Yanmar SB12 won't fire - injectors work?

[Wotname]

Originally Posted by CF32907

.......... You only need compression and fuel to make a diesel run. Pop the head, clean, clean valve seats and check valve for proper rise and fall. Put it back together and off you go. Iron main back in service. Hope this gives you some insight.....
Capt. Vince Rakstis, Ret. MS St.Petersburg, Fl.

Let's not forget it needs air as well to make a diesel run.

While it is unlikely the intake side would suddenly block, I have seen occasions where the exhaust side gets so clogged that the engine won't breathe. Works OK one month but not the next.

[Compass790]

I'll post a link from Teknsihn another Cf user showing his new injector nozzle spray pattern from a yanmar single.
If you watch it in freeze frame & compare it to yours you will see the big difference.
Check your valves are operating freely when you do the v/v clearances.

https://www.youtube.com/watch?v=HSBeCz0OIIE

Hope that helps.

[rockin411]

Thanks for all the great info. I'm heading out to the boat now to first try the starter fluid/hairdryer and check the exhaust and intake airflow.

I agree the injector spray is too wide and a little uneven but could that change suddenly? Shouldn't it at least sound like it wants to start if it's getting fuel and always started easily and run fine in the past? It seems more like it's compression.

I'll report back later today.

[rockin411]

Well I don't know what to report - I tried the starter fluid and heat gun in intake and it seemed to help but definitely not close to starting. I then removed the exhaust hose and was getting a little water and puff of smoke when i turned the key so I assume all is good there. I then tried to engage the decompression lever and release as I was starting and no luck there. I tried a few more squirts of starter fluid and still nothing. I gave up and moved on to other projects...

An hour later before calling it a day I tried one more squirt of starter fluid and it started right up (even with the bad injector spray pattern)! I had turned the water off so I immediately shut the engine down and turned the water back on. It restarted within 3 seconds of the key turn.

I will try again tomorrow with a cold start. Who knows?

Time to look at electric motors perhaps as I have little confidence in this thing.

https://www.youtube.com/watch?v=yJ3H...ature=youtu.be

[grantmc]

Originally Posted by CF32907

Hi All, CaptVR here
... You only need compression and fuel to make a diesel run. Pop the head, clean, clean valve seats and check valve for proper rise and fall. Put it back together and off you go. Iron main back in service. Hope this gives you some insight.....

Above is good advice. But one other thing, and this is classic for a YS engine and CaptVR likely assumes you'd know to always replace a head gasket when you 'pop the head' so didn't state it.

YSB is real old style, going back to the days of periodic decarbonising. Also it is a horizontal engine and it is raw water cooled. The water jacket includes the head so water is passing through the head gasket continually when running. Over time the water corrodes the head gasket resulting a loss of compression. And I assume it's worse with sea water but not sure.

Good preventative maintenance includes replacing the head gasket every 3 or 4 years And invariably you'll find the gasket corroded on the lower side.

It isn't so bad when motors are used very regularly (at least weekly). What can happen is that once the gasket is really stuffed it actually lets water in to the chamber and the water sits on the (obviously) the low side. Next time someone tries to start, the piston hits water and water doesn't compress. As implied, with regular use not such an issue as the water will be a minut quantity, vaporise and just be blown out with exhaust, but compression very slowly reduces as the gasket corrosion continues.

It's not a particularly difficult job to get the head off. When there isn't much room, many engine bays with YSBs have a little removable window beside the head. The kindness (mixed with much frustration perhaps) of owners long past.

Leave the fuel system alone; also that engine has a pre-combustion chamber so not a good idea squirting starter fluid down the air intake.

Change the Oil! If you can find some buy an oil designed for old diesel engines. Engine only holds a tad under a litre (I think that's 2 of your strange pints or is that a quart?). Another thing that can reduce compression. The YSBs don't have an oil filter so the oil really does go the blackest of blacks. But it eventually gets kind of gluggy and its viscosity increases. Also you can never get all the oil out so new oil is immediately contaminated.

Again regular use, and also running the engine long enough once it's hot results in some of the oil contaminants (and any suspended water droplets) to pass through to the exhaust. A common issue causing short periods between failure are the yachties that just start their motor and once they're out of the marina, up with the sails and off with the motor (and the reverse when they arrive back). The poor old motor doesn't even get to running temperature. It's a good thing in the long term to run the motor for a half hour or so before you turn it off.

Blocked exhaust can also be the cause. Old rubbersised exhaust does break down. That old engine will be at least 50 years old, amazing how well so many of them are still going. If only the parts weren't so expensive.

[Wotname]

^^ all good advice grantmc however a reminder for other readers, the OP has a SB12, not a YSB12.
The SB12 has a vertical cylinder and so suffers fewer head gasket problems and less chance of cooling water entering the cylinder.

[grantmc]

Originally Posted by Wotname

^^ all good advice grantmc however a reminder for other readers, the OP has a SB12, not a YSB12.
The SB12 has a vertical cylinder and so suffers fewer head gasket problems and less chance of cooling water entering the cylinder.

Eek I read, I guess, what I wanted to see and not what was presented.
Thanks Wotname for the correction.

[Compass790]

Rockin411. if I was you I'd just try & find the source of the problem.
It not the same as being there listening to the vid but the motor doesnt sound bad to me & I know what a bad one sounds like.
I'd still remove the exhaust pipe that bolts to the head & check the exhaust port isnt blocked if you havent done that for a long time but it sounds like a fuel problem. You've pretty much proved it isn't a compression issue if you started the 2nd time without starter fluid, if it isnt an intermittent fault like a valve jamming.

They are simple easy to repair engines that are long lasting & IMO a lot less hassle to reco one than put in electric propulsion Though electric propulsion would be much more pleasant I imagine. Parts can be reasonable if you dont buy thru Yanmars extortion network.

What have you got for fuel filtration?
I'd be checking all the fuel connections again & regardless that you got a start with the dodgy injector I'd still repair that.
The head gasket issues are easy to overcome if you use gasket cement on the head gasket. My choice is Loctite 518.
Those engines can be run continuous as they were used for rice paddy field water pumps so worth rebuilding if you are mechanically inclined.


BTW the oil capacity is .92 us gallon & you are fine to use 15w-40 Cf diesel oil in it but I guess you already know that



Be interesting to hear if it goes 2mrw.

[rockin411]

Day 3 update: A little slow to start but only advanced the throttle about 1/4 and it started on second key try. It usually started from idle every time.

I then shut it down and it restarted immediately and ran fine for about 5 minutes before shutting it down and working on other projects. About 2 hours later it started with no problems but ran for a few minutes then slowly started to slow down until it stopped. Tried starter fluid again but no luck. It won't start now. Ideas?

Removed injector again and here it is at idle:

https://www.youtube.com/watch?v=4a9u...ature=youtu.be

[bglad]

Not sure if it has anything to do with the current issue but is there not a vented loop on the engine raw-water system? Most sailboat engines are near enough or below the waterline to need one (see video post #19).

[Compass790]

Yep it still sounds like a fuel/air issue but not guaranteed. The injector spray looks better in that vid which begs the question why was it dodgy in last vid?
Is the fuel lift pump ok? You could try rigging up a gravity feed of filtered fuel direct to injector pump.
Bit strange that it wont start with starter fluid.
Have you taken rocker cover off yet & checked valve operation & clearances just to rule them out.
Need to check exhaust port still as well.

[Wotname]

Originally Posted by rockin411

Day 3 update: A little slow to start but only advanced the throttle about 1/4 and it started on second key try. It usually started from idle every time.

I then shut it down and it restarted immediately and ran fine for about 5 minutes before shutting it down and working on other projects. About 2 hours later it started with no problems but ran for a few minutes then slowly started to slow down until it stopped. Tried starter fluid again but no luck. It won't start now. Ideas?

Removed injector again and here it is at idle:

If it has enough compression to start, it has more than enough to keep running!

This does sound like a fuel or air problem.

Let me endorse Compass790 points -

• check the valve lash / tappets; even if unlike to the problem, this easy to do and should be done.

• Check the exhaust 'manifold' and water injection point for blockages, not just the exhaust hose

Next, can you hear the injection 'squeak' when you turn the engine over by hand, decompressed and at WOT? This is important, if the 'squeak' is weak or non existent, you MUST adjust the regulator. Failure to do so will result in hard starting and poor running. The procedure is outlined in the Operator's manual. I have attached the relevant page. It is not difficult except maybe for the first time!

This regulator adjustment is located below the air intake.

[rockin411]

check the valve lash / tappets; even if unlike to the problem, this easy to do and should be done.

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.

I had taken the exhaust cover off recently because I had an oil/carbon leak so I cleaned all of that that as best as I could - that's why I have the pink tape on the threads. Also removing the exhaust cover is a pain because the mixing elbow blocks the bolts so I have to disassemble everything to do it. I posted a question about getting a longer nipple to avoid that in a separate thread.

[rockin411]

Also, y'all helped me with the regulator around this time last year. I had mistakenly assumed I had a fuel pump problem and removed it and disassembled everything. It was a miracle I got it back together with your help. The problem that time was simply that I didn't understand how to bleed the lines. It's been running great all year after that.

If it were the pump or regulator wouldn't the spray be bad?

[Wotname]

Originally Posted by rockin411

..........

If it were the pump or regulator wouldn't the spray be bad?

No, it would not affect the spray pattern but it would affect the amount of diesel contained in the spray pattern.
You would not be able to detect the different amounts by eye.