I know several folks on this forum have spent many hours working on a YSM12. This question is to those who have done this work before. The shop manual appears to indicate that the timing spec for the injection pump is 25 degrees (+ or - 1 degree) before top dead center. Am I reading this correctly?
YSM12 Injection Pump Timing?
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First, I have not had problems with my YSM12 and have not had the pleasure of working on the injector or the injector pump. The YSM8/12 manual states that the injector pump timing is TDC 25 deg +/- 1 deg on page 12 of chapter 3. As far as I know you should not have to worry about it unless you took the camshaft and/or crankshaft apart. This cannot be the real injector timing that is controlled by the camshaft, but the observed crankshaft timing mark at the (starter?) Window. The described shims are used to make small timing adjustments by raising or lowering the injector pump in relation to the injector cam. I can email you the manual pdf file(s) if you do not have a copy. Maybe someone with experience (ie.. Maine Sail) can add more info.
Jalepeno, I have the manual. I installed a brand new injection pump and need to set the timing. I have a set of shims and I have the starter pulled so that I can see the timing mark. 25 degrees BTDC seems extreme and the manual seemed a little vague. So I was hoping someone on the forum had some experience with this.
I think that you should use the same amount of shims that the old injector had and stick the thing back in. The timing of 25 degrees did not change since you took the injector out, as previously stated you have to dissasemble the case to affect that. The + or - comes from the shims.
Seriously, just use the same shim set up as before, I may even use the old ones if I were you, if they look good. Then bleed the system correctly. Then crank and enjoy. Have you bled the fuel system before? It was a bit hard for me to tell if it was indeed bled, until it cranked up that is.
Seriously, just use the same shim set up as before, I may even use the old ones if I were you, if they look good. Then bleed the system correctly. Then crank and enjoy. Have you bled the fuel system before? It was a bit hard for me to tell if it was indeed bled, until it cranked up that is.
This is how I bled the system.
1. I have a tank above the engine in the cockpit locker. I opened the fuel and filled the filter.
2. I used the finger pump on the fuel pump to pump fuel to the injector(the one you are working on). I loosened the banjo fitting while pumping and tightened it while the fuel was flowing to it.
3. I disconnected the hard line with the loop in it at the injector on the head I cranked the eninge until I saw sprts coming out of there. I hooked that back up and cranked it. It started immediately and has ever since.
When I first rebuilt the engine, I didn't bench test it. I just reinstalled it and tried to crank it. I did not bleed the injector properly and it would not start.
I may have done the procedure a few time above, I can't really remember. But when it finally cranked it ran and I never had a problem losing prime. I did have the hard line fuel return that goes back to the little onengine filter rust through. It was leaking all over but the engine still ran fine. I repaired that with some neoprene fuel line a 4 stainless hose clamps.
1. I have a tank above the engine in the cockpit locker. I opened the fuel and filled the filter.
2. I used the finger pump on the fuel pump to pump fuel to the injector(the one you are working on). I loosened the banjo fitting while pumping and tightened it while the fuel was flowing to it.
3. I disconnected the hard line with the loop in it at the injector on the head I cranked the eninge until I saw sprts coming out of there. I hooked that back up and cranked it. It started immediately and has ever since.
When I first rebuilt the engine, I didn't bench test it. I just reinstalled it and tried to crank it. I did not bleed the injector properly and it would not start.
I may have done the procedure a few time above, I can't really remember. But when it finally cranked it ran and I never had a problem losing prime. I did have the hard line fuel return that goes back to the little onengine filter rust through. It was leaking all over but the engine still ran fine. I repaired that with some neoprene fuel line a 4 stainless hose clamps.
Your thoughts are the same as mine. I installed the new injector pump with the old shim pack. It makes sense to me that a new pump would not affect the shims required. I would assume that the shim requirement would be a function of the block and cam and not the pump.
The fuel system is all vented, the new pump is pumping, and ready to check the timing. I failed to take my service manual with me to the boat so I was not certain of the timing spec. When I got home and looked in the manual, I was surprised to see what I thought was the spec. The manual is also somewhat confusing with discussion of checking timing at TDC and then a spec that seems to call for 25 BDTC.
It will be March before I launch the boat and start the engine. I'm just trying to get all of my ducks in a row now.
Thanks for the help.
The timing is gears inside. You don't have to worry about that. But the incremental timing with the shims, the only way I know to test it is to crank it and see how it runs. Good luck with it. I'm sure you will get it running.
Why did you replace the injector in the first place? If it was bad, how did you know it was bad?
Why did you replace the injector in the first place? If it was bad, how did you know it was bad?
I did not send the pump out for testing and did not directly measure it's performance. Over time the engine has gradually reached a point where it will only run at a max rpm of 2400. I went through the process of adjusting the governor and the no-load maximum rpm (no help). I inspected the fuel system (and changed the filters) and exhaust for blockage. Through the process of elimination I decided that the 30 year old injector pump seems to be the most probable cause of the loss of power.
If my troubleshooting logic is wrong, I will still have a problem and a spare injector pump.
It doesn't make sense to me. There are a lot of variables in the pump mechanism. The manual for my Yanmar engine specifically warns not to use the old shim when replacing the pump.
I can't find anywhere in the manual for this engine where it says don't use old shims. The procedures are quite involved for measuring timing, fuel volume delivery, shape of injection, etc. My advice is put it together just like you took it apart, bleed it and see if it runs ok. I tried to have these components tested but the Yanmar facility I took it to said that the engine was too old and the injectors didn't fit in their test benches.
Since you are having poor performance and the fuel system is definitely suspect, if this doesn't solve your problem I would start replacing parts in the injector on the head.
A 'good ' mechanic doesn't just throw parts at an engine and hope it works. But it may be difficult for you to properly diagnose your engine problems due to the age.
I think a good bet is to throw some parts at it. You seem to have the same attitude.
Since you are having poor performance and the fuel system is definitely suspect, if this doesn't solve your problem I would start replacing parts in the injector on the head.
A 'good ' mechanic doesn't just throw parts at an engine and hope it works. But it may be difficult for you to properly diagnose your engine problems due to the age.
I think a good bet is to throw some parts at it. You seem to have the same attitude.
Bud, just a couple of comments.. I don't know a lot about diesels, but if it will run at max governor rpm but will not run more than 2400 under load, AND is not smoking, your injector pump (HP pump) may be worn and not delivering enough fuel. The timing is important in this too, and it may be contributing... but I'd suspect that the engine would smoke from incomplete combustion if it were only the timing. A new pump will have slightly (minutely) differences in the roller and since your cam has worn slightly, the timing may be a bit retarded.. but I'd suspect too much clearance between the plunger and the barrel, causing the pump to not deliver a full fuel pulse.. or something else not allowing the injector to get a full gulp .. Sounds like you've looked at most.. (I have to ask) Is the prop clean and the hull clean?
Background information on the boat:
The boat is in a cradle on the hard for the winter. The 2400 rpm was a no-load maximum. The engine does not smoke and runs as smooth as you can expect a one cylinder engine to run. However, I was not able to reach hull speed at full throttle. The injector has less than 100 hours on it. The engine has less than 100 hours since an extensive rebuild (by me) which included a new head and cylinder liner along with the usual rebuild parts. The hull and prop were relatively clean when the boat was hauled out in November. The engine only had a Yanmar secondary fuel filter when I bought the boat 3 years ago. I added a Racor primary filter 2 years ago. I changed the filters this fall at haul out. There had been less than 25 gallons of fuel to pass through them since the last change. The old filters appeared to be clean. After all of the troubleshooting, I felt that the logical explaination was a clearance issue with the injector pump.
I went down to the boat today and checked the timing per the manual. The timing appears to be very close to 25 degrees BTDC with the old shims with the new injection pump. I checked the timing about a dozen times and recorded some minor variablity. However the average was as close to 25 BTDC as I believe I can accomplish. If I have trouble with it starting in the spring, I will back up and work with the new shim pack. However, right now the timing appears to be correct. I don't plan to start the engine until it is back in the water in March.
Thanks for all of the interest and ideas on this. Owning an old engine is a hobby into itself. I'm glad I enjoy working on old engines.
The boat is in a cradle on the hard for the winter. The 2400 rpm was a no-load maximum. The engine does not smoke and runs as smooth as you can expect a one cylinder engine to run. However, I was not able to reach hull speed at full throttle. The injector has less than 100 hours on it. The engine has less than 100 hours since an extensive rebuild (by me) which included a new head and cylinder liner along with the usual rebuild parts. The hull and prop were relatively clean when the boat was hauled out in November. The engine only had a Yanmar secondary fuel filter when I bought the boat 3 years ago. I added a Racor primary filter 2 years ago. I changed the filters this fall at haul out. There had been less than 25 gallons of fuel to pass through them since the last change. The old filters appeared to be clean. After all of the troubleshooting, I felt that the logical explaination was a clearance issue with the injector pump.
I went down to the boat today and checked the timing per the manual. The timing appears to be very close to 25 degrees BTDC with the old shims with the new injection pump. I checked the timing about a dozen times and recorded some minor variablity. However the average was as close to 25 BTDC as I believe I can accomplish. If I have trouble with it starting in the spring, I will back up and work with the new shim pack. However, right now the timing appears to be correct. I don't plan to start the engine until it is back in the water in March.
Thanks for all of the interest and ideas on this. Owning an old engine is a hobby into itself. I'm glad I enjoy working on old engines.
I have been able to get very close in the past on a calm lake. A little over 4 knots is all I have been to get lately on a calm lake.
When I was motoring from the yard after installing a new prop which was pitched one inch too much, I was able to get 6.2 knots with the wind on the beam. Usually with that prop I would be around 5.2 to 5.5 knots. If there was any chop it would knock it back to 2 knots or less. I installed a prop that was an inch down and now I can motor through chop at 5 knots. But top speed is about 5.2.
What kind of prop and size do you have on your boat now? Mine is 12LH10.
What kind of prop and size do you have on your boat now? Mine is 12LH10.
Bud, Man, 2400 RPM unloaded is pretty short on power.. You've looked at almost everything else (elbow, intake, injector, timing, valve clearance, etc) and it is not smoking from unburned fuel.. it isn't getting enough fuel.. so the pump may be worn .. Another thing to check is the fuel delivery rack gear.. it rotates a part inside the pump that makes the pump deliver more fuel to the injector. It is moved by the governor so it has to be free to move and its travel must not be restricted, it must move very freely, and it must be set per the manual..(match marks).. If the rack were restricted by sludge or deposits, it may not go to full stroke .. which would limit RPM and not smoke, just like a worn pump.. The pump outlet "delivery valve" can have a bad seat and also limit the stroke volume since it would decrease the output volume. I'd be interested to hear what ya find.. Ya might want to pull the pump and take it to a good diesel shop ?? or pull it and do a look-see yourself while she is on the hard??
Sounds like you know what you're doing, so I won't contribute anything, except: YSM12 an "old" engine??? I put in a "NEW" 2GM20 to replace the OLD Volvo MD6A. And the ol' Volvo is sitting under my deck at home, going to be in a 16ft powerboat as soon as I figure out why there's exhaust coming out the intake manifold...
druid - diesels ain't old till they're over 40 anyway
druid - diesels ain't old till they're over 40 anyway
I checked the setting on the gear rack to be sure the marks are lined up properly and the gear rack is moving freely. I have not checked the outlet valve. I have a brand new pump installed in the engine now and have checked the timing. I don't plan to start the engine until the boat is launched in March. I'll report back on how the engine works with the new pump in place.
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