and I have a 3YM - I'd then just turn the key or press the start button depending on which control panel it has. Obviously give it water once it starts, which on a 3YM should be within a second normally. In the present surprisingly warm winter temperatures here in Cornwall I wouldn't normally even bother with the preheat, though after a year+ layup or if it was really cold I might coddle it with ten seconds of preheat.

I have more than once started diesels after 10 years or so of inactivity. Usually they started and worked fine, though that was in the days before they polluted diesel fuel with bio-muck.
 
It's an agricultural diesel engine, not some tetchy Bugatti!
Two years standing is nothing. There will be nothing wrong with any fuel in the system. The oil will be fine too for the short-term.
By all means ensure the impellor is free in its housing but otherwise just connect it up and start it. I wouldn't even change the oil until I'd got it good and warm first, and even then not as an urgency unless it showed serious signs of emulsification or condensation. Very likely the fuel will still be in the injectors and with a good handful of throttle as Yannies like it'll go pretty easily.

If it doesn't go the one thing I would strongly advise is adherence to the starter-engagement limitation times. Silly to burn that out! If you run up aganst those then bleed the fuel system before having another try. Further starting problems if happy injectors are bled = service the injectors. Find a local agricultural engineer/ diesel doctor/injection shop for that, not a marine $$$ one!

Turning it over by hand will do nothing whatsoever to the one oil-related thing that could hinder a start; poor compression due to a dry bore. OTOH turning it over briskly on the starter motor will splash-lube the bores nicely over a period of a few seconds and rejuvenate the seal.
Many, if not most engines will allow oil in the galleries to seep back to the sump overnight (your car quite possibly does - previous generations of cars all did). The few revs before the pump delivers pressure isn't on dry bearings anyway, the oil film remains (likely for decades). Don't sweat this one! (Light aircraft engines - Lycomings and Continentals - often allow 10-15 seconds running before the oil pressure light goes out, Oil pressure is only really needed for running inder load).
Far, far too much angst is unnecessarily expended on starting engines that have had a brief holiday.
It's a tractor engine. It won't come to any harm at all.

My treatment - check oil level, change impellor at this point if you wish but if it pumps water I'd leave that to do along with the other jobs later. (If a ten year resuss, I'd certainly change the impellor now) Get it running, warm it up properly. Leave overnight. Next day check rockerbox for excess condensation, that'll give advice for the future whether it tends to dampness inside. You'll now be greatly reassured at the way it fires up as a good Yannie will , and get it up to operating temp. Drop oil, change ALL filters and impellors at this point.

If it has a thermostat-insert change that too. They fail open (and often) so a weak thermostat = cold running engine and diesels don't like that.

Job jobbed.
 
Last edited:
sarabande said:
That has advanced my understanding of how oil is circulated a lot. Many thanks
Click to expand...
Not really, it's complete tosh.
A gear pump shifts a measured volume every rev, less what leaks through the clearances.
If the leakage is a lot at low pressure, you need a new one!

It might take quite a few turns to fill the oilways, if it has drained back.

But I'd only turn it by hand to check it hadn't seized or hydraulic locked. Should be fine, but maybe nice to be sure?
Once you're sure it rotates OK, as others have said spin it on the starter with the fuel shut off. At least that'll give the battery a good test.
I'd check the impeller visually and lube it with something convenient?
 
Wing Mark said:
Not really, it's complete tosh.
A gear pump shifts a measured volume every rev, less what leaks through the clearances.
If the leakage is a lot at low pressure, you need a new one!

It might take quite a few turns to fill the oilways, if it has drained back.

But I'd only turn it by hand to check it hadn't seized or hydraulic locked. Should be fine, but maybe nice to be sure?
Once you're sure it rotates OK, as others have said spin it on the starter with the fuel shut off. At least that'll give the battery a good test.
I'd check the impeller visually and lube it with something convenient?
Click to expand...
So where is the tosh bit? After saying that you agree with everything I say. There is no way a gear pump will deliver anything while an engine is barred over, the leakage through the teeth is too great.
 
The leakage through the teeth is not large with cold oil, particularly when the pump is not working against much pressure. The pump won't be working against any pressure until the oilways are filled. A gear pump does not need RPM to work.
 
Wing Mark said:
The leakage through the teeth is not large with cold oil, particularly when the pump is not working against much pressure. The pump won't be working against any pressure until the oilways are filled. A gear pump does not need RPM to work.
Click to expand...
I'm afraid you are demonstrating your ignorance of gears. There is always backlash, impossible to avoid. When the engine turns over at speed the driver tooth pushes against the driven tooth, taking up the backlash with a very small clearance. When the engine is barred over the clearance cannot be closed and the oil passes between the teeth.
 
vyv_cox said:
I'm afraid you are demonstrating your ignorance of gears. There is always backlash, impossible to avoid. When the engine turns over at speed the driver tooth pushes against the driven tooth, taking up the backlash with a very small clearance. When the engine is barred over the clearance cannot be closed and the oil passes between the teeth.
Click to expand...
Sorry mate, I've owned several BSA bikes with gear type oil pumps and I'm quite familiar with how long it takes oil to flow back through them and all that.
(Actually BSAs have a problem of the oil flowing the other way, it takes hours even if the pump is quite worn).
Also I've personally fitted an oil pressure gauge to an engine and watched the pressure go up turning the motor by hand.

Are Yanmar oil pumps even gear types?
This one appears to be a trochoid.
Yanmar Oil Pump | Oil Pump For Yanmar Engine
Not many big clearances in there.
 
Wing Mark said:
Sorry mate, I've owned several BSA bikes with gear type oil pumps and I'm quite familiar with how long it takes oil to flow back through them and all that.
(Actually BSAs have a problem of the oil flowing the other way, it takes hours even if the pump is quite worn).
Also I've personally fitted an oil pressure gauge to an engine and watched the pressure go up turning the motor by hand.

Are Yanmar oil pumps even gear types?
This one appears to be a trochoid.
Yanmar Oil Pump | Oil Pump For Yanmar Engine
Not many big clearances in there.
Click to expand...
I think that my Yanmar has a similar pump and I've seen it mentioned in other Yanmar manuals. i.e. A type of internal gear pump, not an external gear pump. I know that the leakage flow can be calculated for trochoidal pumps but to be honest, I just turned the engine manually to make certain nothing was seized before engaging the starter motor. :D:D I wasn't expecting it to actually pump any oil with the amount of movement to the crankshaft. I assume there will still be leakage between the gears, plus sides, housing and cover.
 
Last edited:
Tradewinds said:
Why be so rude? It's not necessary - really.
If you have a counter opinion that's fine - it's what makes the forum tick,
No wonder why so many can't be bothered to post nowadays.
Click to expand...
Well said and it is a continuing theme of long time and very experienced members leaving because it ceases to be worth the agro - it is not that they cannot take a bit of criticism it is just that they don't need to do it especially when expressed in a less than friendly manner.
There isn't a formal hierarchy of members but there are ones whose knowledge in particular areas is clearly superior and can be relied upon without more - we will each have our own views about who they are - ones who we hope will contribute to a thread because the thread would be very much better with their contribution. Vyv is very much in that camp and I frankly cannot see how his views on anything mechanical can be so casually dismissed as 'tosh'.
 
Poecheng said:
Well said and it is a continuing theme of long time and very experienced members leaving because it ceases to be worth the agro - it is not that they cannot take a bit of criticism it is just that they don't need to do it especially when expressed in a less than friendly manner.
There isn't a formal hierarchy of members but there are ones whose knowledge in particular areas is clearly superior and can be relied upon without more - we will each have our own views about who they are - ones who we hope will contribute to a thread because the thread would be very much better with their contribution. Vyv is very much in that camp and I frankly cannot see how his views on anything mechanical can be so casually dismissed as 'tosh'.
Click to expand...
Because he's wrong.
And arrogant with it.

I've not been on this forum long, but there is apparently a bit of a culture of a 'forum group think' on a few subjects which is quite at odds with knowledgeable people in the wider world. You can take the word of the forum's pet 'expert' as gospel if you like, but I'm hardly the only person who's turned an engine by hand and seen the oil pump to work.

I think people should question a lot of the stuff they read on here.
 
Oh dear oh dear

“I think here is another way of looking at it , possibly” is going to be a tad more pursuasive than
“ he’s x y z . oh yeah and it’s crap”
That’s just how society works

By the way I value what you have to say as much as I have valued and used other posters knowledge shared from their professional experience
 
You must log in or register to reply here.

Share this page

Top