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Old 28-11-2020, 19:30   #31
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Re: Yanmar SB12 won't fire - injectors work?

You dont want a parts manual you want a service manual to do valve adjustment & I can send you a copy but you need to send me a PM with your email. I dont want to put my email on a public forum. You can put your email address on here if you wish & i'll send it to you.
Basically you set the piston at TDC on the compression stroke & adjust the rocker arm gap gap to 0.2mm

Ok if you've had the exhaust manifold off recently & it wasnt blocked it should be ok
The injector can squirt but you have an intermittent problem so it may squirt when you are testing it & then the fuel supply gets interrupted for some reason when its running. You could have a hose getn blocked or fuel pickup or air leak or lift pump diaphragm problem which is why I suggested a temporary gravity feed
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Old 28-11-2020, 19:38   #32
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Re: Yanmar SB12 won't fire - injectors work?

Quote:
Originally Posted by rockin411 View Post
I took the bonnet off the other day but didn't know what I was looking at. I didn't see anything in the manual about adjusting the tappet settings so I really have no idea where to start. I looked at the provided page in the parts manual to try to understand but I'm lost as to how the valves work.
...........
Youtube will be your friend.

Essentially you are measuring the maximum gap between item #1(#2) and item 39(40). Item 39(40) sits on top of item 27(28).

You measure the gap by inserting a the correct sized 'feeler gauge' into the gap. It should be 8 thousands of a inch (0.2mm).

You adjust the gap by loosening the lock nut (53) and turning screw 37. When correct, lock the nut again.

Engine should be cold.

The piston should be at TDC on the compression stroke.

EDIT: Crossed posted with Compass790
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Old 28-11-2020, 19:45   #33
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Re: Yanmar SB12 won't fire - injectors work?

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Originally Posted by Wotname View Post
Youtube will be your friend.

Essentially you are measuring the maximum gap between item #1(#2) and item 39(40). Item 39(40) sits on top of item 27(28).

You measure the gap by inserting a the correct sized 'feeler gauge' into the gap. It should be 8 thousands of a inch (0.2mm).

You adjust the gap by loosening the lock nut (53) and turning screw 37. When correct, lock the nut again.

Engine should be cold.

The piston should be at TDC on the compression stroke.

EDIT: Crossed posted with Compass790

I think your explanation much better suited to O.P. cobber
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Old 28-11-2020, 20:07   #34
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Re: Yanmar SB12 won't fire - injectors work?

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Originally Posted by Compass790 View Post
I think your explanation much better suited to O.P. cobber
Yeah but... you beat me by 8 minutes
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Old 28-11-2020, 21:13   #35
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Re: Yanmar SB12 won't fire - injectors work?

One more dumb question: Where do I locate this TDC mark?

P.S. That YSM manual you sent me is SO much better than the YSE.

Thanks again!
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Old 28-11-2020, 21:31   #36
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Re: Yanmar SB12 won't fire - injectors work?

You have to remove starter motor or starter motor cover if its a hand crank engine to find the flywheel mark.
I doubt very much that setting the valve clearances will fix the problem but it should be done & you can see if the valves are going up & down properly if you turn it over decompressed with the rocker cover off. Better to use handcrank for that than starter so not to spray oil.



I think you should try a gravity feed next, you can use an outboard tank with fuel line direct to injection pump. Still most likely a fuel issue IMO.


Edit: you can do it without the timing mark if you get it to the point where both valves are closed on the compression stroke if you turn it over slowly & think about how the valve sequence works. The rocker arms should be rocking at TDC. Not sure you should try that as you are a newbie, safer to do it the way the manual says
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Old 29-11-2020, 12:40   #37
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Re: Yanmar SB12 won't fire - injectors work?

Day 4: Sprayed starter fluid and it started right up at high RPMs - thought I had a run away engine but it shut down after about 15 seconds when I turned the fuel off. I tried again at idle and it started right up. Tried again an hour later and started normally at idle.

At this point I don't even know what to do - I was prepared to look at the tappet clearance but didn't even bother since it runs fine. I'm wondering if it's something like a intermittent stuck valve that frees itself over night??
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Old 29-11-2020, 15:21   #38
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Re: Yanmar SB12 won't fire - injectors work?

Well you probably still need to find the problem as it will probably re-occur at the most awkward moment.
You could be lucky but I wouldnt bet on it.


Be a good idea to read the manual for the service intervals & the troubleshooting. YSM one probably better for that.

Still think its most likely to be a fuel delivery issue. Have you ever cleaned the tank or checked the pickup tube?
Another ? you need to ask is why did you have a poor injector spray pattern in your first vid?
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Old 29-11-2020, 18:14   #39
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Re: Yanmar SB12 won't fire - injectors work?

Thanks for your help. I'm running the fuel straight from a gerry can with fresh fuel to eliminate that as a possibility. I think the uneven spray in that first video was the air coming out of the shaft blowing the injector(it was right on top of it) - I was sure to move the injector out of the way in the second video.

I was thinking of rebuilding it but there are a number of issues that hold me back. Mainly I'd have to pull it from the boat because the mounts are rotten and need to be fixed first and second i don't know what I'm doing. If i go to that trouble, I'm thinking electric. I just want to sail though - I'm on a lake and just need to get in and out of my slip.

Thanks again!
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Old 29-11-2020, 20:02   #40
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Re: Yanmar SB12 won't fire - injectors work?

Please report back what you find after gravity feeding ( I hope filtered fuel ) straight to the injection pump.
Yes if you are only lake sailing I can see your point re electric propulsion. An outboard is another alternative.
It's understandable not wanting to do the rebuild if you lack the know how.
I'd be interested in looking at your takeout engine if I wasnt 5000 miles away. Looks a good rebuild candidate to me due to being a freshwater boat.
Mind you it didnt sound like it needed a rebuild, just the problem sorted.


Good luck
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Old 04-12-2020, 09:00   #41
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Re: Yanmar SB12 won't fire - injectors work?

I had a one cylinder Ferryman diesel which also started quickly and ran well (generator). If it was sitting for a couple months and the exhaust valve was open, apparently a small amount of rust accumulated on the valve or valve seat due to condensation from water further down the exhaust system leading to (undetectably) low compression. Removing a couple screws on the exhaust “manifold” gave me direct access to the exhaust valve. Rotating the engine to ensure the valve was closed then pouring a teaspoon of oil onto the valve allowed for enough compression to start readily. Running pretty much instantly re-polished the surfaces and all was well again.
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Old 04-12-2020, 19:48   #42
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Re: Yanmar SB12 won't fire - injectors work?

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I had a one cylinder Ferryman diesel which also started quickly and ran well (generator). If it was sitting for a couple months and the exhaust valve was open, apparently a small amount of rust accumulated on the valve or valve seat due to condensation from water further down the exhaust system leading to (undetectably) low compression. Removing a couple screws on the exhaust “manifold” gave me direct access to the exhaust valve. Rotating the engine to ensure the valve was closed then pouring a teaspoon of oil onto the valve allowed for enough compression to start readily. Running pretty much instantly re-polished the surfaces and all was well again.

I did advise OP to take rocker cover off & check that valves were operating freely.
If you leave a single at TDC on compression stroke that ensures that the seat/stem wont rust & the combustion chamber is sealed off from the salt air ( kind of anyway)
Yanmar gives that advice in their manual for '70's era singles.
Thought it was a good tip & try & remember to do that when shutting down.
O.P. has gone quiet, maybe he's installing electric drive??
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Old 04-12-2020, 23:47   #43
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Re: Yanmar SB12 won't fire - injectors work?

THIS...
Quote:
Originally Posted by Compass790 View Post
.......
If you leave a single at TDC on compression stroke that ensures that the seat/stem wont rust & the combustion chamber is sealed off from the salt air ( kind of anyway)
Yanmar gives that advice in their manual for '70's era singles.
...............
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Old 05-12-2020, 00:20   #44
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Re: Yanmar SB12 won't fire - injectors work?

I happened on the WD 40 as starting fluid for diesels in a Don Casey book.
I think it's because WD 40 is mostly diesel. I don't like WD40 as a penetrating oil, but I used it to start an old (in good condition, FWC, good compression) 2cyl Volvo, that had sat for 8 years. Got it to run for a few beats, gave me the courage to get clean fuel to it, and it started on the regular fuel.


Regular starting fluid can fire when the piston is on the way up, and cause damage (I've used , carefully, though) WD is less volatile, and less likely to cause damage. (Says D Casey)
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